Section 802.11. bFirst, But Fading Away

802.11. bFirst, But Fading Away

Although IEEE 802.11b is the least expensive wireless technology, it is no longer the most popular because 802.11g hardware can interoperate freely with 802.11b hardware (both use the 2.4GHz frequency band) and because 802.11g hardware provides greater performance and supports newer security standards than does 802.11b.

While the IEEE was still debating (seemingly endlessly) about the specifications for the IEEE 802.11a standard, the working group for the 802.11b standard got to the finish line first. Thus, in order of adoption, the three standards look like this (earliest to latest):

802.11b, 802.11a, 802.11g

802.11b hardware is sometimes referred to as Wi-Fi hardware because it was the first type of 802.11-compatible wireless hardware to undergo Wi-Fi Alliance certification tests. Other popular terms for 802.11b hardware include Wireless-B and 11Mbps.

See "Why Wi-Fi?," p. 299, for more information about the Wi-Fi Alliance.

802.11. b/g Channels

Although 802.11b and 802.11g use the 2.4GHz frequency band for signaling, the frequency is divided into 11 channels for use in the United States and Canada (some countries allow as many as 14 channels). Table 19.1 shows the channel frequencies supported in the United States and Canada. The effective width of each signal is about 11MHz on either side of the nominal frequency.

Table 19.1. United States/Canada 802.11b/g Channel Frequencies

Channel	Nominal Frequency (MHz)	Minimum (MHz)	Maximum (MHz)
1	2412	2401	2423
2	2417	2405	2428
3	2422	2411	2433
4	2427	2416	2438
5	2432	2421	2443
6	2437	2426	2448
7	2442	2431	2453
8	2447	2436	2458
9	2452	2441	2463
10	2457	2446	2468
11	2462	2451	2473

Channels 1, 6, and 11 are recommended because there is a lower potential for interference from other 802.11b/g APs when these channels are used. If you need only a single AP to provide coverage for your location, use one of these channels. If you need to set up multiple APs to cover your location, you should use two or all three of these channels. Studies by Cisco Systems suggest that throughput drops because of interference if you attempt to use more than three channels in a multiple-AP scenario.

Proprietary Extensions to 802.11b

Two main factors are encouraging the replacement of 802.11b wireless networks with 802.11g or 802.11a-based networks: network speed and network security.

The maximum data rate that 802.11b-based wireless networks support is a relatively slow 11Mbps. In practice, the actual throughput is usually half that value or less due to the distance between the AP and client devices, obstructions weakening radio signals, and the additional overhead of handshaking and security.

In an attempt to improve the performance of 802.11b-based hardware, some manufacturers rolled out proprietary extensions to 802.11b networks. Some of these include D-Link (AirPlus Enhanced; 22Mbps), U.S. Robotics (22Mbps), SMC (Barricade Turbo; 22Mbps), and Alloy (22Mbps). Most of these products were based on the Texas Instruments TI ACX100 chipset, and almost all of them are now discontinued in favor of 802.11g.

The main problem with using proprietary extensions to a standard wireless technology is that all APs and clients must support the same standard or the network will run at standard speeds only. In practice, this means you must usually purchase Access Points and client hardware from the same vendor. Making an across-the-board change is often not practical in terms of cost, and is not practical if many of your PCs use built-in standards-based wireless network adapters, as many notebook computers, PDAs, and smartphones now do.

Generally, 802.11-based network hardware supports only first-generation wireless security, Wireless Equivalent Privacy (WEP), as discussed in detail in Chapter 23, "Security and Other Wireless Technologies." Unfortunately, WEP is not nearly as secure as newer standards and someone that knows what he's doing can easily get around WEP security. Some 802.11b hardware can be upgraded to implement the improved Wi-Fi Protected Access (WPA) standards. If you want the superior security of WPA on a mixed 802.11b/802.11g or 802.11b/802.11a network, you must upgrade your 802.11b clients to WPA, if possible, or replace your hardware. Generally, you would use 802.11g hardware as a replacement for 802.11b because both use the same 2.4GHz frequency and can interconnect with each other natively.