DEPLOYMENT GUIDE Best Practices Guide for Deploying SpectraLink e340, h340 and i640 Wireless Telephones May 2009 Version G
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide Table of Contents 1 Introduction........................................................................................................................... 3 1.1 1.2 1.3 2 SpectraLink e340/h340/i640 Wireless Telephones..................................................................... 3 SpectraLink Infrastructure ...........................................................................................................
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 1 Best Practices Guide Introduction Wi-Fi telephony, also known as Voice over Wireless LAN (VoWLAN), delivers the capabilities and functionality of the enterprise telephone system in a mobile handset. The Wi-Fi handset is a WLAN client device, sharing the same wireless network as laptops and PDAs.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide For additional details on any of these products visit the Polycom web site. 1.3 VIEW Certification Program The VIEW Certification Program is a partner program designed to ensure interoperability and maximum performance for enterprise-grade Wi-Fi infrastructure products that support Polycom’s SpectraLink e340/h340/i640 and 8020/8030 Wireless Telephones and their OEM derivatives.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 2 Best Practices Guide Wireless LAN Layout Considerations SpectraLink handsets utilize a Wi-Fi network consisting of WLAN access points (APs) distributed throughout a building or campus. The required number and placement of APs in a given environment is driven by multiple factors, including intended coverage area, system capacity, access point type, power output, physical environment, and radio types. 2.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide The WLAN layout must factor in the transmission settings that are configured within the APs. The transmission of voice requires relatively low data rates and a small amount of bandwidth compared to other applications. The 802.11 standard includes automatic rate switching capabilities so that as a user moves away from the AP, the radio adapts and uses a less complex and slower transmission scheme to send the data.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide ten decibels higher for the handset to return to the previously associated AP. This behavior requires that the assessment area must have at least a ten decibel difference to enable good roaming behavior for all cases. Corners and doorways pose a particular design issue. The shadowing of corners can cause steep dropoffs in signal coverage.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide SpectraLink handsets have a Site Survey mode that can be used to validate the signal strength it is receiving from the AP. The handset also has a Diagnostics mode which can show AP signal strength, as well as other details, as received during a call. See the SpectraLink e340/h340/i640 Wireless Telephone Administration Guide for details on using the Site Survey and Diagnostics mode features.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide If adjacent access points in three dimensions (above, below or beside) are set to the same channel, or utilize channels with overlapping frequency bands, the resulting interference will cause a significant reduction in the network performance and throughput, and will degrade overall voice quality.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide AP utilizes all three radios types, AP placement should first be determined by modeling for the characteristics of 802.11a, since this environment will typically have the shortest range. Then, the transmit power of the 802.11b and 802.11g radios should be adjusted to provide the required coverage levels and cell overlap for those networks, within the already established AP locations. 2.2.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide Access point antennas should not be placed near a metal roof, wall, beam or other metal obstruction in any environment, as this will amplify the reflection effects. Additionally, antennas should be positioned so that they have line of sight (LoS) to most of the clients that they service.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide may be able to support. This allows some telephones to work at lower rates (1Mbps and 2Mbps) and some at the highest data rates. 2.3.1 Access Point Bandwidth Considerations There are several factors which determine the AP bandwidth utilization during a telephone call. The first is the VoIP protocol used and its characteristics.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide 2.3.2 Push-to-Talk Multicasting Considerations SpectraLink i640 handsets provide push-to-talk (PTT) functionality using the Polycom-proprietary SpectraLink Radio Protocol (SRP) ADPCM encoding. Because the PTT mode uses IP multicasting, all APs on the subnet will transmit a PTT broadcast.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide the AP coverage supports 12 simultaneous calls per AP, each AP can then support approximately 39 moderate users. This allows some users to be in-call and others in standby. The Table 2 shows maximum users per AP based on the AP’s ability to handle simultaneous calls: User Calling Intensity Light Moderate Heavy Erlangs per User 0.10 0.15 0.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 3 Best Practices Guide Network Infrastructure Considerations 3.1 Physical Connections SpectraLink infrastructure components, including the SVP Server(s), Telephony Gateways and OAI Gateway, must connect to a facility’s LAN using enterprise-grade Ethernet switches rather than Ethernet hubs or consumer-grade SOHO switches in order to provide adequate bandwidth and limit traffic collisions and bottlenecks (see Figure 4 for reference).
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide SVP Server Wi-Fi AP Telephony Gateway Connect to either PBX or call server PBX PSTN Ethernet Switch call server Wi-Fi AP WLAN Controller SpectraLink e340/h340/i640 Wireless Telephone TFTP Server (Download handset software) Figure 4 – Physical Connections Assigning IP Addresses 3.2 SpectraLink handsets operate as LAN client devices and therefore require IP addresses to operate in the network.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide When operating with an IP telephony server (IP PBX), other than Avaya or Cisco, the SVP Server also requires a range of IP addresses that cover the total number of wireless telephones supported by that SVP Server. That range of IP addresses is known as First Alias IP Address/Last Alias IP Address in the SVP Server configuration menu.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 4 Best Practices Guide SpectraLink Voice Priority (SVP) Polycom pioneered VoWLAN for the enterprise and remains the market leader today. One key success factor has been our SpectraLink Voice Priority (SVP) mechanism for QoS. This method is proven to deliver enterprise-grade voice quality, battery life and call capacity for SpectraLink handsets.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide most instances, because of the large number of wireless telephones and APs expected in such an application, the distribution of call processing will be relatively even across all SVP Servers. Some installations with multiple SVP Servers (SVP code < 17x.033) are configured to have primary (“master”) and one or more secondary servers.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Manage voice packet delivery by the AP Best Practices Guide Limit maximum handsets in-call per AP (static number entered by administrator) Limit maximum handsets in-call per AP (static number entered by administrator) Receive packets from the ‘home’ Receive packets from the ‘home’ SVP Server and forward to handset SVP Server and forward to handset though currently associated AP though currently associated AP Table 4 – SVP Server Functions The
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide o When handset 2 is using AP B it receives packets from SVP 2 o When handset 2 is using AP C it receives packets from SVP 2 o When handset 2 is using AP D it receives packets from SVP 1 Handset 3 registers with SVP Server 2 o Handset 3 always sends its packets to SVP 2 − SVP 1 forwards handset 3 audio packets to the call server or PBX − The call server or PBX sends audio packets from the telephone this handset is in call
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide Figure 7 - Scenario Two Calls between handset may bypass the call server or PBX and connect directly between SVP Alias IP addresses. Control messaging will still go to /from the call server or PBX. As a final note, the wireless telephone learns about all available SVP Servers IP addresses when it powers up and does the “SRP Check-In” with the Registration SVP Server (identified in DHCP option 151 or set statically).
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide and performance. Even systems that are implemented with only voice and no data clients there is still a need for QoS to ensure background services do not interfere with the audio. The SVP Server is responsible for providing packet prioritization and timed release for specific time slot deliveries to all wireless phones.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 5 Best Practices Guide Security Proper security provisions are critical for any enterprise Wi-Fi network. Wireless technology does not provide any physical barrier from malicious attackers since radio waves penetrate walls and can be monitored and accessed from outside the facility. The extent of security measures used is typically proportional to the value of the information accessible on the network.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide forward these tags, but are otherwise compatible with 802.1Q up to the Ethernet switch ports used for the SpectraLink equipment. 5.4 MAC Filtering and Authentication Most access points can be configured to allow or deny association of wireless clients based on their unique MAC address, which can be used as a method of securing the WLAN.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide Most voice devices, such as the SpectraLink Wireless Telephones, do not require access to the protected portion of the network (see Figure 8). Placing the handsets, SVP Server(s) and Telephony Gateways on the unprotected network and requiring data users to connect to the VPN ensures that the network is protected against hackers seeking to access sensitive information within the network core.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 6 Best Practices Guide Subnets, Network Performance and DHCP Subnets are used to create a boundary between network segments. Although these boundaries are logical, they become like a physical boundary for mobile network devices moving throughout the enterprise. When a device with an established IP data stream (such as with an active phone call) attempts to roam across a subnet boundary, it must obtain a valid IP address within the new subnet.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide In one deployment scenario for accommodating multiple subnets, each subnet is treated independently with respect to the SVP Servers and wireless network, but each subnet can still provide service to a single IP telephony server. One or more SVP Server(s) can be deployed on each subnet just as with a single subnet system, including identifying the registration SVP via DHCP option 151 or static configuration.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide Figure 9 - Measuring Network Jitter In a multiple SVP Server configuration, jitter is measured from the SVP Server that is responsible for the traffic through a given AP to a wireless telephone. This may be different than the SVP Server that is acting as a proxy for the wireless telephone to the IP PBX. Refer to Section 4.1.3 for additional multiple SVP Server information.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 Best Practices Guide to locate and register with the Telephony Gateway. Once the handset registers, the remaining options that would normally be handled via DHCP, such as TFTP, are provided by the Telephony Gateway. When the license option in the wireless phone is set for one of the IP protocols the handset will require several other DHCP options in order to function properly.
Deploying SpectraLink 8020/8030 Wireless Telephones May 2009 7 Best Practices Guide Conclusion The SpectraLink e340/h340/i640 Wireless Telephone uses Wi-Fi technology to deliver a full-featured mobile extension to a call server or PBX. The purpose of this document is to outline the network design criteria for a successful VoWLAN deployment. By applying the guidelines described in this document, networking and telephony professionals can confidently design and deploy a Polycom Wi-Fi telephony solution.
