User's Manual

Chapter 1: Introduction
IEEE 802.11b Protocol
8 Teklogix 9150 Wireless Gateway User Manual
1.5.1 IEEE 802.11b Protocol
The IEEE 802.11b protocol is an OSI standard for Wireless Local Area Networks
(WLANs). With this standard, any IEEE 802.11b radio can communicate with any
other similarly-equipped device. However, IEEE 802.11b does not provide a stan-
dard for a total WLAN system. IEEE 802.11b solely standardizes two communica-
tions layers: Physical (PHY) and Medium Access Control (MAC). Three different
PHY layer media are covered: 2.4 GHz Direct Sequence Spread Spectrum radio,
2.4 GHz Frequency Hopping Spread Spectrum radio, and infrared. Each station
in a WLAN system has its own unique MAC address.
Important: Equipment using one physical medium (e.g. Frequency Hopping
versus Direct Sequence) will not interoperate with equipment
using a different physical medium.
IEEE 802.11b uses 2.4 GHz radios of relatively low power. The range is limited
to no more than a hundred feet or so, depending on the conditions, and is usually
restricted to “line of sight” operation. Therefore, most wireless networks need more
than one coverage area, with terminals moving between the areas. To integrate
those areas, systems using IEEE 802.11b protocol for their wireless networks
require an IEEE 802.11b-equipped bridge device (or access point), such as the
9150 Wireless Gateway.
Using bridging software, the 9150 Wireless Gateway enables communication
between any wireless IEEE 802.11b-equipped stations and LAN stations operating
on Ethernet. The 9150 itself is resident on the LAN and functions as a MAC bridge,
providing transparent integration between the stations on the wireless and
wired networks.
Each terminal is associated with one 9150. A frame from an RF terminal is sent to
the 9150 that the terminal is associated with. The terminal puts a destination MAC
address in the frame, which specifies a hardware address on the wired LAN side.
Because the receiving 9150 is connected to an Ethernet network, it encapsulates the
data in an Ethernet frame, including the destination MAC address specified by the
terminal. The 9150 then sends the frame onto the physical network; the frame is
picked up by whichever device is at the destination hardware address.
When sending frames from the LAN side, the sending device puts the MAC address
of the terminal in the frame header. Whichever 9150 has that terminal associated
with it, takes the frame and passes it over the RF to the terminal. By passing frames
in this way, the 9150 is acting as a MAC bridge.