There is always a tradeoff between speed and coding. The problem is that the highest speeds already have rather limited link budgets; if you reduce or eliminate the FEC the required S:N goes up. This is probably fine if you are doing a line-of-sight link in the same room for a video delivery, but not so good farther away. A nice reference you can check out is
A Comparison of HIPERLAN/2 and IEEE 802.11a
Angela Doufexi1, Simon Armour1, Peter Karlsson1,2, Andrew Nix1, David Bull1
1Centre for Communications Research, University of Bristol, UK
2Telia Research AB, Malmoe, Sweden
E-mail: [EMAIL PROTECTED], [EMAIL PROTECTED]
Unfortunately I don't know where this was published but you can get it from the U Bristol folks directly over the web. They did a followup paper coupling these results to propagation modeling as well.
--Dan Dobkin
On Friday, July 11, 2003, at 04:33 PM, Akash Malhotra wrote:
Dear Mr Dobkin,Daniel M. Dobkin
Thanks for the reply. I am student whose interest lies in wireless
networks especially 802.11 technology. I just got curious to find out
be cause I read somewhere that few comapnies are trying to reduce this
overhear(FEC) to increase speed to 72 Mbps.
Thanks
akash
On Fri, 11 Jul 2003, Daniel Dobkin wrote:
Response to post of 7/11:
<<Is it compulsary to use FEC with OFDM technology
such as 802.11 a/g. (?)>>
It is certainly not compulsory to employ FEC with any OFDM technology;
OFDM is a modulation technique quite independent of encoding. However,
it certainly is compulsory to employ this method in 802.11a (and g), as
encoding is part of the standard.
An encoded data stream is incomprehensible unless you decode it, so one
could not use FEC on only one end of a link. It is certainly possible
to use FEC in only one direction on a link, presupposing that both
stations are coordinated (that is, EAST transmits coded messages to
WEST, WEST receives and decodes; WEST transmits unencoded messages to
EAST, which receives them and passes them without decoding). It's
unlikely such an arrangement would be worthwhile.
Why do you want to turn off encoding?
Daniel M. Dobkin
Enigmatics
1-408-314-2769
[EMAIL PROTECTED]
Enigmatics
1-408-314-2769
[EMAIL PROTECTED]
