Power Line Communications in Practice
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Power Line Communications in Practice Xavier Carcelle artechhouse.
Library of Congress Cataloging-in-Publication Data A catalog record of this book is available from the Library of Congress British Library Cataloguing in Publication Data A catalogue record of this book is available from the British Library ISBN 13: 978-1-59693-335-4 Cover design by Igor Valdman Translated from the French language edition of: Réseau CPL par la pratique by Xavier Carcelle. ©2006 Groupe Eyrolles, Paris, France.
To Yves, Françoise
Contents Preface xiii Organization of the Book xiii Acknowledgments xvii CHAPTER 1 Introduction 1 PLC Technologies Standard Organizations What Kinds of Standards Are There? Consortiums and Associations Toward a Standardization of PLC Technology Future IEEE Standard Future Interoperability Standard Advantages and Disadvantages of PLC 1 2 4 8 10 10 10 10 PART I PLC Theory 13 CHAPTER 2 Architecture 15 Architecture of Electrical Networks Characteristics of Electrical Wiring Modeling Electrical Net
viii Contents Peer-to-Peer Mode Centralized Mode Transmission Channel Functionalities Access to the Medium Using CSMA/CA Techniques The ARQ (Automatic Repeat Request) Process Synchronization and Frame Controls Managing Frame Priorities Managing Frequency Channels (Tone Map) Segment Bursting and Contention-Free Access Frame Level Functionalities MAC Encapsulation Fragmentation Reassembly Other Functionalities Dynamic Adaptation of the Bit Rate Unicast, Broadcast, and Multicast Service Quality 34 36 38 38
Contents ix MAC Header Format Format of an Encrypted MAC Frame Format of Control and Management Frames 100 102 103 PART II PLC in Practice 105 CHAPTER 6 Applications 107 Voice, Video, and Multimedia Telephony over PLC Visioconferencing and Videoconferencing Multimedia PLC Local Networks Internet Connection Sharing File and Printer Sharing Audio Broadcasting Recreational Applications Video Surveillance Backbone of a Wi-Fi Network InternetBox and PLC New Applications for PLC PLC in Industry PLC in Pub
x Contents Repeaters Filters The Cost of PLC 145 146 148 CHAPTER 8 Installation 151 Frequency Bands Regulation of Radio Frequencies Electromagnetic Compatibility and Frequency Bands Topology of Electrical Networks Single-Phase Wiring Three-Phase Wiring Wiring in an Electrical Network The Circuit Breaker Panel Attenuation on an Electrical Network Choosing the Topology for a PLC Network Propagation of the PLC Signal Interference Effects of Interference on the Electrical Network Network Data Rates Useful
Contents xi Configuring the PLC Gateway Configuring PLC Security Testing Operation of the PLC Network Firewall VPN and PPPoE Configuring an Internet Gateway Sharing the Internet Connection Configuring NAT and DHCP 224 228 230 231 232 235 236 237 CHAPTER 11 PLC for Businesses 247 Network Architecture Supervising a PLC Network Choosing a Standard Choosing Network and Electrical Equipment Service Quality Access to the Electrical Medium Placing Equipment Choosing the Network Architecture Security Paramete
xii Contents CHAPTER 13 Hybrid PLC 295 Coexistence of Multiple Networks PLC Technologies Between Themselves Coexistence of PLC and Wi-Fi Coexistence of PLC and Wired Ethernet Advantages and Disadvantages of Network Technologies Optimizing Network Architectures Example of an Optimized Architecture PLC and Wi-Fi, a Perfect Couple? 295 296 298 304 304 304 306 307 Resources 309 Web Sites Books and Articles 309 311 About the Author 313 Index 315
Preface Since the emergence of the first power line communication (PLC) products in early 2000, PLC technologies have been steadily undergoing great improvement, the aim of which has been to deliver optimum performance. Today, PLC has reached maturity and achieved performances comparable to the other LAN technologies, but with the added advantage of being much easier to deploy.
xiv Preface • • • • • • • • • • • • • Chapter 1. Introduction. This first chapter covers the history of PLC technologies and presents the work carried out by the different working groups (alliances, industrial groups, and so forth) leading their development. Part I. PLC Theory. This part focuses on the characteristics of the electrical and computer networks and details the different functionalities proposed by PLC to stream the data by all possible means to the end user. Chapter 2.
Organization of the Book • • xv Chapter 12. PLC for Communities. This chapter focuses specifically on those communities faced with the issue of providing Internet access in remote areas. This chapter provides solutions and the architecture principles to be followed in a management project for Internet access using the public electrical network. Chapter 13. Hybrid PLC.
Acknowledgments I would like first to extend my appreciation to the people at Artech and namely Simon Pluntree, my editor in chief, and Judi Stone, who have been following and supporting the project. A great thanks goes to Michel Goldberg, whom I consider one of the best experts on standardization in the field of PLC networks. Michel reviewed the content of the book to ensure the quality of the first chapters and gave his great expertise to achieve such a book.
CHAPTER 1 Introduction The PLC (power line communication) designates a technology that uses the medium and low voltage electrical network to provide telecommunication services. Although, since its first applications when the frequency range started at a low level, PLC is today more commonly used for high-frequency applications, also known as broadband powerline (BPL).
2 Introduction (intruder alarm, fire detection, gas leak detection, and so forth). Much less power needed to be injected, since the power was reduced to levels of approximately a hundred milliwatts. The expression “power line carriers,” usually abbreviated to PLC, appeared at the end of World War II in 1945. By that time, many telephone and electrical lines had been destroyed and there were more infrastructure electrical lines than telephone lines.
3 PLC Technologies A “standard” is a document from any national body, such as the IEEE (USA), or from a Community of States, such as ETSI. To make the difference, it is sometimes called “de facto standard.” We will call it “specification.” To give a simple description of the conditions to be fulfilled by a standard, we refer to the definition given by ISO: “Any document designed for a repetitive action, and approved by an acknowledged standardization body and being at everybody’s disposal.
4 Introduction For European countries, this is a fundamental level since the international standards, the specifications of which will be used as a reference for CE marking, are written in the European standardization committees. For a better understanding of the mechanisms for the implementation of international standards in a broad sense, this European standardization organization should be compared with the existing organization in the United-States. Citing the “Overview of the U.S.
PLC Technologies 5 COMPANY STANDARD: Consensus among the employees of an organization. CONSORTIUM STANDARD: Consensus among a small group of organizations, usually like-minded companies formed to undertake an activity that is beyond the resources of any one member. An example of a consortium is the United States Council for Automotive Research’s (USCAR’s) Strategic Standardization Board, which reflects USCAR’s commitment to managing standards issues with regard to competitiveness.
6 Introduction Cenélec and ETSI. This international standard is not aimed at limiting the deployment of wired networks but at limiting their interfering emissions. After five years of trying to find a consensus, and noticing that it is almost impossible to define wired network radiation limits, it was decided to abandon the idea of publishing an international standard for this network, focusing instead on the international standard of the product.
7 PLC Technologies any enforcement measures related to powerline communication systems). The first such report is due on 31 December 2005. 8. This Recommendation is addressed to the Member States. Done at Brussels, 6 April 2005 for the Commission, Viviane REDING, Member of the Commission.
8 Introduction and national standards relating to PLC in Europe, in particular the IEC, Cenélec, and the ETSI. Consortiums and Associations In addition to the bodies and institutions above, some associations and consortiums play a pre-standardization, or even standardization, role for PLC; in particular, the three major parties involved include HomePlug, the IEEE, and the Opera consortium. Historically in Europe, any lobbying in favor of PLC was conducted by the PUA and the PLC Forum. Figure 1.
PLC Technologies 9 The IEEE distributes both information and resources to its members, as well as providing technical and professional services. To stimulate interest in occupations related to the technology, the IEEE also offers services to its student members all over the world. Another major aspect of the IEEE consists of prospects, individuals and corporations, buying its products and participating in its conferences and symposiums.
10 Introduction PLC Forum The PLC Forum is an international body created at the beginning of the 2000s from the merger of two associations. It develops its activities in coordination with other bodies working on PLC. Toward a Standardization of PLC Technology Any standardization is a slow process. This is not surprising if we consider that it requires the consensus of the members of the particular work group before any decision is made.
Advantages and Disadvantages of PLC Table 1.1 11 Main Parties Involved in IEEE PLC Standardization Advanced Communications Networks SA Ambient Corporation Arkados, Inc. CEPCA Administration Conexant Systems, Inc. Corinex Communications Corporation Current Technologies DS2 Duke Power Earthlink HomePlug Powerline Alliance IBM IBEC (International Broadband Electric Communications), Inc. Intel Intellon Corporation Itochu Corporation Mitsubishi Electric Corporation Mitsubishi Materials Ltd.
12 Introduction • • • quick deployment; no additional wiring; a robust encryption method.
PART I PLC Theory This part of the book is devoted to the HomePlug specification. Created by the industrial alliance of the same name, HomePlug focuses on two principal aspects: the physical layer, concerned with data transmission over the power line medium; and the data link layer, which defines the architecture and mechanisms to implement, allowing this transmission to take place over the network under the best possible conditions. Since the release of HomePlug 1.
CHAPTER 2 Architecture PLC, or power line communication, is the generic name for a network technology that transmits data over electrical wiring. It is the result of extensive research on high bandwidth data transmission on the power line medium. The architecture of PLC networks is comparable in many aspects to that of wired networks, but also to that of Wi-Fi networks, as we will see in this chapter. HomePlug was the first PLC specification to provide a bit rate between 1 and 5 Mbit/s.
16 Architecture Table 2.
Architecture of Electrical Networks Figure 2.2 17 Simplified architecture of the electrical distribution network In terms of responsibility, each part of the electrical network is operated by distinct organizations, responsible for supply and transport of electricity, as well as the transport of data in the case of PLC networks. Figure 2.3 illustrates this division of responsibilities as applied to the different organizations composing the national electrical network.
18 Architecture This section introduces some of the physical properties of electrical wiring in order to understand its capabilities (both advantages and limitations) for the transmission of data. Impedance Electrical wiring is characterized by an impedance Z (the absolute value of the resistive, inductive, and capacitive components of the elements in the electrical network). It is not a fixed value. Devices are constantly being connected or disconnected from the electrical wiring.
19 Architecture of Electrical Networks also be expressed in terms of electrical flux (φ) and associated with the electrical potential between the two surfaces of the dipole: C= φ (expressed in coulombs) V In the case of a sinusoidal voltage (as is the case for household electricity), this equation is expressed efficiently using Ohm’s law, as a function of the voltage (U), current (I) and frequency (f): C= I (expressed in farads) U2πf The impedance (Z) of an electrical circuit is composed of resistive
20 Architecture • harmonic noise, composed of multiple frequencies used by electrical equipment connected to the network and which are multiples of the line frequency (for example, 50 Hz yields harmonics of 300 Hz, 600 Hz, and so forth). Overall, the noise is quantified by the signal-to-noise ratio, or SNR, generally measured in decibels (dB).
21 Architecture of Electrical Networks The signal frequency of a HomePlug 1.0 modem is between 4 and 25 MHz, giving a power spectral density of –50 dBm/Hz. We will examine the consequences of this value in Chapter 8 (Table 8.10). Table 2.2 summarizes attenuation values for the principal devices on the electrical network. Multiple studies have shown that in a household electricity distribution network, the average signal attenuation is on the order of 50 dB/km.
22 Architecture Depending on the electronic components used, the analog interface has a characteristic “sensitivity” that affects its ability to transmit the PLC signal without excessive degradation. This sensitivity is modeled by an impedance between the electrical wiring and the digital circuitry of the device.
23 Architecture of Electrical Networks Work by Nicholson and Malak has allowed us to express the average impedance of an electrical line by the formula: Zc = L C where L = μH/m (linear inductance of the electrical line) C = μF/m (linear capacitance of the electrical line) Work by Downey and Sutterlin has allowed us to model the electrical circuit equivalent to an electrical line. This circuit, composed of resistances, inductances and capacitances, may be schematized as shown in Figure 2.5.
24 Architecture With the exception of EMTP, which allows modeling an entire electrical network and all its wiring as a function of its topology, there exist few tools capable of facilitating the engineering and the understanding of the behavior of PLC signals on electrical wiring. However, Cenélec (the European Committee for Electrotechnical Standardization) is developing a system to facilitate the modeling of in-home electrical networks.
Architecture with a Shared Medium Figure 2.6 25 The public electrical network viewed as a shared medium main circuit breaker panel, and the PLC signal circulates in all branches by passing through the panel. Figure 2.7 illustrates a simplified example of an electrical network with three branches from the circuit breaker panel. On the right side of the illustration, the PLC signal propagates between all the outlets, thereby connecting the PLC devices.
26 Architecture Figure 2.7 A private electrical network viewed as a shared medium Figure 2.8 Analogy between a PLC network and a hub At points in the electrical wiring where the PLC signal becomes too weak to be used by the network’s PLC devices, the repeater amplifies and regenerates the signal. Two different types of repeaters allow us to extend the range of PLC networks: • “Physical” repeaters literally amplify the signal and retransmit it along the electrical line.
Layered Architecture • 27 signal and not on the data frames. Therefore, this type of repeater does not reduce the bandwidth of the overall PLC network. “Logical” PLC repeaters repeat the signal at the level of the data frames. This type of repeater is composed of two PLC devices connected by their Ethernet interface.
28 Architecture Figure 2.9 Figure 2.
29 Layered Architecture Figure 2.11 Frequency bands allocated to PLC networks Two frequency bands are allocated to PLC technologies: • • 3 to 148 kHz for low bit rate PLC; 2 to 20 MHz for high bit rate PLC. Figure 2.11 illustrates the placement of PLC frequency bands relative to those of other network technologies.
CHAPTER 3 Functionality The functionalities of the PLC networks are introduced in this chapter. The technologies used in these networks are simple enough to be integrated into a single chip so that components can be manufactured at a very low cost. They will still be relevant up to the introduction of new PLC interfaces making it possible to increase the throughput of the devices.
32 Functionality • • Peer-to-peer mode. May be compared to a peer-to-peer IP network, where all the PLC devices of the network play the same role and have the same hierarchical level. These devices may have interchanges without being monitored by a master device. Centralized mode. Blending of the two preceding modes, in which a centralizing device is responsible for managing the network and exchanges between PLC devices.
33 Network Mode Functionality • • • numbers of bits/Hz, and so forth). This QoS management is ensured by using a quality table for the various links located at the PLC master level. Possibility to create VLAN or slave inter-device links via the centralized administration of encryption keys at physical and possibly logical levels. Device supervision in order to integrate IP network administration tools (SNMP stack type) upstream in the PLC network according to a more complete IP network architecture.
34 Functionality Peer-to-Peer Mode The telecommunication network theory has been much based on the network device hierarchy principle. This principle was put into question with the emergence of ad hoc type architectures, either in wireless local area networks or networks for file exchange over the Internet, called peer-to-peer networks. The decentralized networks offer many advantages in comparison with hierarchical networks or networks in the master-slave mode.
35 Network Mode Functionality • • Selection of the best suited modulation mode and FEC (forward error correction) type in view of the PLC link qualities. In the case of HomePlug 1.0, the four possible modes are DQPSK ¾ (differential quadrature phase shift keying), DQPSK ½, DBPSK ½ (differential binary PSK), and ROBO (robust OFDM), which are used to obtain four types of data rates. Priority of each network PLC device.
36 Functionality HomePlug 1.0 PLC Network Hierarchy by Means of Priorities Within IEEE 802.3 Ethernet frames, a VLAN field may be placed described in the IEEE 802.1Q standard. Within the framework of PLC networks in peer-to-peer mode, this field is used to create almost a hierarchy between the PLC devices of the same network. The field is encoded on 3 bits and therefore can have eight values. Table 3.3 lists the four available PLC priorities according to the value of the VLAN field.
Network Mode Functionality Figure 3.3 Organization of a PLC network in the peer-to-peer mode Figure 3.4 Architecture of a PLC network in centralized mode 37 The data is communicated between the PLC1 and PLC2 devices in the following way: 1. PLC1 and PLC2 put in place an estimate of the transmission channel (modulation levels, error coding level, and so forth). 2. PLC1 and PLC2 inform CCo (PLC3) that they wish to exchange data. 3.
38 Functionality If managing the medium access is handled by the CCo centralizing device like in the master-slave mode, the data is exchanged directly between the devices as in the peer-to-peer mode. Transmission Channel Functionalities In PLC, the transmission channel is the electrical network. Since it was not originally designed to support network applications, network functionalities had to be added to so that the data link layer could be implemented correctly.
Transmission Channel Functionalities 39 increases when a station could not emit, making it possible to bring the use of the network in line with this priority level. Figure 3.5 illustrates the operation of the CSMA/CA algorithm in its entirety. Listening to the Medium In PLC, the medium is listened to both at the physical layer level with the PCS (physical carrier sense) and at the MAC layer level with the VCS (virtual carrier sense).
40 Functionality Two types of mechanisms are used in the VCS: • • detection of fields at the beginning of the frame; wait for response information provided by the frame control fields. Figure 3.6 illustrates these two medium listening techniques before the data frames are transmitted over the electrical network. Access to the Medium The access to the medium is controlled using a mechanism called IFS (interframe spacing).
41 Transmission Channel Functionalities • • RIFS (response interframe spacing). When a station waits for a response from the destination station, the latter waits for a RIFS time of 26 μs before transmitting its response. This RIFS is also used by the stations to change from sending mode to receiving mode. EIFS (extended interframe spacing). The EIFS corresponds to the maximum time that is necessary for a station to transmit.
42 Functionality • frames coming from the source station from the response frames coming from the destination station. RGIFS (reverse grant interframe spacing). Used for frame separation in the Reverse Grant network mode specific to the HomePlug AV standard. Back-off Algorithm As explained above, the PLC uses the CSMA/CA method to control access to the transmission channel.
43 Transmission Channel Functionalities Figure 3.7 illustrates the variation of the contention window (CW) and of the transmission failure counter (DC) according to the number of retransmissions. These values change from an initial value to a threshold value, which generally indicates an overall problem with the network over which the station wants to transmit. When the medium becomes free again, and after a CIFS and frame prioritization phase, the stations make sure that the medium is still free.
44 Functionality If CW and DC reach their maximum value defined by the HomePlug 1.0 standard, these values are maintained, even if the BPC is decremented. As explained above, when the algorithm is used, the stations of the same network have the same probability of accessing the medium. The only drawback with this algorithm is that it doesn’t guarantee a minimum time. Therefore, it is difficult to use within real-time applications such as voice or video.
Transmission Channel Functionalities 45 Data Transmission Example When a source station wants to transmit data to a destination station, it makes sure that the medium is not busy. If no activity is sensed during a time period corresponding to a CIFS, the source station waits for the prioritization period then transmits its data. Figure 3.9 illustrates the role of the timers during the transmission of a data frame and its acknowledgment. If the medium is busy, the station waits until it is free.
46 Functionality The destination station can resend three types of acknowledgment frames: • • • ACK. The destination station has correctly received the data contained in the frames and this data is correct. NACK. The destination station has correctly received the data but some data is damaged. This check is carried out using the CRC (cyclic redundancy check) value. The destination station then asks the source station to resend the damaged data segment. FAIL.
Transmission Channel Functionalities Figure 3.11 47 Frame check using the FCS and RFCS fields in the ARQ process ACK Response In the case of an ACK acknowledgment by the source station, the destination station resends to it a response frame containing the RFCS field of the data frame transmitted by the source station.
48 Functionality NACK Response In the case a NACK type acknowledgment, the destination station resends to the source station a response frame after a contention period in order to indicate that the data has been damaged during the transmission. The source station resends in its turn to the destination station a confirmation of the NACK acknowledgment and retransmits the damaged data frame segment (see Figure 3.13).
Transmission Channel Functionalities Figure 3.14 49 FAIL response in HomePlug 1.0 SACK Response in HomePlug AV In the AV version of the HomePlug standard, an additional response, the SACK (Selective ACK) response, has been added to compensate for the fact that the PLC links between two stations are not necessarily symmetrical in terms of useful throughput. Due to the characteristics of the electrical network, the data transmissions are not under the same influences in one direction as in the other one.
50 Functionality Figure 3.15 Frame check sequence (FCS) Figure 3.16 Management of interframe spaces Synchronization of HomePlug AV Frames Recent PLC developments made it possible to improve the performance of the devices while keeping the interoperability with the devices of previous versions.
Transmission Channel Functionalities 51 lish the specifications of the HomePlug AV (for Audio and Video) version which is much more efficient for the management of the quality of service (QoS). Figure 3.17 illustrates the organization of the beacon frames in HomePlug AV. This standard, based on a master-slave architecture, uses CSMA and TDMA medium access functionalities.
52 Functionality Figure 3.18 Frame priority management by the CAP (channel access priority) variable The CAP variable is used by a PLC station to inform the other stations of its medium access priority. This variable determines the values of the PRP1 and PRP2 priority frame data that is read by the network PLC stations to determine the various priority levels. Therefore, the other stations are informed in advance of the priority of each of the PLC devices.
Transmission Channel Functionalities Figure 3.19 53 Tone map management between PLC devices the number of possible PLC stations in the same PLC network (16 stations for HomePlug 1.0 and 1.1 and 250 stations in HomePlug AV). Some values are reserved for the ROBO mode or for particular implementations of the HomePlug 1.0 standard.
54 Functionality Data frame size (number of blocks with 40 OFDM symbols and next blocks with 20) Figure 3.20 HomePlug 1.0 start delimiter details and associated tone map Figure 3.21 Segment bursting mode management Frame Level Functionalities It is important to remind the structure of the data frames transported over the electrical network in order to understand the network functionalities of the PLC technologies.
Frame Level Functionalities 55 The network modeling into seven layers according to the OSI model makes it possible to understand how the PLC technologies structure data exchanges for each protocol layer. The PLC technologies come into play at the PHY and MAC layer levels only. Because of this, they are considered as IEEE 802.3 Ethernet networks from their interfaces. Therefore, the network engineers only have to consider the IP, TCP, and application configurations seen by the user of PLC technologies.
56 Functionality Figure 3.23 MAC encapsulation in HomePlug 1.0 Fragmentation Reassembly In a PLC transmission using a shared medium disturbed by other uses with a wired Ethernet link using a cable dedicated to data communications, the error rate for the electrical wiring is higher (10–5 for the electrical wiring against 10–9 for the Ethernet cable).
57 Other Functionalities Pair Pair = Source Address, priority Figure 3.24 Data frame fragmentation the destination station or is damaged when it is received, NACK (non-acknowledgment) or FAIL (failure) processes are implemented between the source station and the destination station prior to the resending of the missing or damaged segments.
58 Functionality This is achieved with the dynamic adaptation of the data rate at the physical level according to the quality of the PLC links. Optimum use of the global bandwidth can also be made by sending the data only to the PLC devices involved. These functionalities correspond to those found in other network technologies, such as Wi-Fi. Dynamic Adaptation of the Bit Rate As indicated before, the PLC technology permanently readjusts the condition of the links between network stations.
59 Other Functionalities The unicast mode is also possible: since the PLC stations are identified by their MAC address, if a station knows the MAC address of another station, it can address the MPDU directly and solely to this station. Service Quality The quality of service, which has become very important in IP networks, is used to differentiate the priorities of the various traffic over the network.
60 Functionality delimiter and response frames is used to prioritize the frames with respect to those of the stations with the same priority level or a lower priority level. Using VLAN Labels The use of VLAN labels is compatible with PLC technologies, since the value of these labels is interpreted in the value of the PLC station CAP parameter.
CHAPTER 4 Security Security has been the main problem for Wi-Fi networks. In the case of PLC, this is not so much of a concern as it is difficult to have access to the physical medium. In Wi-Fi, as the transmission medium used is radio, anyone in the network coverage area can intercept its traffic or even reconfigure the network at will.
62 Security to send data; and integrity control, which is used to know whether the data sent was not modified during the transmission. Cryptography Making a text or message incomprehensible through the use of an algorithm is not new. The Egyptians, like the Romans, employed methods used to encode a text or a message. These techniques, which were relatively simple originally, have changed, and cryptography has been recognized as a science since World War II.
Overview of Network Security Issues Figure 4.2 63 Symmetric-key cryptography Various symmetric-key cryptography algorithms have been developed, in particular DES (data encryption standard), IDEA (international data encryption algorithm), series RC2 to RC6, and AES (advanced encryption standard). DES (Data Encryption Standard) The DES algorithm was jointly developed in the seventies by IBM and the NSA (National Security Agency). The DES is an encryption algorithm known as “by blocks.
64 Security However, the DES hasn’t been used since 1998 as its reliability was considered to be poor. Its encryption algorithm has been altered and improved. 3-DES 3-DES, or triple-DES, uses three DES one after the other. Therefore, the data is encrypted then deciphered then encrypted with two or three different keys. The size of the 3-DES key may be 118 bits in size. Because of this, it cannot be used in France. 3-DES is considered as being reasonably secure.
Overview of Network Security Issues 65 RC5 and RC6 RC5, another proprietary algorithm of RSA Security, is an encryption algorithm in blocks with a variable block size between 32 and 128 bits, a variable round number between 0 and 255, and a dynamic key length between 0 and 2,040 bits. RC6 is an improved version of RC5 so therefore uses its characteristics. The only difference relates to the addition of new mathematical operations at the rounds.
66 Security the next round. At the end of the last round, which does not require transformation mechanism M, the data block is considered encrypted. Once all the blocks for a given message are encrypted, they are reassembled in order to create the encrypted message that can then be transmitted over the network. The AES encryption procedure is illustrated in Figure 4.3. Decryption is the opposite process of encryption as illustrated in Figure 4.4. AES, which was used by the U.S.
Overview of Network Security Issues Figure 4.5 67 Public-key cryptography As with symmetric-key cryptography, various algorithms are used, in particular RSA (Rivest, Shamir, Adelman) and Diffie-Hellman. Though this technique makes it possible to compensate for the shortcomings of symmetric cryptography, i.e., key transmission, it is much slower than symmetric cryptography.
68 Security Mixed-Key Cryptography Mixed-key cryptography, illustrated in Figure 4.6, uses the two aforementioned techniques, i.e. symmetric-key cryptography and public-key cryptography. It combines in this way the advantages of the two techniques while avoiding their disadvantages. Their disadvantages are well known, as symmetric-key cryptography does not enable secured key transmissions and the public-key cryptography uses algorithms that are too slow for data encryption.
Overview of Network Security Issues 69 A message to be sent can be signed using various techniques. One of them uses public-key algorithms but hash functions are mostly used. Use of Public Keys In addition to confidentiality, public-key cryptography has the advantage of allowing message sender authentications. The electronic signature is the second use for public keys. For authentication purposes, the sender uses his or her private key to sign a message.
70 Security Figure 4.8 illustrates a sender who wishes to send a message while making sure of its authenticity. For this purpose, a message digest is created by the sender by means of hash function H. The message and its digest are sent to the recipient applying the same hash function H to the received message in order to compare the new digest with the received digest. If the digests are the same, this means that the message has not been modified.
Overview of Network Security Issues Figure 4.9 71 Hash and public key Various hash techniques are used, in particular the following ones: • • MD2, MD4, and MD5. Message digests 2, 4, and 5 were developed by Ron Rivest for RSA Security. These are hash functions that all produce digests with a size of 128 bits. MD2 is the most reliable but is optimized only for 8-bit machines, whereas the other two are optimized for 32-bit machines. MD4 was abandoned since it is too sensitive to certain attacks.
72 Security • • • • • Brute force attack. This attack consists of working through all the possible combinations in order to recover a password or an encryption key used in a network. Dictionary attack. This attack is used to recover a password or a key by using a database containing many words. Spoofing attack. This attack is based on identity usurpation in order to access the network.
Security for PLC Networks 73 Therefore, a PLC logical network is based on an encryption key called a NEK (network encryption key) in the HomePlug specification that encrypts the data exchanged between the various PLC devices (see Figure 4.10). A PLC network can be configured with a NEK in several ways: • • • Via the Ethernet interface. A configuration frame of the NEK is sent in broadcast mode to the PLC devices of the same network using a configuration tool.
74 Security However, several more or less realistic techniques are used to have access to the data exchanged over a PLC network; in particular, these techniques consist of: • • • Using a PLC device with the suitable NEK key for the targeted network. Recovering the physical data via the electromagnetic radiations emitted by the PLC network in the environment close to the electrical wiring. However, this requires a complex and costly acquisition chain.
Security for PLC Networks 75 Access to Physical Frames The data exchanged over a PLC network is carried in PLC frames known as “physical frames.” The PLC frames circulate over the electrical network between all the outlets in encrypted form. As explained above, it is difficult to have access to the physical medium.
76 Security Figure 4.12 Access of a device to a PLC network identified by its NEK key The NEK identifies the PLC network in the same manner as the WEP (wired equivalent privacy) is used to protect the data of a Wi-Fi network. It also carries out the following tasks: • • • creation of several PLC networks on the same electrical network; encryption of the data flowing between the PLC devices; and authentication of the devices belonging to the PLC network.
Security for PLC Networks 77 Calculating the NEK The PKCS#5 standard specifies two methods for the implementation of a cryptography derived from passwords. The PBFDK1 method was chosen in HomePlug. As input parameters, it demands a password (entered by the administrator); a “salt value” (constant parameter specified by HomePlug which is a kind of public key); an iteration count, i.e.
78 Security m is the input message of arbitrary length converted to a bit stream. mpad consists of pad bits (1 followed by 0’s) concatenated to m such that the length of mext is congruent to 448, modulo 512. ml is the length, in bits, of the original message, m, expressed as 64-bit binary blocks. The extended message, mext, is subjected to four rounds of bit transformations where each transformation includes 16 operations. On each operation, a fixed value is added to the result.
Security for PLC Networks 79 Table 4.1 Encryption-Key Management According to PLC Technology KEY TECHNOLOGY ENCRYPTION ADVANTAGES MANAGEMENT DISADVANTAGES AND FLAWS HomePlug 1.
80 Security We notice that this technique requires too much time to be used efficiently. Denial of Service Attacks The purpose of an attack is not necessarily to crack an encryption algorithm to recover the key and listen to the network or get into it. The single purpose of some attacks is to sabotage the network by preventing it from operating. This type of attack, called denial of service, or DoS, is widespread for all network types.
IEEE 802.1x and Improvements to PLC Network Security Figure 4.13 81 IEEE 802.1x authentication architecture RADIUS and Diameter 802.1x does not define a particular authentication protocol on the server side. Two client-server authentication protocols, RADIUS and Diameter, can be used. The simplest one, RADIUS, has become the default server of any 802.1x architecture.
82 Security • • • Apart from encryption, EAP-TLS has the same characteristics as TLS but these are encapsulated into EAP packets. EAP-TTLS. EAP-TTLS (tunneled TLS) is a Funk Software solution based on the use of two tunnels; the first one is used for authentication purposes by EAP-TLS and the second one to secure transmissions with an authentication method left to the choice of the manufacturers (EAP-MD5, PAP, CHAP, and so forth). PEAP.
IEEE 802.1x and Improvements to PLC Network Security Figure 4.14 RADIUS negotiation Figure 4.15 Exchange of EAPoL messages between an access point and a station 83 The authentication is always initiated by the station which sends an EAPoL-Start request. The access point transmits to it one or several requests to which it must respond.
84 Security message; in this case, the station is not authenticated. The station can deauthenticate itself at any time by sending an EAPoL-Logoff request. 802.1x uses an authentication server to which the access point relays information, as shown in Figure 4.16. The authentication phase can only be initiated by the station. After having received the authentication request, the access point requests the station to identify itself with an EAP-Request (Identity).
IEEE 802.1x and Improvements to PLC Network Security 85 Virtual Private Networks The purpose of the virtual private networks, or VPN, is to provide an end-to-end secured tunnel between a client and a server. VPN are used, among other things, to identify and to authorize access as well as to encrypt any traffic flowing in the network. To date, IPsec is the protocol that is the most used in VPN.
CHAPTER 5 Frames To send information, the PLC stations must prepare data frames, i.e., data blocks with a header and an area indicating the end of the frame. The block containing the user data has a specific format that depends on the technique used in order to access the physical medium used. As the power line medium is shared, a technique used to circulate multiple frames coming from various machines must be determined.
88 Frames This chapter discusses the structure of the PLC frames used in HomePlug 1.0 and introduces the main characteristics of the frames in HomePlug AV. Physical Layer Frames If we observe the complete structure of the HomePlug 1.0 physical layer frame permanently exchanged between the PLC devices (see Figure 5.2), we notice that it consists of a number of elements surrounding the long data frame including the data of the higher level protocol layers from the OSI model’s point of view.
89 Physical Layer Frames Figure 5.3 illustrates the respective times of these various OFDM blocks. The complete frame time is defined by adding the various OFDM symbol block times. The maximum possible transmission speed and the bit rate concerning the data link layer can be calculated in this way. With a 2,705-byte frame, the maximum transmission speed is obtained in the following way: Bit ratePHY_MAX = 2,705 × 8 bits/1,534.86 μs = 14.
90 Frames Improved transmission speeds are predicted with the evolution of PLC technologies, as indicated in Table 5.3. Architecture of the Physical and Data Link Layers of HomePlug AV The latest technical developments by the HomePlug consortium have led to improvements in HomePlug 1.0 performance in the new HomePlug AV version. The architecture of the physical layer and of the data link layer has been modified while allowing interoperability with the HomePlug 1.
The OFDM Interface Frame 91 The OFDM Interface Frame The OFDM (orthogonal frequency division multiplexing) interface is the access technique used by PLC. This access technique is also used by Wi-Fi in the IEEE 802.11a and 802.11g standards and by the ADSL and terrestrial TV broadcasting technologies. This technique is highly robust with regard to communication media interference.
92 Frames Each frequency sub-band conveys OFDM frames comprising two main parts: • • The CP (Cyclic Prefix) is used for the temporal delimitation of the part conveying the data. The data frame consists of OFDM symbols, each of which consists of 428 samples. The OFDM blocks of the HomePlug frame consist of 20 or 24 symbols. Those of the ROBO frame only comprise 40 symbols. Figure 5.6 gives details on an OFDM symbol and the respective times for its various parts: 8.4 μs for HomePlug 1.0 and 40.
The OFDM Interface Frame 93 noise can affect some symbols. In the OFDM technique, symbol losses in a carrier do not affect other carriers. • High bit rate allocation flexibility for each user or each carrier. Each carrier can be encoded independently from the other ones according to the quality of the physical links and to the best suited modulation techniques. • Improvement of the transmission channel preliminary estimate.
94 Frames The 917 frequency sub-bands at the physical layer are used by HomePlug AV. Each band then uses OFDM symbols in order to encode the data in an orthogonal manner in the frequency domain. Therefore, the bands are independent in terms of frequency and do not interfere with each other. In each frequency band, the data and its OFDM symbols are encoded using a turbo convolutional code. The modulation is then carried out; it is potentially different for each frequency band (see Figure 5.8).
The OFDM Interface Frame Figure 5.9 95 Functional blocks for data signal processing in HomePlug 1.0 Differences Between HomePlug Frames and 802.11b Frames From a functional point of view, there are a few differences between the various parts of the HomePlug 1.0 frames and the IEEE 802.11b frames. The main difference concerns the MAC encapsulation of the PLC technologies. MAC type data are defined in it in complete frames, whereas the IEEE 802.
96 Frames The PLC Physical Frame In HomePlug 1.0, the physical layer frames, or PHY PPDU (physical protocol data unit) are strongly related to the MAC layer frames, as some MAC layer information is available at the PHY layer level. There are two PPDU types at the physical layer level: a long PPDU and a short PPDU, as well as a number of elements delimiting these PPDU or allowing sufficient spacing between them so that the stations have the time to transmit or receive the frames.
97 The OFDM Interface Frame • • • • • • The preamble included in the SOF indicates the timestamps of the MAC type frames. FC (Frame Check) is used to check the frame. The frame consists of four OFDM symbols that are highly resistant to the noise on the transmission channel and use a turbocode convolutional code. This code is widely used for signal processing in HomePlug AV.
98 Frames Physical Frame Start Delimiter The start delimiter contains two parts, the preamble and FC: • • The preamble contains the frame sending time stamp.
The OFDM Interface Frame Figure 5.14 Physical frame data body Figure 5.15 End of frame fields of physical frame • • 99 Contention check used to check the state of the contention periods between frames. Delimiter type specifying whether the delimiter is at the beginning or at the end of the frame.
100 Frames • • Variable field specific to this delimiter, which contains the priority level of the PLC station (indicated by the CAP parameter). FCS, which uses a 16-bit CRC for the frame integrity check. The FCS is calculated both on the frame header and body. The techniques used in FCS are usually defined in the main standards on frame transport over a link.
MAC Layer Frames Figure 5.16 • • • • • • • • 101 HomePlug 1.0 MAC frame header Protocol version. Defines the value of the protocol used. This value is reserved and will only be used during a standard evolution. Bridged. Indicates whether the PLC station transmitting the data is in bridge mode and has the potential for relaying the frames to other network stations. MCF (multicast flag). Indicates whether the frames are sent in multicast or broadcast mode by setting this value to 0b1.
102 Frames The 48-bit address consists of the four following parts: • • • • Individual/Group (I/G). The first bit indicates whether the address is an individual (1) or group (0) address. Universal/Local (U/L). The second bit indicates whether the address is a local (1) or universal (0) address. If this is a local address, the following 46 bits are locally defined. Organizationally unique identifier. The number assigned by IEEE corresponding to the 22 bits following the I/G and U/L bits. Serial number.
MAC Layer Frames Figure 5.17 • • 103 Encrypted HomePlug 1.0 MAC frame details IV (initialization vector). Initialization vector with a block of bits concatenated with the block of main data used for decrypting frames. The IV is reinitialized after each use. The combination of IV and data creates a unique encryption key. EKS (encryption key select). Index used to retrieve the NEK used for frame decryption.
104 Frames Figure 5.
PART II PLC in Practice The first part of the book introduced the architecture of PLC networks and explained how they operate from a theoretical point of view. This second part, focused on practice, details the rules to follow when installing such networks by putting the emphasis on the new application possibilities brought about by concepts relating to data broadcasting over an electrical network as well as on the electrical constraints and choosing, installing, and configuring the devices.
106 PLC in Practice lation phase takes place. A number of constraints must be respected in this phase, such as the electrical network topology, security, and performance. By following the advice and configuration procedures explained step by step throughout the chapters of this section, the reader will then be capable of installing and configuring without assistance a PLC network in the best possible conditions.
CHAPTER 6 Applications Many prospective studies show that, in a few years from now, Ninety percent of the networked terminals will not be computers. This prospect shows that many electrical and electronic devices of any type in many fields (industry, hospitals, home automation, electronics, digital arts, and so forth) will be fitted with an RJ-45 network interface used for connecting to a local area Ethernet network.
108 Applications Telephony over PLC The bit rate is not a problem in itself to convey telephone speech, since it can be as low as 5.6 Kbit/s and that such a value is supported by PLC networks to a large extent. On the contrary, since telephony application is interactive, more than 300 ms must not elapse between the moment when the information is sent by a user and the moment when it is received by the recipient.
Voice, Video, and Multimedia 109 The access method used to obtain the right to transmit to the access point, the CSMA/CA (carrier sense multiple access/collision avoidance), makes the PLC network crossing time random. In addition, to reach the recipient, the packets must cross wider networks and go via intermediate transfer nodes that are also crossed randomly.
110 Applications Transit Time In PLC, the waiting time to access the power line medium can be relatively long. If, for example, five clients are connected to the same electrical network by using 1,500-byte frames and integrating access times related to CSMA/CA, a waiting time on the order of 10 ms, or even more, is obtained.
Voice, Video, and Multimedia Figure 6.2 111 Devices crossed by a PLC digital speech stream nal to another one in the same PLC network. After going across the outgoing PLC network, the stream of telephone packets is routed in a fixed IP network, which can be an operator network, then goes via a dedicated gateway, PABX IP, before crossing the conventional telephone infrastructure.
112 Applications Video Video is another application that should develop in the future in PLC networks. This application especially requires a high rate that becomes accessible in PLC environments. Depending on the video application type being considered, the time constraint is more or less strong. The two main cases, streaming video and videoconferencing, are examined below.
Voice, Video, and Multimedia 113 Necessary Rates for Video Routing The video devices mainly use the most recent MPEG standards. DVB (digital video broadcasting) is also widely used. MPEG uses inter- and intraframe compression algorithms. The rate can be as low as 1.5 Mbit/s for television quality with very few losses in comparison with the original image. New developments improved the image quality with bit rates for MPEG-2 of around 4 Mbit/s.
114 Applications several tens of seconds if this is necessary. In this case, once the streaming application is started, the first image only appears at the end of this latency. Visioconferencing and Videoconferencing Visioconferencing and videoconferencing are applications with human interactivity, which requires a 150-ms latency. As explained previously, the data resynchronization process must be observed to reconstitute the isochronous application to the receiver.
PLC Local Networks 115 ited to a factor 3. This is the case of imaging applications, in which the quality is essential, such as X-ray radiographies, for example. Factors varying from 10 to 50 for fixed images and from 50 to 200 for video are obtained. The compression average is 20 for fixed images and 100 for video. These compressions distort the image very slightly but use the recovery capacities of the human eye. This is because the eye is much more sensitive to luminance, i.e.
116 Applications Table 6.1 Subscriber Premises PLC Network Utilization Scenarios NECESSARY APPLICATION UTILIZATION SCENARIO BIT RATE Lone couple Couple with three young children Couple with a young child and two teenagers Qty Bit rate Qty Bit rate Qty Bit rate 22 to 28 Mbit/s 1 22 to 28 1 22 to 28 1 22 to 28 IPTV 3 to 7 Mbit/s 1 3 to 7 3 9 to 21 2 6 to 14 Home theater digital audio system 5.4 Mbit/s 1 5.4 1 5.4 1 5.4 Digital audio CD 2 × 0.8 Mbit/s 3 4.
PLC Local Networks 117 Figure 6.4 Internet connection sharing Figure 6.5 File and printer sharing in a PLC local area network Ethernet interface (RJ-45 connector). From then on, the other users can use it as a network printer with its IP address.
118 Applications Audio Broadcasting A PLC local area network enables data broadcasting over the electrical network including audio data (see Figure 6.6) originating from various sources, in particular the following ones: • • Audio file servers. The files are in MP3 or WAV format and are sent over the electrical network to be retrieved by PLC devices connected to the installation hi-fi devices. Hi-fi system. The audio signal from one hi-fi system to another or to audio speaker systems can be shared.
InternetBox and PLC Figure 6.7 119 Video surveillance on a PLC local area network Backbone of a Wi-Fi Network As we’ll see in Chapter 13, dedicated to hybrid networks, each computer network technology has advantages and disadvantages. A radio computer network that provides both mobility and flexibility to the users within the building where the network is installed can be built with Wi-Fi.
120 Applications Figure 6.8 • • • PLC local area network used as the backbone of a Wi-Fi network Voice. Telephony over IP services. The InternetBox behaves like a telephone receiver to which the analog telephones used on the switched telecommunications network (STN) are connected. Video. IPTV for the broadcasting of TV channels over IP networks and video on demand (VoD). IP services. Domestic mobile telephony, home automation (like electrical power management and family server), and so forth.
New Applications for PLC Figure 6.9 • • • • 121 InternetBox and PLC set-top boxes; TV decoders; electrical over-plugs; flat screens. New Applications for PLC The maturity of PLC technologies convinced some manufacturers to use PLC as the transmission medium for applications that until then were not networked at all, or available only over proprietary and expensive networks.
122 Applications The industrial applications that currently use PLC networks are the following: • • • sensor networks; connection of programmable controllers; PC located in confined spaces where wiring is difficult (on top of a crane, in spaces with metal piping making it impossible to use Wi-Fi, and so forth).
Economic Perspectives 123 In Europe, the Valeo component manufacturer and the company manufacturing PLC products worked together to implement a solution using PLC to communicate the information from the vehicle sensors to the instrument panel. This type of PLC network can also be used to broadcast external camera or onboard DVD drive videos. Economic Perspectives As we have seen in this chapter, most applications transported by the electrical networks face multiple constraints inherent in PLC (i.e.
124 Applications Figure 6.
CHAPTER 7 Equipment Since the emergence of the HomePlug 1.0 specification in 2003, the PLC network equipment market has continued to grow. Originally focused on small networks with a low bit rate and few computers, it then turned to private individuals very keen on a technology enabling Internet connection sharing while eliminating wiring constraints and remaining relatively easy to use with the support of Internet access providers.
126 Equipment Table 7.1 PLC Technologies According to the Network Mode TECHNOLOGY MODE Ascom APA 450 (4.5 Mbit/s) Master-slave Itran (Main.net) PLTNet & ITM1 (2 Mbit/s) Master-slave HomePlug DS2 Spidcom 1.0 Peer-to-peer 1.0 Turbo Peer-to-peer AV Centralized DSS4200 (45 Mbit/s) Peer-to-peer 200 Mbit/s Master-slave 45 Mbit/s Peer-to-peer SPC200 (200 Mbit/s) Master-slave Master-Slave Mode Figure 7.
PLC Technologies 127 Figure 7.2 illustrates another architecture in the master-slave mode in a domestic electrical network. Here we find conventional private electrical network devices of which we had an overview in Chapter 2. The electrical switchboard controls electrical wirings, power outlets, bulbs, and electrical devices.
128 Equipment Table 7.
PLC Technologies Figure 7.3 129 Master device managing the ASCOM Powerline APM-45o PLC network Figure 7.4 ASCOM Powerline APA-45i slave device used for the connection of client terminals to the PLC local area network Figure 7.5 Slave device interfaces As illustrated in Figure 7.7, the peer-to-peer mode is ideal for local area networks since the LAN architecture must enable any terminal (typically PC) to exchange data with any other LAN terminal. HomePlug 1.0 and Turbo use this mode.
130 Equipment Figure 7.6 Details on the RJ-45, USB, and RJ-11 Ethernet LAN interfaces of the slave device Figure 7.7 Architecture of a PLC network in peer-to-peer mode In HomePlug AV PLC networks, one of the devices acts as the central device and manages the communications between the PLC stations of the network. The exchanges between PLC stations directly take place without going through the central device.
PLC Modems 131 Although the PLC technology does not use the modulation-demodulation process implemented in the modems, we talk about a PLC modem to designate the device to which the terminals that want to take part in the PLC network are connected. Unlike Wi-Fi interfaces, which are integrated into the terminals in the form of boards, the PLC interfaces are not integrated into the terminals.
132 Equipment ments and at temperatures that can be as high as 70°C and are made of plastic for consumer equipment and of metal for professional equipment. Inside the package, the entire hardware architecture is structured around the main component (HomePlug PLC chip, see Figure 7.8, middle). The Intellon manufacturer is the main supplier of HomePlug chips. Table 7.3 summarizes the various versions of chips that appeared as the HomePlug technology has progressed.
PLC Modems 133 Figure 7.9 Hardware architecture of a PLC modem Figure 7.10 Wallmount and desktop PLC modems Figure 7.11 illustrates a F@st Plug type Sagem USB PLC modem. PLC Ethernet Modems The generalization of network interface cards in computers, network terminals, and electronic devices, even in household appliances, simplifies the building of networks by using the Ethernet board’s RJ-45 connectors. This type of modem has become the most widely used PLC device.
134 Equipment Figure 7.11 F@st Plug type Sagem USB PLC modem Figure 7.12 Devolo Ethernet PLC modem of the dLAN Ethernet HighSpeed 85 type The increased performance of HomePlug PLC devices will probably lead the manufacturers to use 1,000baseT (1,000 Mbit/s) boards so that the throughput is not limited over the Ethernet interface. It would not be surprising to come across optical fiber PLC devices. The Devolo company offers devices with the two USB and Ethernet interfaces. Figure 7.
PLC Modems 135 Figure 7.13 Devolo PLC modem of the dLAN duo type with USB and Ethernet interfaces Figure 7.14 Devolo Homeplug AV PLC devices The networks of cable operators are much less widespread than the electrical network and generally have few TV sockets. However, such networks can end up complementing the electrical network due to their relatively constant speed, which in any case is more stable than that of the electrical network.
136 Equipment • • data circulation over the cable television network to make it the backbone of the PLC network; use of the coaxial interface with an adapter called “injector” (see later in this chapter) used to emit the PLC signal directly over the electrical wiring without using outlets.
PLC Modems 137 Figure 7.16 LEA-Legrand SmartPlug PLC outlet schematic diagram Figure 7.17 illustrates Thesys (on the left) and Devolo MicroLink dLAN Wireless (on the right) PLC/Wi-Fi modems. Some manufacturers are currently working on the optimization of the MAC layer between PLC and Wi-Fi in order to increase the reliability of these hybrid networks and their performance at the MAC layer level. These projects should result in products marketed in 2009.
138 Equipment Figure 7.17 • Thesys and Devolo PLC/Wi-Fi modems ADSL/router PLC modem used to transmit the signal originating from the Internet connection over the electrical network. Some devices even add a Wi-Fi board. Figure 7.18 illustrates Hub Netgear (on the left) and Thesys NetPlug (on the right) PLC modems. Figure 7.19 illustrates a Devolo dLAN ADSL modem router PLC device.
PLC Modems 139 Figure 7.19 Devolo ADSL/router PLC modem Figure 7.20 Devolo MicroLink dLAN Audio PLC modem nel) connectors used to broadcast four 192-Kbit/s audio channels over the electrical network. The audio PLC modems must be configured to parameterize the components of the PLC local area network and to load the plug-ins that the audio file servers require.
140 Equipment Figure 7.21 Wingoline telephone PLC modem with two RJ-11 telephone interfaces Methods for Accessing the Medium In PLC networks, the method for accessing the medium consists of connecting the PLC devices to the electrical network in order to obtain the best performance at the physical level and the best useful throughput at the upper layer level as a result.
Methods for Accessing the Medium 141 Coupling In the electrical field, coupling can be defined as how two electrical circuits connect together in order to generate an electron flow between these two circuits. This electron flow is conveyed by an electric and a magnetic field created between the two electrical circuits due to their inductive and capacitive nature. Inductive coupling is much more efficient than capacitive coupling.
142 Equipment Figure 7.24 illustrates the same principle but with two magnetic ferrites over a three-phase network. Choice of Injection Cable It is preferable to inject the signal over the neutral cable for a single-phase network and on one of the phases for a three-phase network. Better performance is achieved by injecting the signal over a single cable than over several cables at the same time.
Transformers and Meters 143 Direct Tap Methods The “direct tap” methods are used to connect PLC devices directly to the network electrical wirings by perforating the cable insulator and the electrical wiring itself. Such methods require resorting to an electrician authorized to intervene on LV (low voltage) or MV (medium voltage) electrical networks because of the electrical hazard. Figure 7.26 illustrates the operating principle of direct tap coupling.
144 Equipment • Some types of meters integrating a galvanic isolation also behave as PLC signal cutters. However, these models are relatively rare and most meters allow the PLC signal to pass. In both cases, it may be useful to override these devices to allow the PLC signal to extend over the entire electrical network.
145 Repeaters are major components of an electrical network for the PLC signal since they separate the public electrical network from the electrical network of a building, of an apartment, or of a company. Most meters allow the PLC signal to pass on each side of the electrical network. Therefore, it is important to correctly configure the PLC local area network encryption if the interception by a malevolent person of data flowing over the electrical network is to be avoided.
146 Equipment Figure 7.28 Example of PLC repeater use Home-Made PLC Repeater A home-made PLC repeater can be fabricated by using Ethernet PLC modems available in stores. All you have to do is to take two Ethernet PLC modems and connect them with an Ethernet cable (crossover or straight-through cable depending on whether the network interface cards are self-sense cards or not, i.e. that they can adapt or not to network cable crossover).
Filters 147 Figure 7.29 Home-made PLC repeater ticular, these electrical devices send back electromagnetic noises in the frequency band of the PLC devices. Therefore, it is interesting to install filters as close to the disturbing devices as possible in order to stop frequencies generating disturbances. A PLC filter can also be used to stop the outgoing PLC signal so that it does not propagate outside of the electrical network demarcated by the meter. Figure 7.
148 Equipment Table 7.5 Electrical Devices Disturbing a PLC Network ELECTRICAL DEVICE CAUSE OF DISTURBANCE Hairdryer Motor Cathode ray tube display Cathode ray tube Drilling machine Motor Light regulator Dimmer and Zener diodes Halogen lamp Dimmer and Zener diodes Power strip Defective electrical connections and accumulation of devices on the same outlet Device with incorrect CE marking Outside the disturbance templates Figure 7.
149 The Cost of PLC Figure 7.31 Eichhoff PLC blocking filter Figure 7.32 CMM antinoise PLC filter Figure 7.33 Lea NetSocket200+ The emergence at the beginning of 2006 of HomePlug Turbo products accentuated this fall. We can consider that the price of the HomePlug 1.0 products will still fall by another 20 to 50%.
150 Equipment As soon as the first HomePlug AV products appeared at the end of 2006, the price of HomePlug Turbo products felt in turn by 10 to 20%. For private individuals, PLCs are an ideal solution to share the same Internet connection between two PCs. Moreover, this is the most usual application of PLC devices.
CHAPTER 8 Installation The disturbances received and caused by PLC networks must be taken into account when installing the network. The electrical topology of the building or buildings where the devices will be installed is also a major element to be considered for building the architecture of the PLC network. Therefore, the definition of the electrical network topology is an essential step. It determines the PLC network data transmission performance.
152 Installation nologies are installed and implemented under the responsibility of MV electrical network operators. The 3- to 148-kHz and 1-to 30-MHz bands are called license-free bands, meaning that there is neither a need to ask for authorization nor a need to pay for a subscription in order to use them. However, they are subject to regulation by the ETSI (in Europe) and the FCC (in the USA) which lay down certain restrictions of their use in terms of transmission power.
Frequency Bands 153 Figure 8.1 Ethernet frame for the configuration of a HomePlug network Figure 8.2 PLC frequency bands As explained before, the PLC networks are not radio networks, but their implementation over electrical wiring produces radiated waves that propagate with the wiring acting as radio aerials. Therefore, PLC networks are viewed by the telecommunications regulatory bodies as radio networks that, as such, must comply with transmission power and frequency band constraints.
154 Installation broadcast digital quality radio programs over very long-range links and also to transfer data at rates of some tens of kilobits/s. The disturbances caused by PLC networks for amateur radio operators and the DRM have been the subject of many discussions to make it possible for various technologies to coexist. These discussions have led the developers of PLC technologies to include filtering techniques for frequencies already used by other radio technologies.
Frequency Bands Table 8.
156 Installation Figure 8.4 Architecture for Pulsadis signal implementation over the EDF LV electrical network ham radio operators are not used. The total HomePlug 1.0 bands are therefore equal to de 84 − 8 = 76. Table 8.2 summarizes the high rate frequency bands which can be used according to each type of PLC technology. Since the 1- to 30-MHz frequency band is divided into sub-bands, each subband conveys the OFDM modulation carriers at the transmission channel level.
Frequency Bands 157 In addition, and unlike Wi-Fi, the network configuration does not require you to make choices according to the other assigned channels. All the channels of the permitted bands, called “sub-bands” are used. Therefore, the network can be congested by the various technologies coexisting on the same electrical network. In this case, free or infrequently used sub-bands are used by PLC technology.
158 Installation Figure 8.6 shows that the transmission channel can be viewed as N sub-bands with their sub-carriers, all of them operating simultaneously and each conveying part of the physical layer data. Transmission Power of PLC Devices The measured power of the signal emitted by marketed PLC devices is usually 20 dBm (measured in the 1 to 30 MHz band).
Frequency Bands 159 Table 8.3 Gain/Power Correspondence GAIN (IN dBm) POWER (IN mW) 3 2 5 3.1 7 5 9 8 15 31.6 19 79.4 24 251.1 The HomePlug 1.0 technology includes 84 sub-bands of 195.31 kHz, whereas HomePlug AV comprises 918 narrower sub-bands of 24.414 kHz. Therefore, the PSD wave is less important in HomePlug AV, which makes it possible to increase the transmission power by 2.2 dB for PPDU data. Figure 8.7 illustrates the PSD deviation between HomePlug 1.0 and AV.
160 Installation Table 8.4 Transmission Power in Each Sub-Band PHYSICAL FRAME COMPONENT AVERAGE TRANSMISSION POWER HomePlug 1.0.1 HomePlug AV Preamble 3 dB 3 dB FC (Frame Control) 0 dB 3 dB PPDU data 0 dB 2.2 dB PRS (Priority Resolution Symbol) 3 dB 3 dB Figure 8.8 illustrates the HomePlug AV PSD curve in the 1- to 30-MHz band. We clearly observe that some frequencies are less emissive than other ones (–80 dB in comparison with −50 Hz).
Topology of Electrical Networks Table 8.5 161 PSD and Regulations in Each HomePlug AV Sub-Band CENTRAL SUB-BAND MAX. PSD FREQUENCY (MHz) (dBm/Hz) CARRIER ON/OFF COMMENT F ≤ 1.71 −87 Carriers 0–70 off AM broadcast band and below 1.71 < F < 1.8 −80 Carriers 71–73 off Between AM band and 160m amateur band 1.8 ≤ F ≤ 2 −80 Carriers 74–85 off 160m amateur band 2 < F < 3.5 −50 Carriers 86–139 on HomePlug carriers 3.5 ≤ F ≤ 4 −80 Carriers 140–167 off 80m amateur band 4 < F < 5.
162 Installation Ground 2 2 2 2 2 2 & Figure 8.9 Figure 8.
Topology of Electrical Networks 163 propagates over the cables then goes via the circuit breaker panel to start at the various cables again. The wiring length can exceed 300m, which is considered as the acceptable limit for a satisfactory useful throughput. The electrical devices connected to the network are potential sources of electromagnetic disturbances for the PLC signal. Remember that the average length of the electrical wiring between the switchboard and the farthest outlet should not exceed 200m.
164 Installation Like for single-phase networks, the average distance between the circuit breaker panel and the last outlet connected to the electrical wiring must not exceed 200m. If the PLC signal flows over the cables, goes through the circuit breaker panel, and propagates over other cables again, then distance is greater than 200m, and the useful throughput may fall.
Topology of Electrical Networks 165 electrical hazards. The protecting devices are called “circuit breakers” (or fuses for old networks). They may be of several types. Each circuit breaker has specific characteristics concerning the attenuation of the PLC signal conveyed over the cable. Figure 8.12 illustrates an example of a closed (on the left), open (in the middle), and front elevation (on the right) circuit breaker panel. The devices connected to the panel are identified in it.
Figure 8.
Topology of Electrical Networks 167 lets is 15m. The maximum cable length between the circuit breaker panel and the farthest point (luminous point or outlet) generally is 50m. It is important to limit the voltage drop in the electrical cables to 2% to keep an acceptable voltage for the electrical devices connected to the installation network.
168 Installation • Identify the areas of the electrical network where the PLC signal is not received and the parts of the building connected to other electrical networks or through various outlets revealing excessive cable lengths or subjected to too many disturbances. We’ll examine this topology choice again in Chapters 11 and 12. Propagation of the PLC Signal One of the recurrent problems with the PLC technology is the signal propagation over electrical wirings.
Interference 169 are therefore relatively insensitive to electromagnetic disturbances, or aerial cables, in which case they are more sensitive to electromagnetic disturbances but much less so than inside cables that are subject to disturbances close to those of various domestic devices. Table 8.8 summarizes the results obtained for various PLC technologies. Interference The interference notion is essential in PLC networks.
170 Installation Figure 8.14 network Electromagnetic disturbances caused by PLC devices connected to the electrical Figure 8.
Network Data Rates 171 Figure 8.16 illustrates how a power strip must be used with a PLC device. A power strip is inherently a source of noise for PLC devices to which the noise of disturbing devices connected to it must be added. In all cases, it is preferable to connect the PLC device directly to the wall outlet whenever possible or to connect it to a “biplite” (two outlet wall power strip).
172 Installation for data at these levels, which is calculated according to the overhead used for managing and sending the transmission. As we saw in Chapter 5, the data sent over this electrical interface corresponds to a physical frame, or PLCP-PDU. This frame consists of a PLCP header comprised of two fields and data originating from the MAC layer. As illustrated in Figure 8.17, each part of the PLCP-PDU is sent at different speeds. The PCLP-PDU header includes start and end delimiters.
Network Data Rates 173 Tt MAC = bytes × 8 bit byte 1534 , ≈ 0000876 . s 14 Mbit/s The 120-bit PLCP-PDU header is sent at a rate of 1 Mbit/s. Therefore, its transmission time (TtPLCP-PDU) is: Tt PLCP − PDU = 72 μs + 15 . μs + 72 μs ≈ 145.5 μs The total transmission time (Tt1) is therefore equivalent to: Tt 1 = Tt MAC + Tt PLCP − PDU ≈ 00010215 . s The useful throughput is equivalent to the volume of transmitted information, i.e., 1,500 bytes (12,000 bits) divided by the transmission time, i.e., 1.
174 Installation We are going to calculate the useful throughput associated with this ideal case (Du2). As in the example above, we consider the use of short preambles for 1,500-byte data transmitted at a speed of 14 Mbit/s. According to our preceding calculations, the data transmission time corresponds to Tt1, i.e.: Tt Data = bytes × 8 bit byte 1534 , + 145.5 μs ≈ 000167 . 0s 14 Mbit/s Since the duration of the ACK frame is 72 μs, its transmission time is equal to: Tt ACK = 72 μs + 145.
Network Data Rates 175 The transmission time (Tt3) becomes: Tt 3 + TWait + CIFS + TBackoff + Tt Data + RIFS + Tt ACK Since the waiting time and the back-off timer are not fixed, it is difficult to determine their values. However, we can consider that the sum of the waiting time and back-off time is generally equivalent to the transmission time in the ideal case. The back-off timer can be considered as zero compared with the waiting time.
176 Installation Table 8.9 Useful Throughputs of Local Area Networks THEORETICAL USEFUL DATA RATE THROUGHPUT NETWORK (Mbit/s) (Mbit/s) Ethernet 10 10 8.08 Ethernet 100 100 90.06 HomePlug 1.0 14 5.1 HomePlug Turbo 85 40 HomePlug AV 200 150 Iperf is used for generating any type of traffic between a client and a server. For our test, illustrated in Figure 8.
Network Data Rates 177 Table 8.10 shows the results obtained for various technologies with this test bed. Table 8.11 summarizes the necessary data rates for certain usual Internet applications (data, voice, or video applications). Data Rate Variation In a PLC network, the constraints related to the electrical interface can result in a variation of the data rate provided by the network.
178 Installation Figure 8.21 technology Theoretical data rate and useful throughput variation with the HomePlug 1.0 In the case of all the stations’ different speeds, the waiting time is prolonged. Because of this, the global network data rate falls heavily. If a station of the network transmits at a speed of 1 Mbit/s, its transmission time is 14 times higher than that of a station transmitting at 14 Mbit/s. Therefore, this station must wait 14 times longer before transmitting its data.
CHAPTER 9 Configuration The installation of a PLC network is rather simple. All you have to do is connect the PLC devices to an Ethernet network or to a modem (ADSL, cable, STN, and so forth) while taking into account the constraints mentioned in the previous chapter. The configuration of the network PLC devices and the terminal interfaces (generally PC network interface cards) connected to PLC devices follows the network installation.
180 Configuration configuring them according to the targeted operating systems. They are described for Windows XP as well as for the Linux and FreeBSD systems. Configuring a PLC Network Under Windows Almost all the tools used for configuring HomePlug PLC devices have the same functionalities for the configuration of HomePlug chip parameters. As we have seen in Chapter 7, HomePlug chips mainly originate from the Intellon manufacturer.
Configuring a HomePlug 1.0 or Turbo Network 181 Table 9.1 HomePlug Parameters Visible by Configuration Tools HomePlug PARAMETER INDICATIONS Bytes per 40 symbols Number of bytes per block with 40 OFDM symbols (used for calculating the estimated PHY data rate for HomePlug 1.0) Bytes per 336 us Block (for HomePlug Turbo) Number of bytes per 336-ìs block (used for calculating the estimated PHY data rate for HomePlug 1.
182 Configuration Table 9.2 Correspondence Between Indicated Physical Data Rate and Useful Throughput USEFUL PHYSICAL THROUGHPUT BIT RATE (Mbit/s) (Mbit/s) HomePlug 1.0 HomePlug Turbo Figure 9.1 • 14 4.5 to 5 12.83 3.5 11 3.2 10.16 2.9 8.36 2.4 6.35 2 4.04 1.22 3 0.89 1 0.33 0.9 (ROBO mode) 0.2 85 12.5 75 11.8 55 9.42 45 8.79 35 8.23 25 7 14 4.5 12.83 3.5 Encryption key configuration for HomePlug devices agement of the PLC network, Figure 9.
Configuring a HomePlug 1.0 or Turbo Network Figure 9.2 PowerPacket configuration utility from Intellon in main tab Figure 9.3 Configuration of priority levels for each VLAN in HomePlug 183 This tool provides the same functionalities as the previous tools but with an interface which is perhaps easier to use. Most PLC modems have Ethernet interfaces.
184 Configuration Once the tool is downloaded, we can proceed with the installation. Once the installation is completed, the Power Packet Utility program can be started (via Start, Programs). The program proposes several tabs corresponding to the various available functionalities as illustrated by Figure 9.4. To build a secure PLC local area network, it is necessary to start with the configuration of the NEK for the various devices to be connected to the network.
Configuring a HomePlug 1.0 or Turbo Network 185 In Figure 9.6, the NEK password has been replaced with the PLC Network value. The longer this password is, and the more numbers and symbols it has, the harder it is to crack for an intruder looking to access the PLC network. All the PLC devices connected to the electrical network can be configured from this configuration interface, whether these already exist in the PLC local area network or not.
186 Configuration Figure 9.8 illustrates the configuration of a PLC local area network using DEK read on the living room and bedroom devices connected to the same electrical network. Once all the network PLC devices are configured locally or using the DEK key, simply select the Products tab to check the status of the PLC links between the device to which the PC is connected and other PLC devices connected to the electrical network (see Figure 9.
Configuring a HomePlug AV Network Figure 9.9 187 PLC network status diagnostic function networks. It is possible to have several PLC local area networks on the same electrical network. These PLC local area networks just have to share the frequency band (from 1 to 30 MHz) and divide their transmission speed by the number of existing PLC local area networks.
188 Configuration Table 9.3 Various Chip and Firmware Versions for HomePlug AV Standard Functionalities 1.1 Advantages 1.0 Chips INT6000 INT6300 Firmware 1.x 3.
Configuring a HomePlug AV Network Figure 9.10 189 HomePlug AV PLC device association principle with the EasyConnect mode As a configuration example, we are going to use the tool developed by AsokaUSA for its easy implementation and its user-friendly user interface. Once the Power Manager tool is started, it offers a choice of network interfaces which will be used by the program as illustrated in Figure 9.11.
190 Configuration Figure 9.12 PLC tool module installation choice Figure 9.13 PLC tool installation progress assign a device name to it that will be used for easily retrieving the identity of this device in the PLC logical network supervision. At that level, the NEK used for all the PLC devices of the logical PLC network we want to configure can then be configured. Here, as illustrated in Figure 9.15, we use the HomePlug123 NEK.
Configuring a HomePlug 1.0 PLC Network Under Linux Figure 9.14 Renaming of local PLC device connected to the configuration PC Figure 9.15 NEK configuration for PLC logical network 191 With all the functionalities of the Power Manager tool, it is then possible to install, configure, and supervise a HomePlug AV network easily by following the installation rules previously stated in Chapters 7 and 8. Configuring a HomePlug 1.
192 Configuration Figure 9.16 Power Manager tool main tab Figure 9.17 Power Manager tool “Devices” tab http://download.devolo.biz/webcms/0607105001130251610/dLAN-linux-package-2.0.tar.gz Figure 9.19 illustrates the page of the Devolo site offering PLC configuration tools for dLAN duo devices. Just click on the Driver Linux link to download it, then save the file at a location on the disk when the downloading window illustrated in Figure 9.20 is displayed.
Configuring a HomePlug 1.0 PLC Network Under Linux Figure 9.18 DEK key configuration for a remote device Figure 9.19 Homepage for Devolo dLAN duo device configuration tools carcelle@debian:~/Projects/CPL$gunzip dLAN-linux-package-2.0.tar.gz carcelle@debian:~/Projects/CPL$gunzip dLAN-linux-package-2.0.tar.
194 Configuration Figure 9.20 Linux PLC tool downloading window The USB PLC device must then be connected to an available port of the PC and the device recognition must be verified by running the following command: carcelle@debian:~/Projects/CPL$dmesg The dmesg command gives the output illustrated in Figure 9.21. The directory in which the PLC tool was decompressed must be opened to install the driver downloaded in this way: carcelle@debian:~/Projects/CPL$cd dLAN-linux-package-2.0/driver/ Figure 9.
Configuring a HomePlug 1.0 PLC Network Under Linux Figure 9.22 195 Contents of USB PLC device driver directory To compile the USB driver, the next make usbdriver command must then be run (see Figure 9.24): carcelle@debian:~/Projects/CPL/dLAN-linux-package-2.0/driver$make usbdriver Once the compilation is completed, the next command, illustrated in Figure 9.25, is used for installing the driver at the suitable disk locations (see Figure 9.26): carcelle@debian:~/Projects/CPL/dLAN-linux-package-2.
196 Configuration Figure 9.24 Running the make usbdriver command Figure 9.25 Running the make install-usbdriver command carcelle@debian:~/Projects/CPL/dLAN-linux-package-2.0/driver$make installboot enables the USB driver to be loaded when starting up. Simply reboot the computer to validate all the commands. Once rebooting is completed, the device must still be connected to the USB port in order to make sure that the new USB Ethernet virtual board is installed as illustrated in Figure 9.27.
Configuring a HomePlug 1.0 PLC Network Under Linux Figure 9.26 Running the make install-boot command Figure 9.
198 Configuration debian:home/carcelle/Projects/CPL/dLAN-linux-package-2.0#./configure We can start by configuring the compilation parameters as illustrated in Figure 9.28. The compilation of the PLC configuration tool can be started using the make command as illustrated in Figure 9.29. Once the compilation has been completed, the compiled files must be installed in the correct disk locations using the make install command.
Configuring a HomePlug 1.0 PLC Network Under Linux Figure 9.29 Compiling the PLC configuration tool Figure 9.
200 Configuration Figure 9.31 • • • Sensing of an Ethernet PLC device using the Linux PLC configuration tool “set remote network password,” used for configuring the PLC network key on remote PLC devices connected to the electrical network (DEK); “list remote devices,” which is used for listing the PLC devices connected to the PLC network and configured with the same PLC network key; “exit,” used for exiting the configuration tool.
Configuring a HomePlug AV PLC Network Under Linux 201 after performing a check-out on the development repository using the following command: #svn co http://svn.open-plc.org/ • • • Installation of the Debian faifa.deb package from the debian.open-plc.org repository by adding this line in the /etc/apt/sources.list file: http://deb.open-plc.org Installation of the RedHat faifa.rpm package from the following link: http://rpm.open-plc.
202 Configuration option, he or she obtains the information on the firmware versions available on the Intellon chip as illustrated below: Choose the frame type (Ctrl-C to exit): 0xa000 Init: Frame: Get Device/SW Version Request Binary Data, 60 bytes 00000000: 00 B0 52 00 00 01 00 00 00 00000016: A0 00 B0 52 00 00 00 00 00 00000032: 00 00 00 00 00 00 00 00 00 00000048: 00 00 00 00 00 00 00 00 00 (0xA000) 00 00 00 00 00 00 00 00 00 88 E1 00 00 00 00 00 00 00 00 00 00 00 00 00 Dump: Frame: Get Device/SW
Configuring a HomePlug AV PLC Network Under Linux 00000000: 00000016: 00000032: 00000048: 00 A0 0C FF 00 00 B9 FF 00 B0 08 FF 00 52 47 FF 00 01 10 00 00 B0 03 00 00 F2 01 00 0C E6 00 00 203 B9 95 0C 00 08 66 B9 00 47 6B 08 00 0F 88 E1 00 39 03 0E 01 00 00 47 10 03 FF FF 00 Finally, the 0xA054 option is used for obtaining information on the PLC device manufacturer and a number of statistics on the PLC logical links between the network devices.
204 Configuration PB received failed..............: TBE errors over successfully....: TBE errors over failed..........: -- Rx interval 2 -Rx PHY rate.....................: PB received successfully........: PB received failed..............: TBE errors over successfully....: TBE errors over failed..........: -- Rx interval 3 -Rx PHY rate.....................: PB received successfully........: PB received failed..............: TBE errors over successfully....: TBE errors over failed..........
Configuring an HD-PLC Network 205 Powerline Bridge config version 0.2 by Manuel Kasper
206 Configuration • The Tasks Communications stack: Used with mails and events for tasks communication, interrupt handlers, and buffers for exchanging information with the hardware interface. Configuring a DS2 Network The Spanish manufacturer DS2 is a player on the HomePlug market whose products are not compatible with HomePlug devices. A DS2 200-Mbit/s PLC network is locally configured on the device via an HTTP interface. Therefore, it is identical for Windows and for Linux/FreeBSD.
Configuring a DS2 Network Figure 9.32 Addressing planes of a DS2 PLC network Figure 9.
208 Configuration Figure 9.34 DS2 PLC device configuration parameters Figure 9.
Configuring a DS2 Network 209 placed at 255.255.0.0. In this case, the default gateway is not important since the configuration PC has an address in the same addressing plane (10.10.1.10). Once these network parameters are configured, it is important to configure the network mode for each PLC device. As illustrated by Figure 9.36, the device closest to the circuit breaker panel is in master (HE) mode; the other devices are in slave (CPE) or repeater (TDREP) mode.
210 Configuration The priority of each of the network PLC devices can then be configured by setting the “Default priority” parameter of the “Priority configuration” section from 1 to 5 according to the network topology and the function of each device. For example, based on the topology of Figure 9.
Configuring Network Parameters Figure 9.38 211 Configuration of priority and security parameters for a DS2 PLC device Configuring Network Parameters To complete the configuration of a PLC network, it is still necessary to assign the correct network parameters to each device, including the configuration of the IP address, of the subnet mask, of the default gateway address, and of the DNS address.
212 Configuration There are two versions of the IP protocol: IPv4 and IPv6. The IPv4 address, which is most frequently used nowadays, is on 4 bytes and only limited functionalities are available, mainly centered on routing. IPv6 is an evolution of IPv4 which is scarcely implemented in networks. Its address is on 16 bytes, and it includes many functionalities, such as mobility, quality of service, and security management. Structure of an IPv4 Address The IPv4 address is on 4 bytes, i.e.
Configuring Network Parameters 213 0000000 and 0111111 in the binary format. Knowing that addresses 0.0.0.0. and 127.0.0.0 are reserved, there are therefore 27 – 2, i.e., 126 available class A network addresses, ranging from 1.0.0.0 to 126.0.0.0. The number of hosts is defined on 3 bytes (24 bits). Since the broadcast address (x.x.x.255) and address x.x.x.0 are reserved, this gives 224 – 2, i.e., 16,777,214 possible hosts per class A network address.
214 Configuration Subnet Mask The mask is used for knowing the network address of a computer via a binary subtraction between the mask and the computer IP address. If the IP address of a computer is 192.168.0.1 and if the 255.255.255.0 mask is applied to it, the binary subtraction of these two addresses gives 192.0.0.0, i.e., the network address. In general, the masks for class A, class B, and class C addresses are 255.0.0.0, 255.255.0.0, and 255.255.255.0, respectively.
Configuring Network Parameters 215 Configuring Network Parameters Under Windows XP In the Configuration panel, select “Network” then, in the network components area, choose the TCP/IP component of your Wi-Fi board and click on “Properties” to open the dialogue box.
216 Configuration the IAP like DNS addresses. If there are several DNS addresses, just add a line with nameserver adress_IP_DNS for each additional DNS address. This configuration can also be done semiautomatically by configuring the /etc/pcmcia/network.opts file in case the network interface card is a PCMCIA board or the /etc/network/interfaces file for a PCI or Mini-PCI board.
CHAPTER 10 PLC in the Home In spite of the still relatively high cost of PLC devices, more and more people are tempted to install a power line communication home network. The fact that no cables have to be laid seems to be the decisive factor for such a choice. The installation of a PLC network in a house or apartment is actually extremely simple. All you have to do is connect the PLC devices to the electrical network and configure them.
218 PLC in the Home Figure 10.1 PLC home network with shared Internet connection Figure 10.2 Sign symbolizing an electrical hazard The main electrical safety rules to be complied with are the following: • • • • • • Install a 500 mA differential circuit breaker for protection against short circuits. Protect outlets using a circuit breaker or a fuse not exceeding 16A. Do not expose the devices to sun or heat. Do not clean the devices using detergents or aerosols.
Choosing a PLC Technology • • • 219 Do not overload power strips or extension cords in order not to increase electrocution or fire risk. Comply with the operating instructions of the PLC devices. Do not try to install PLC injector systems on electrical wirings without the help of a competent electrician.
220 PLC in the Home offered by Internet access providers from anywhere in an installation, requires devices with a throughput around 200 Mbit/s at the physical layer level, which is the case of HomePlug AV devices. Insofar as all HomePlug devices are compatible between themselves for 1.0 and Turbo, various HomePlug products suited for the following uses will nonetheless coexist for some time. • • • HomePlug 1.
Placing Devices on the Electrical Network Figure 10.3 221 Regular wiring diagram for a domestic installation with Internet access Figure 10.4 illustrates the same home network with all the devices installed for the broadcasting of the various Internet flows to the outlets of the electrical network. The PLC device located on outlet 3 is used by the computer for connecting to the Internet via the outlets (outlet 3 to outlet 1).
222 PLC in the Home Figure 10.4 Place of PLC devices in the domestic installation available for the IP network applications based on the PLC network. According to this table, it is important to find an outlet 5 that gives a minimum 10-Mbit/s displayed throughput. The analog telephony flow originating from the Internet connection and available on the RJ-11 connector of the InternetBox connected to the telephone jack can also be broadcast over the electrical network.
Configuring Security Parameters 223 Table 10.2 Displayed and Useful HomePlug Turbo PLC Throughputs DISPLAYED THROUGHPUT (Mbit/s) USEFUL THROUGHPUT (Mbit/s) 85 12.5 75 11.8 55 9.42 45 8.79 35 8.23 25 7 14 4.5 12.83 3.5 11 3.2 10.16 2.9 8.36 2.4 6.35 2 4.04 1.22 3 0.89 1 0.33 0.9 (ROBO mode) 0.2 The following Niroda devices of the RJ-11 PLC network can be placed as indicated in Figure 10.
224 PLC in the Home Figure 10.5 Various PLC networks connected to an InternetBox coverage area that can extend beyond the home area. This allows anybody to access the network and to use its Internet connection, for example. PLC networks provide security mechanisms likely to prevent eavesdropping with a suitable password management scheme. To protect the network in a still more reliable way, there are other firewall-based solutions (authentication server and virtual private network).
Configuring Security Parameters Figure 10.6 225 Place of devices used for broadcasting IP telephony over the electrical home network Figure 10.8 illustrates the location of these various gateway types in a domestic installation. For a HomePlug device, the PLC gateway requires no specific configuration compared to the other PLC devices of the network since HomePlug Turbo operates in peer-to-peer mode.
226 PLC in the Home Figure 10.7 Broadcasting of the analog telephone signal over the electrical home network Figure 10.
Configuring Security Parameters 227 Table 10.3 Data Traffic Priority Levels for the PLC Gateway PRIORITY FOR DATA TRAFFIC HomePlug 1.0 AND TURBO PRIORITY 0 CA0 Low priority 1 2 CA1 3 4 CA2 High priority 5 6 CA3 7 (highest priority level) Figure 10.9 Launching the PLC priority configuration tool The WinPCap tool used for managing inputs/outputs on the network interface card must be installed beforehand. This tool is generally pre-installed by the PLC configuration tools.
228 PLC in the Home Figure 10.10 Configuring the Ethernet board connected to the PLC device Once the network interface card has been chosen, the DOS window closes; this indicates that the priority configuration is completed. It is important to identify the PLC device with the highest priority level and to maintain its connection to the Internet gateway or to the InternetBox.
Configuring Security Parameters Figure 10.11 229 “Products” tab of the AsokaUSA PLC configuration tool This key must have between 4 and 24 characters and include numerals and (lowercase and uppercase) letters if possible, for example, PLCNetworks. Just click on “Update” for local device configuration. The configuration is confirmed thanks to a window indicating “Network Encryption is successfully changed” as illustrated in Figure 10.12.
230 PLC in the Home Figure 10.13 • • Testing good operation of the PLC network at the IP level MAC device = 00:0C:B9:08:47:0F to living room device: “good” quality with 24.55 Mbit/s displayed throughput; MAC device = 00:0C:B9:08:47:10 to bedroom device (HomePlug 1.0): “first-rate” quality with 13.43 Mbit/s displayed throughput. Since the PLC network security is confirmed, the security of the terminals themselves can be configured. Maximum Number of PLC Devices on the Same Network The HomePlug 1.
Configuring Security Parameters 231 To test the good operation of the PLC network, it can also be useful to run “Ping” commands from the PC connected to the PLC network to the InternetBox as illustrated in Figure 10.13. For this purpose, all the PCs or terminals must be in the same addressing plane as the InternetBox (for example, for an IP network of the 192.168.10.x type, the InternetBox is in IP = 192.168.10.1 and the other devices in IP = 192.168.10.100, 101, 102, and so forth).
232 PLC in the Home Figure 10.14 Windows XP network connection window Hardware firewalls must be installed on the computer connected to the Internet. This is ideally a dedicated computer, such as the access gateway defined above (see Figure 10.17). VPN and PPPoE The only way of guaranteeing the total security of a PLC network consists of using a VPN (virtual private network) as explained in Chapter 4.
Configuring Security Parameters Figure 10.15 Ethernet properties dialogue box Figure 10.16 Advanced connection firewall configuration parameters 233 Another way of improving the security of the PLC network and of the IP local area network consists of installing a PPPoE server and an associated RADIUS server.
234 PLC in the Home Figure 10.17 PLC network with access gateway protected by a firewall Figure 10.
Configuring an Internet Gateway Figure 10.19 235 PLC network with gateway protected by PPPoE and RADIUS servers This protection technique based on PPPoE tunnels is widely used by Internet access providers to ensure the separation between the various Internet access clients but it can be applied to a PLC home or professional network as well. Configuring an Internet Gateway In a PLC network, any Internet connection may be used: 56K modem, ISDN, cable, ADSL, ADSL2+, satellite, or FTTH (fiber to the home).
236 PLC in the Home Figure 10.20 Internet connection via a dedicated computer The disadvantage of this type of typology is that the PLC device only rarely has a firewall used for blocking various traffic types and avoiding attacks on the network or a VPN. In a topology where a dedicated computer is used for the Internet connection, any firewalling software or VPN server can be installed to protect the network.
Configuring an Internet Gateway Figure 10.21 237 Internet connection via a PLC modem-router offers a user-friendly station configuration mode, but this configuration can also be performed manually by modifying the board parameters directly. DNS Addresses The DNS addresses are given by the Internet access provider, except if there is a local DNS in the home network. As far as IP addresses are concerned, all the network stations must have the same network address, e.g., 192.168.0.x or 10.0.x.
238 PLC in the Home Figure 10.22 Configuring home network IP addresses In the case where NAT and DHCP functionalities are not built into the Internet modem or the InternetBox used as an Internet access gateway, it is still possible to use them, but by configuring a dedicated computer acting as a gateway, as illustrated in Figure 10.24.
Configuring an Internet Gateway Figure 10.23 239 Ideal architecture of a PLC home network DHCP can provide a station with a certain range of addresses and that each of these addresses is negotiated and is valid only for a given period of time. DHCP Architecture The DHCP is based on a client-server architecture. In the case of PLC networks, the DHCP client is the device connected to the PLC network and the DHCP server is the PLC modem-router. In the example illustrated in Figure 10.
240 PLC in the Home Figure 10.24 Internet Architecture of a PLC home network with a dedicated gateway for accessing the Figure 10.
Configuring an Internet Gateway 241 Once these parameters have been received, the computer can dialogue freely with other computers on the network or have access to the Internet if there is a connection sharing scheme. This is a user-transparent mechanism that does not take more than one second. Another characteristic feature of DHCP is the lease. As we explained above, the parameters given to a network station are valid for a given period of time only.
242 PLC in the Home Configuration Under Windows XP Configuring a DHCP client under Windows XP is very simple: • • • • • • When inserting an Ethernet board under Windows, it is automatically configured as the DHCP client by default. If the board has already been configured before with a fixed IP address, open the Configuration panel and select “Network connection.” The window illustrated in Figure 10.27 is displayed.
Configuring an Internet Gateway Figure 10.28 Status of the connection to the local area network Figure 10.29 Properties of the connection to the local area network Figure 10.
244 PLC in the Home Figure 10.31 TCP/IP parameters of the local area network Ethernet board The board configuration can be checked via the ipconfig command: • • In the Start menu, click on the “Execute” button, and enter cmd to open the MS-DOS command. When prompted to, enter ipconfig/all to display all the information concerning the network interface card and make sure that it has actually been configured. In Figure 10.33, we can see that the information is the same as that obtained previously.
Configuring an Internet Gateway Figure 10.
CHAPTER 11 PLC for Businesses The PLC networks increasingly invade the business world, and more generally the networks of professional and industrial buildings, where they complete or replace Wi-Fi or Ethernet networks.
248 PLC for Businesses Network Architecture In a company, there can be great differences in the architecture of a PLC network according to the network size, to the number of stations to be connected, and to the objectives assigned to the network. The network architecture of a small company with a small number of PCs (less than ten stations) and an Internet connection via a cable modem or ADSL does not differ from the architecture of a home network.
Network Architecture Figure 11.
250 PLC for Businesses The PLC technologies operate at the data link layer level (MAC layer); they cannot be used for the direct remote SNMP interrogation. However, a number of hardware and software tools are used for supervising all the PLC networks. Figure 11.3 illustrates the supervision of several PLC networks from various technologies. AsokaUSA, DS2, and Spidcom directly implement a HTTP interface and an SNMP stack (with the corresponding MIB) in their devices. Since the HomePlug (1.
Choosing Network and Electrical Equipment Table 11.1 251 Criteria for the Choice of Corporate PLC Technologies PLC TECHNOLOGY HomePlug CHOICE CRITERION 1.0, Turbo Low cost, ideal for SMB, few advanced functionalities, DES 56-bit security, easy deployment, few administration possibilities AV Leading-edge technology, high useful throughput, higher cost, advanced network management functionalities, guaranteed QoS AsokaUSA HomePlug 1.
252 PLC for Businesses • Integration of advanced network functions (NAT router, DHCP server, firewall, switch, Wi-Fi, and so forth). As far as the PLC devices are concerned (filters, coupling systems, PLC signal injectors, and so forth), it is recommended to use professional products and to install them with the help of accredited electricians in order to ensure compliance with the security standards and to obtain a perennial installation.
Choosing Network and Electrical Equipment 253 (guaranteed high thrughput, propagation time, jitter) are crucial for the good transmission operation without data loss.
254 PLC for Businesses Table 11.3 Main HomePlug AV QoS QMP QMP PARAMETER DESCRIPTION Delay bound Maximum time measured in microseconds to convey an MSDU between the moment when it is delivered to the SAP (service access point) convergence sub-layer at the sending station data link layer level and the moment when it is received at the receiver station SAP layer level.
Choosing Network and Electrical Equipment 255 Table 11.
256 PLC for Businesses Figure 11.5 Inductive coupling methods for PLC devices over electrical wirings cast the Ethernet (Internet or LAN) frames to the various PLC devices connected to the outlets. It is important to recover a wiring diagram of the building in order to know the topology of the electrical network and to see the various phase distributions (in the case of a three-phase topology).
Security Parameters Figure 11.6 257 PLC signal injection at the circuit breaker panel of a building cal network outlets. This central location can be in the technical room as close to the LAN Ethernet network devices as possible. In the case of a centralized mode architecture (HomePlug AV), the architecture devices are the CCo (central coordinator) and the STA (stations). There is only one CCo per AVLN (AV logical network) to manage the PLC links between the network PLC devices.
258 PLC for Businesses In the case of a company, it is however necessary to see to it that the firewalls for access to the Internet are correctly configured and that the various logical corporate networks are correctly separated in order to protect its data. The following sections introduce the main lines to be complied with for this purpose.
Security Parameters Figure 11.8 firewall 259 Architecture of a PLC network connected to the corporate network by means of a as a gateway capable of managing all these network keys. The 8950 switch from AsokaUSA does this by being capable of managing up to 253 PLC network keys and 1,024 users at the same time. Information on this product is available at the following address: http://www.asokausa.com/products/commercial/pluglan_8950.
260 PLC for Businesses According to the manufacturers of PLC devices and to the PLC technologies, it is more or less possible to configure advanced security functionalities. Table 11.5 summarizes the main security functionalities of the various PLC technologies. VLAN (Virtual LAN) As its name indicates, a VLAN (virtual LAN) is used for defining virtual local area networks. This technology, which has appeared for several years in Ethernet networks under the IEEE 802.
Installing and Configuring a PLC Repeater (Bridge) 261 network. To remedy this attenuation problem and obtain an optimum and complete PLC signal coverage for a building, it may be useful to install devices called “repeaters” in order to extend the PLC network to the areas of the electrical network where the PLC signal attenuation is too high. This section gives a configuration example for a repeater device used for extending the installed PLC network.
262 PLC for Businesses Figure 11.10 Logical representation of PLC repetition on two segments To enable active PLC devices from Oxance to behave as a repeater (or bridge), an option must be activated by connecting to the PLT320 via the interface available on the PLT300 and by entering the MAC address of the PLT320 in the Source menu of the Oxance menu bar. A drop-down list displays the identified devices.
Sample Implementation of PLC in a Hotel Figure 11.11 263 Infrastructure of IP telephony over PLC network Sample Implementation of PLC in a Hotel A hotel wants to be fitted with a multi-purpose computer network for the various services it proposes to its customers and decides to install a PLC network. Figure 11.12 illustrates the hotel network architecture with two buildings supplied by a meter and two circuit breaker panels (one for each building).
264 PLC for Businesses Figure 11.12 Hotel PLC network architecture The following elements must be taken into account in the network architecture, as illustrated in Figure 11.13: • • • • Place and configuration of the various PLC gateways and PLC signal injection; Hotel Internet access; Network keys of the various PLC networks, whether separated or not; Network links between the buildings. Figure 11.14 illustrates the overall logical architecture to be implemented.
Figure 11.
266 PLC for Businesses Figure 11.14 Overall logical architecture of the hotel PLC networks Hotel Story PLC Networks The hotel proposes to the customers to connect to the Internet in their bedrooms via a lent PLC device to be connected to the bedroom outlets. This connection to the Internet must take place in an authenticated, secured, and confidential manner. The PLC devices available at the hotel reception are, therefore, preconfigured so that they can connect to the PLC story network.
Sample Implementation of PLC in a Hotel Figure 11.15 267 Managing the story PLC network with more than 15 devices devices. For 22 bedrooms, it is just necessary to have two segments (one with 15 and one with 7) to cover the story requirements. Figure 11.16 illustrates the PLC architecture to be configured for the AsokaUSA 8950 PLC device used for managing these 3 segments with 15 PLC devices. Internet Access with Confidentiality Between Computers One of the disadvantages of the PLC HomePlug 1.
268 PLC for Businesses Figure 11.16 Story network architecture with several PLC segments Configuring a DHCP Client Under Linux Finding Linux systems in corporate networks, whether on servers or client stations, is more and more frequent. Therefore, it is important for the administrators of professional networks to know how to configure a DHCP client under Linux. Before starting the configuration of the DHCP client, it should be ensured that the Ethernet board runs under Linux.
Configuring a DHCP Client Under Linux Figure 11.17 269 Internet access with confidentiality between computers Configuring a DHCP/NAT Server Most Linux distributions propose a DHCP server called dhcpd. The configuration of the DHCP server just requires the creation of a dhcpd.conf configuration file which will be placed in the directory. Here is an example of dhcpd.conf file: subnet 10.0.0.0 netmask 255.255.255.0 { range 10.0.0.2 10.0.0.50; option routers 10.0.0.1; option domain-name-servers 10.0.0.
270 PLC for Businesses It can also be started automatically by creating a script in the /etc/rc directory and by incorporating the following command: /usr/sbin/dhcpd eth0 NAT (Network Address Translation) NAT is a technique used for connecting several computers to the Internet on the same IP address. NAT has been and still is widely used for compensating for the small number of available IP addresses.
Configuring a DHCP Client Under Linux 271 ally after having switched on the gateway, or to write a script in the /etc/rc directory in order to automatize the NAT execution when starting the gateway. Irrespective of the kernel used, the /etc/network/options file must first be modified using the vi command, for example, and modifying the ip_forward=no line to ip_forward=yes. For the 2.2 kernels, the ipchains command is used for managing the NAT: /sbin/ipchains –A forward –i ppp0 –s 10.0.0.
CHAPTER 12 PLC for Communities During the last years, high throughput Internet accesses proposed by Internet access providers have spectacularly developed, providing both higher throughputs and new media to reach an increasing number of customers (telephone cable, TV cable, radio, and so forth).
274 PLC for Communities Figure 12.1 Architecture of electrical subnets The various subnets of the electrical network partly differ by the network owner, on the one hand (cables, pylons, infrastructure devices, and so forth), which is in general the community for HTA electrical networks, and by the network operator, on the other hand, i.e. the one that uses, supplies, services, and maintains the network and the infrastructure devices forming it, generally an electrical utility for LV electrical networks.
Electrical Networks for Communities 275 the framework of an electrical network that has safety rules different from those of twisted pair, cable TV, or optical fiber networks. For electrical utilities managing the local electrical networks (village communities, small towns, built-up areas, commune syndicates, and so forth), the PLC can represent the best technology to connect the local authorities located in white areas to the Internet.
276 PLC for Communities • • • • Network topology; Distance between pylons; Distance between the transformer and the various meters that it supplies; Number of meters behind a MV/LV distribution transformer. For each of these networks, three MV electrical network topologies are possible: star, ring, or mesh topologies. The most widespread topology is the mesh topology, which has the advantage of protecting the entire electrical network against possible electrical defects at some points of the network.
Implementation of a Communitywide PLC Network Figure 12.5 Ring topology Figure 12.6 Mesh topology 277 The electrical network construction rules determine the PLC engineering to be implemented to obtain the best coverage and the best performance of the IP network to the subscribers and the outlets of the community buildings. Figure 12.
278 PLC for Communities Figure 12.7 Example of a power line distribution system for a community and the PLC infrastructure in collaboration with the operational teams of the local electrical utility. The prime contractor team consists of electrical engineers for compliance with the safety rules and of telecom/network engineers for the use of the electrical infrastructure and the implementation of Internet services satisfying the residents’ requirements.
Implementation of a Communitywide PLC Network Figure 12.8 279 Topology and electrical devices in a building dense urban area • • Distribution networks. Used for connecting the exchanges of the Internet access providers and the subscribers to the Internet and to IP networks in general. These networks consists of all the media that can be used to reach the subscribers located at a few kilometers of the Internet access providers’ exchanges.
280 PLC for Communities POP = Point of Presence (very high throughput IP point of presence) Figure 12.9 Telecommunications networks pyramid Constraints of the Electrical Network for PLC Architecture If the electrical network of a country supposedly not interconnected to its neighbors is examined, the main constraints influencing the architecture of a PLC network in a low voltage electrical network are the following: • • • • Geographical area.
Implementation of a Communitywide PLC Network 281 tecture that we have seen in Chapters 10 and 11 dedicated to home and corporate PLC networks. The topology of the low voltage HTA electrical network of the community from the MV/LV transformer to the various building meters is a star topology.
282 PLC for Communities Figure 12.11 • • • • Example of connection for Eichhoff PLC injector PLC gateway used for the connection to other IP networks. PLC injectors used in the public electrical network installations as illustrated in Figure 12.11. PLC repeaters used for providing a continuous PLC signal over the entire cable length up to the subscriber, which can reach 200 to 300m.
Implementation of a Communitywide PLC Network • 283 Intervention on PLC devices by authorized people. The authorizations for interventions on an electrical network (deenergized, close or energized) are obtained via specific trainings and approvals by ad hoc bodies. Table 12.1 lists the various authorizations for the various classes of technical parties intervening on an electrical network according to the work to be carried out.
284 PLC for Communities Table 12.
Implementation of a Communitywide PLC Network Figure 12.12 285 PLC distribution network supervision architecture All the infrastructure devices can be supervised with the SNMP or TR-069 protocols using tools used for retrieving information (throughputs, status of the interfaces, temperatures, binary error rate, and so forth) and to trigger threshold alarms. The HP OpenView tool, for example, is used for centralizing the fed back SNMP data.
286 PLC for Communities Figure 12.13 • • PLC distribution network architecture example PLC distribution network, with the master PLC gateway or gateways at the electrical substation (hosting the MV/LV transformer, the repeaters and the slave PLC devices (CPE)). The slave devices connect to the master device and are accessible via their IP addresses, which are in a private IP addressing plane different from that of public IP addresses delivered to the community subscribers.
Implementation of a Communitywide PLC Network 287 Table 12.
288 PLC for Communities Figure 12.14 PLC device configuration architecture for GPS positioning of the distribution network devices (France), with the support of the Tiscali Internet access provider for the Internet connection. This distribution network was intended to test the quality of an Internet access over the EDF low voltage distribution network in a dense urban environment (star electrical network topology of the tree type).
Implementation of a Communitywide PLC Network 289 The deployment of PLC distribution networks has enabled the introduction of high throughput in “white” areas not served by ADSL offers. So, these two communes could have access to high throughput Internet from a point of presence close to the communes via a complete PLC architecture.
290 PLC for Communities Table 12.4 Examples of Large-Scale PLC Networks Deployments Worldwide DEPLOYMENT DEPLOYMENT PLC OPERATORS COMMENTS AREAS COUNTRY America Europe Africa Asia United States Amperion Cap Girardeau, MO United States Current Technologies HomePlug 1.
Implementation of a Communitywide PLC Network Figure 12.15 APPC PLC deployment architecture (Source CIGRE) Figure 12.16 Example of capacitive coupling in air insulated MV cells (Source CIGRE) 291 Current Technologies has developed a repeater-amplifier product at the level of the physical layer that is used for reamplifying the PLC signal over the MV and LV lines without losing the bandwidth, like in the case of PLC repeaters operating on the MAC layer.
292 PLC for Communities Figure 12.17 Example of capacitive coupling in gas insulated MV cells (Source CIGRE) Figure 12.18 Installation of a Current PLC gateway on a pylon (source Michel Goldberg) Current proposes a system for collecting meter information over the MV and LV network. This information relates to the various electrical parameters available on the network (kVA, kWh, leakage currents, and so forth) via an HTTPS centralized interface at the disposal of the utilities.
Implementation of a Communitywide PLC Network 293 The interface can be operated with the GIS (Geographical Information Systems) of the utility. Therefore, the data of a transformer or meter can be displayed from the map of the area in question via this interface. The interface is also used for displaying defects on the electrical network according to the alarms fed back by the meters and the measuring instruments.
CHAPTER 13 Hybrid PLC The recent developments of computer communication media have multiplied the network media (wired Ethernet, Wi-Fi, PLC, optical fiber, cable TV, and so forth) providing the suitable throughputs, coverage, and transit time to new generation applications. Since none of these media offers by itself the ideal capacities, hybrid networks appeared in order to make the best use of these technologies.
296 Hybrid PLC PLC Technologies Between Themselves As we have seen throughout this book, there is no IEEE PLC standard as yet. As a result, a number of PLC technologies coexist on the public and private electrical networks. Figure 13.
Coexistence of Multiple Networks 297 • Management of hybrid accesses between FDMA (frequency division multiple access) and TDMA (time division multiple access); • Management of the QoS by a TDMA time space system, like in HomePlug AV for HD video applications. As illustrated by Figure 13.2, these two principles should make it possible to avoid mutual interference and optimize the use of the common communication medium.
298 Hybrid PLC Figure 13.3 cation Management of coexisting HomePlug PLC networks with the HomePlug AV specifi- Table 13.1 Interoperability Between PLC Technologies PLC TECHNOLOGY A PLC TECHNOLOGY B HomePlug 1.0, Turbo AV Oxance BPL DS2 Spidcom CC HomePlug 1.
Coexistence of Multiple Networks Figure 13.4 299 PLC/Wi-Fi hybrid architecture example The NBG318S devices from Zyxel, illustrated in Figure 13.5, will be used to illustrate the configuration of such an architecture. Zyxel proposes a router including a device fitted with an Ethernet PLC interface and a Wi-Fi interface with an outlet and an aerial for the IEEE 802.11 interface. The configuration of this hybrid network requires access to the Wi-Fi device parameters.
300 Hybrid PLC Figure 13.5 Configuration of PLC/Wi-Fi devices Figure 13.6 Connection to the PLC device used as a Wi-Fi access point The next configuration step concerns the parameters specific to the Wi-Fi network and to its security. First, an SSID (i.e., a Wi-Fi network name) must be chosen so that the clients wanting to connect recognize it. PLC Networks is chosen here as illustrated in Figure 13.7. A channel (from 1 to 13) can then be selected in the 2.4-GHz band.
Coexistence of Multiple Networks Figure 13.7 301 Configuring the Wi-Fi access point properties Choosing the IEEE 802.11 Mode When the network is configured in the “802.11 Super G dynamic” mode, it is important to make sure that all the 802.11 clients connecting to the network support this mode. If this is not the case, choosing the 802.11b or 802.11g modes supported by most current Wi-Fi terminals is preferable. Once the 802.
302 Hybrid PLC Figure 13.8 Configuring the parameters of the HomePlug AV PLC network The network PLC devices must also be named in order to have a better readability of the network with respect to the MAC addresses of each device. In this case, the default name of the associated device is Example 1. Figure 13.8 shows the association of a new device and Figure 13.9 indicates the result of this association when the HTML page is refreshed.
Coexistence of Multiple Networks Figure 13.9 Figure 13.
304 Hybrid PLC Coexistence of PLC and Wired Ethernet The coexistence of PLC and wired networks (Ethernet cable, optical fiber, cable TV, telephone cable, and so forth) does not generate disturbances since all the frequency bands used by these technologies are outside of the PLC frequency bands. Only the VDSL distribution technology, which will allow reaching throughputs of several tens or so of megabits per second over copper telephone cables, will use the 138-kHz to 12-MHz frequency band.
Optimizing Network Architectures 305 Table 13.2 Comparison Between the Various Network Technologies NETWORK COST DISADVANTAGES ADVANTAGES TECHNOLOGY Ethernet cable (CAT5 100baseT) High Wi-Fi (IEEE 802.
306 Hybrid PLC • • • Open-endedness, removal requirements, temporary networks, test networks, and so forth; User groups and requirements of specific logical networks; Easy network deployment, configuration, and global supervision. It is essential to specify these characteristics to build a network architecture that is both efficient and stable in time.
Optimizing Network Architectures Figure 13.
308 Hybrid PLC Figure 13.13 Optimized PLC/Wi-Fi devices HomePlug AV and IEEE 802.11 Super G dynamic to market in order to provide better throughputs and the broadcasting of HD video streams. Figure 13.13 illustrates the exchange of frames between a PLC device and a Wi-Fi device with an example of a PLC/Wi-Fi hybrid device below.
Resources Web Sites Standardizations Organizations IEEE: http://www.ieee.org http:// grouper.ieee.org/groups/1901/ for the PLC network working group ETSI: http://www.etsi.org IETF: http://www.ietf.org Cenélec: http://www.cenelec.org IEC and, namely, CISPR: http://www.iec.ch/cgi-bin/procgi.pl/www/iecwww. p?wwwlang=e&wwwprog=dirdet.p&progdb=db1&committee=CI&css_color=pu rple&number=CIS/I PLC Technologies HomePlug: http://www.homeplug.org DS2: http://www.ds2.es Spidcom: http://www.spidcom.
310 Resources http://www.atlantisland.it/ http://bewan.com http://www.billion-france.com/ http://cometlabs.com/ http://www.courantmultimedia.fr http://www.connectland.net/ http://www.corinex.com http://www.defidev.com/ http://www.devolo.com http://www.dynamode.co.uk/ http://www.edimax.com/ http://eichhoff.de http://www.gigafast.com http://www.ilevo.com http://www.jaht.com/ http://www.leacom.fr http://www.linksys.com http://www.Main.net-plc.com/ http://global.mitsubishielectric.com/bu/plc/ http://www.
Books and Articles 311 Low Bit Rate PLC Technologies http://www.siconnect.com http://www.itrancomm.com http://www.arianecontrols.com Books and Articles DOSTERT (KLAUS), Powerline Communications, Prentice Hall, 2000 LEE (M. K.), NEWMAN (R. E.), LATCHMAN (H. A.), KATAR (S.), YONGE (L.), HomePlug 1.0 Powerline Communication LANs––Protocol Description and Performance Results, version 5.4, 2000, Wiley. PAVLIDOU (F.-N.), LATCHMAN (H. A.), HAN VINCK (A. J.), NEWMAN (R. E.
About the Author Xavier Carcelle earned an M.Sc. in EE from Ecole Normale Supérieure, France. He has held different positions in the industries of energy and telecommunications in France and in the United States. He worked for 6 years at Electricité de France, the largest electrical utility worldwide, as a telecommunications expert for PLC and wireless networks. In the United States, he worked as a software engineer on video compression algorithms for IP networks.
Index A ACK response, 46, 47 Active repeaters, 145 Address classes, 212–213 AES (Advanced Encryption Standard), 65–66 AIFS (allocation interframe spacing), 41 Analogy with network hub, 25, 26 Antinoise filters, 147, 149 Applications, 107–124 audio broadcasting, 118 economic perspectives, 123–124 file sharing, 116–117 in industry, 121 InternetBox, 119–121 Internet connection sharing, 116 in motor vehicles, 122–123 multimedia, 114–115 over coaxial cable, 122 printer sharing, 116–117 in public spaces, 122 recr
316 Broadcast address, 102 Brute force attacks, 72 Business PLC, 247–271 access to electrical medium, 253–255 application classes, 255 architecture illustration, 249 capacitive coupling, 253 DHCP client configuration, 268–271 DHCP/NAT server configuration, 269–270 equipment placement, 255–256 equipment selection, 251–256 hotel implementation, 263–268 inductive coupling, 253 NAT (network address translation), 270–271 network architecture, 248–250 network architecture selection, 256–257 network selection, 25
Index HomePlug AV network, 187–191 HomePlug AV network under Linux, 200–204 HomePlug Turbo network, 179–187 Internet gateway, 235–245 network parameters, 211–216 network parameters (Linux/BSD), 215–216 network parameters (Windows XP), 215 PLC gateway, 224–228 PLC network under FreeBSD, 204–205 PLC security, 228–230, 259–260 repeater, 261–262 Consortium standards, 5 Contention-free access (CFA), 53 Counterattacks, 61 Coupling, 140–141 capacitive, 140 direct tap, 143 inductive, 141 between phases, 21 Cryptog
318 EAP (extensible authentication protocol) (continued) EAP-MD5, 81 EAP-TLS, 81–82, 82 LEAP, 82 PEAP, 82 EAPoL (EAP over LAN), 82–83 EIFS (extended interface spacing), 41 Electrical networks architecture, 15–24 attenuation on, 165–167 circuit breaker panel, 164–165 for communities, 273–277 distribution, simplified architecture, 17 electrical wiring, 17–22 interference effects, 169–171 issues in, 282–283 modeling, 22–24 MV (medium voltage), 151 operational responsibilities, 17 placing devices on, 220–223 s
Index electromagnetic compatibility and, 157–160 high bit rate, 155–157 illustrated, 153 low bit rate, 154–155 MV networks, 151 OFDM, 91 radio frequency regulation, 152–157 use for HomePlug AV devices, 93–94 Frequency response, 21 Functionalities, 31–60 dynamic adaptation of bit rate, 58 frame level, 54–57 network mode, 31–38 service quality, 59–60 transmission channel, 38–54 unicast, broadcast, multicast, 58–59 G Gain/power correspondence, 159 Government standards, 5–6 GPS position, 286–287 Ground, 165
320 HomePlug 1.
Index DHCP client configuration, 268–271 HomePlug 1.
322 Network parameters address classes, 212–213 configuration, 211–216 configuration (Linux/BSD), 215–216 configuration (Windows XP), 215 DNS (domain name service), 214 IP addresses, 211–212 IPv4 addresses, 212 review, 211–214 subnet mask, 214 Neutral, 165 NOC (Network Operation Center), 284 O OFDM (orthogonal frequency division multiplexing) frequency bands, 91 functional blocks, 94–95 interface frames, 91–100 multichannel modulation, 158 symbol details, 92–93 symbols, 88, 91–93 transmission schemes, 92
Index hybrid architecture example, 299 modems, 136–137 optimized, 307–308 See also Wi-Fi “Power line carriers,” 2 Power line communications.
324 Security parameters (home PLC) (continued) configuring, 228–230 firewall, 231–232 PLC gateway, 224–228 testing operation, 230–231 VPN and PPPoE, 232–235 Segment bursting, 53–54 Shared medium architecture, 24–27 analogy with network hub, 25, 26 PLC repeater concept, 25–27 private networks, 24–25, 26 public networks, 24, 25 See also Architecture SHA (Secure Hash Algorithm), 71 Signal injectors, 141–142 Single-phase wiring, 160, 161–163 defined, 160 topology illustrations, 162 See also Three-phase wiring
Index Transmission channel (continued) segment bursting, 53–54 synchronization and frame controls, 49–51 Transmission power, 158–160 Transmission time, 173, 175 3-DES, 64 Trojan horse attacks, 72 Twofish, 65 U Unicast, 58–59 USB device configuration, 183–187 modems, 132–133, 134 V VCS (virtual carrier sense), 39, 52 VDSL bands, 304 Video, 112 routing, 113 surveillance, 118–119 Videoconferencing, 114 Virtual private networks (VPNs), 85 business PLC, 260 home PLC, 232, 234 Viruses, 72 Visioconferencing, 11
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