WESM zl Management and Configuration Guide WT.01.28 and greater

1-52
Introduction
Radio Ports
The 802.11a standard enables data rates from 6.0 Mbps to 54 Mbps, depending on
the quality of the signal level. Overhead and competition for the shared medium often
lowers actual throughput to about half the theoretical data rate.
The second radio on the RP 220 and on the RP 230 supports 802.11a.
802.11b. This standard defines the Physical Layer for wireless networks that operate
in the 2.4 GHz band—one of the radio bands available to any private entity.
This band includes channels 1 to 14, some of which, however, are not allowed in
certain regions. The channels overlap, each creating noise in the five channels on
either side. Non-overlapping channels include:
■ 1, 6, and 11
■ 1, 7, and 13
802.1b enables data rates between 1 Mbps and 11.5 Mbps, although overhead
decreases the actual throughput by at least half.
Although 802.11g is replacing 802.11b, some older stations still support only
802.11b. The RP 210’s single radio and the first radio on the RP 220 and the RP 230
support 802.11b.
802.11g. 802.11g operates in the 2.4 GHz range like 802.11b. However, it enables
the higher data rates of 802.11a—between 6.0 Mbps and 54 Mbps (although, again,
overhead decreases the actual throughput).
The RP 210’s single radio and the first radio on the RP 220 and the RP 230 also
support 802.11g. 802.11g is backward compatible with 802.11b, so the radio can
support both standards at once. This guide refers to the RP radios that support 802.11b
and 802.11g as 802.11bg radios.
By default, an RP’s 802.11 bg radio supports both 802.11b and 802.11g stations. You
can remove support for 802.11b stations by requiring 802.11g’s short preamble and
removing the 802.11b rates for the radio’s basic rate set. See Chapter 3: “Radio Port
Configuration” for more information.
802.11h. 802.11h consists of two mechanisms: Dynamic Frequency Selection (DFS)
and Transmit Power Control (TPC). DFS enables RPs to dynamically change channel
if they detect interference on a channel. RPs use TPC to lower their power, and that
of associated stations, and minimize interference.
Many countries require support for 802.11h as a condition to using certain 802.11a
channels. The countries operate military radar on those channels; With 802.11h, the
private radios to share the channels without interfering with the military.