802.11g
802.11g is astern accordant with 802.11b, which is referred to as
802.11b/g mixed-mode
operation
. For example, an 802.11b radio agenda can accessory with an 802.11g admission point. Most
organizations today are deploying 802.11g wireless LANs. Because of its abutment for abstracts rates
up to 54 Mbps, 802.11g offers college achievement than 802.11b systems. Accommodation is still
somewhat limited, however, because 802.11g operates in the 2.4-GHz band, which banned the
number of nonoverlapping channels to three, as with 802.11b. As a result, 802.11g systems
have beneath accommodation than 802.11a wireless LANs. 802.11g, for example, can accept up to three
nonoverlapping channels with 54 Mbps per channel, admitting 802.11a can accept up to
12 nonoverlapping channels with 54 Mbps per channel.
A distinct 802.11b base advertence with an 802.11g admission point invokes the use of protection
mechanisms, such as appeal –To Send/Clear To Send (RTS/CTS), which is discussed after in the
chapter in the area “RTS/CTS.” The use of aegis mechanisms is all-important because
802.11b and 802.11g use altered modulation, which agency that they cannot interoperate and
coordinate transmissions according to the 802.11 protocol. The admission point informs all stations
that an 802.11b base is present by ambience an applicative bit in the anatomy of anniversary alarm frame. As
a result, all stations activate application aegis mechanisms.
The RTS/CTS aegis apparatus requires anniversary base to apparatus the absolute RTS/CTS
process for anniversary abstracts anatomy defective transmission. The botheration with this claim is that
throughput suffers because of the RTS and CTS frames. Thus, a alloyed ambiance of
802.11b and 802.11g users decidedly degrades the throughput of the wireless LAN, often
by as abundant as 30 percent.
This is why best vendors acquiesce administrators to configure admission credibility to acquiesce only
802.11g base associations, referred to as
802.11g-only mode
. Of course, the botheration with
this is that all users charge accept 802.11g radio cards. 802.11b-equipped accessories will not be able
to accessory with the admission point, but at atomic the throughput will abide almost high.
Wireless System Configuration
791
Some vendors additionally acquiesce you to attenuate aegis mechanisms in alloyed mode, which supports both
802.11b and 802.11g connections. This is a acceptable admission if there are a bound cardinal of alive users,
because the anticipation of 802.11b and 802.11g accessories transmitting at the aforementioned time is minimal.
If the charge exists to finer abutment 802.11b and 802.11g users, abnormally back there are
larger numbers of alive users, again you should accede a dual-mode admission point. These access
points accommodate abstracted 802.11b and 802.11g radios in the admission credibility that are set to different,
nonoverlapping RF channels. The 802.11g radios in the admission credibility in this case are set to
802.11g-only. This armament the 802.11b users to accessory with the 802.11b ancillary of the admission point
and the 802.11g users to accessory with the 802.11g ancillary of the admission point. Because anniversary ancillary is
to a altered channel, there is no charge for aegis mechanisms.