Jon gives an excellent summary of the current situation. I'll elaborate
slightly on a few points....
There is a real issue with 802.11n in 40MHz channels, one that was not
perceived long ago.
This issue was raised quite some time ago. That is one reason it has become
a bit contentious now. 'nuff said...
As it is described right now, the expectation by a
number of 802.11 voters is to allow 2 channels of non-overlapping
40MHz-wide operation in the US 2400-2483.5MHz band (and likely in other
regions/countries as well). If there is agreement on this, there will be
locations (likely many) where both 40MHz channels are occupied and used
intensively. With two heavily loaded 11n channels and a number of hidden
transmitters, it may prove difficult for 802.15.4 stations to compete
successfully as there will be NO clear channels and only the temporal
agility of the 15.4 radio gives it a chance to communicate.
Additionally, the usage models and applications discussed by TGn raise
concernes of near 100% occupation in time as well as frequency. Systems such
as Bluetooth and 802.15.4 depend on other services leaving some time to
squeak in, as well. There is a perception that 11n may completely fill the
band in frequency and in time, which presents much greater conflict than
with the typical usage models of today. The most common usage of 802.11g
today is connecting to the internet, which usually involves a bottleneck of
6MBps or less between the user and the internet. Thus actually air duty
cycle for the most common 11g usage scenarios leaves a lot of room in time
for other services. Thus explanations offered by TGn based on similarity of
channel bonding to having multiple 11g APs in the same space have been less
than reassuring. I think this is significant.
Another factor is that while operating under the same rules, it is likely
802.15.4 nodes will be operating at much lower effective transmit power than
11n (due to focus on low power, low cost implementation).
Alas, the same factors that make 802.15.4 unlikely to interfere with, and
likely to "lose" contention with an 11n system, also make 15.4 neighbors
harder for other services such as 11n to detect.
-Ben
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Geoff Mulligan
Sent: Monday, July 07, 2008 8:31 AM
To: Mustafa Hasan
Cc: [email protected]
Subject: Re: [6lowpan] Regarding coexistence with 802.11n
Appendix E of the 802.15.4 standard goes into detail on co-existence.
On Fri, 2008-07-04 at 09:04 -0700, Mustafa Hasan wrote:
Dear 6lowpaner,
I need little help regarding the coexistence issue of ISM Band with
other ISM, especially with the 802.11n, 802.11b.
I want to know what are the factor is going to save the 802.15.4
fighting with others frequency.
Thanks in Advance...
Regards
M. Hasan
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