On Sun, 06 Apr 2008 15:33:13 -0400, mm <(E-Mail Removed)>
wrote:
>Does every wireless g router also transmit b?
The default is to enable 802.11b compatibility. I sometimes turn it
off.
The problem with "b" is not speed. It's the air time it occupies.
Data sent at 1Mbits/sec, the slowest 802.11b speed, occupies about 8
or 9 times as much air time as the same data sent at 6Mbits/sec, the
slowest 802.11g (OFDM) speed. If the airspace is saturated with a
large number of users, 802.11g can ideally handle 8 times as many
users, assuming they're running at the slowest speed (a good
assumption as multiple collisions will cause the access point to
switch to the slowest speeds in an attempt to recover).
There are other problems with 802.11b. With 802.11b compatibility
enabled in the wireless access point, all management packets and
broadcasts are sent at the slowest (and longest) 1Mbit/sec speed. Turn
off 802.11b compatibility, and 802.11g sends them at 6Mbits/sec, the
slowest 802.11g speed.
802.11b also has problems dealing with reflections, multipath, and
frequency selective fading. 802.11g OFDM modulation is far more
resistant to these problems. One would assume that this would not be
a common problem, but I'm finding it all too common.
For example, one of my coffee shop customers is in an octagon shaped
brick building. The place is one big mess of reflections. It's even
difficult to hear onself talk through all the noise and echos. I was
getting erratic download speeds and even some disconnects, for no
obvious reason. Monitoring the wireless router, I found far too many
users connecting at 802.11b speeds. I assumed that this was caused by
interference and reflections. So, I just turned off 802.11b
compatibility. The disconnects instantly ceased, and the erratic
performance was hugely reduced. So were the complaints.
I assumed that there would be problems with users having only 802.11b.
So, I hung up a small sign, under the "we have free wi-fi" sign, that
announced the 802.11b is not supported. There were a few complaints,
that I "solved" by explaining why they should buy a better wireless
adapter. There was also one issue that caught me by suprise. Many
802.11g USB dongles revert to 802.11b only mode if shoved into a USB
1.1 port. The device can easily do 802.11g speeds, but the authors of
the device drivers seem to think that flow control is evil, and that
the wireless speed should be slowed down to match the interface speed.
I can see the logic, but this has given me problems with some users.
There are also some PDA's that do not support 802.11g. For example,
my Verizon XV-6700 only does 802.11b, but does to WPA encryption.
There are other PDA's and cell phones with similar configurations.
At this time, some of my wireless routers have 802.11b enabled, while
others have it turned off. It varies by location, owner politics, and
class of users. If it's a high traffic and high user count system,
802.11b is OFF. If it's light use, then I leave it on.
--
Jeff Liebermann
(E-Mail Removed)
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558