802.11a/b/g Performance Chart

I keep getting asked "how fast can it go" type questions. Perhaps
some numbers might help. This is stolen from an Atheros PDF at:
http://www.atheros.com/pt/atheros_range_whitepaper.pdf
with some additions and corrections by me.


Non-overlapping Modulation Max Max Max
Channels ------- | Link TCP UDP
| | | | |
802.11b 3 CCK 11 5.9 7.1
802.11g (with
802.11b) 3 OFDM/CCK 54 14.4 19.5
802.11g only 3 OFDM 54 24.4 30.5
802.11g turbo 1 OFDM 108 42.9 54.8
802.11a 13 OFDM 54 24.4 30.5
802.11a turbo 6 OFDM 108 42.9 54.8

The paper claims that encryption is enabled for these calculations,
but my numbers seem to indicate that these number are for encryption
disabled. Dunno for sure. The Max TCP and Max UDP are the
theoretical maximum thruput rates.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

On 12/31/04 7:49 PM, Jeff Liebermann wrote:

> Non-overlapping Modulation Max Max Max
> Channels ------- | Link TCP UDP
> | | | | |
> 802.11b 3 CCK 11 5.9 7.1
> 802.11g (with
> 802.11b) 3 OFDM/CCK 54 14.4 19.5
> 802.11g only 3 OFDM 54 24.4 30.5
> 802.11g turbo 1 OFDM 108 42.9 54.8
> 802.11a 13 OFDM 54 24.4 30.5
> 802.11a turbo 6 OFDM 108 42.9 54.8

What does the "802.11g (with 802.11b)" mode mean exactly?

Does it mean an 802.11g AP with active 802.11b clients or just the
activation of compatibility setting in the AP config, even if there are
no active 802.11b clients?

Thanks.

On Sun, 02 Jan 2005 18:04:54 +0100, meATprivacyDOTnet <(E-Mail Removed)>
wrote:

>On 12/31/04 7:49 PM, Jeff Liebermann wrote:
>
>> Non-overlapping Modulation Max Max Max
>> Channels ------- | Link TCP UDP
>> | | | | |
>> 802.11b 3 CCK 11 5.9 7.1
>> 802.11g (with
>> 802.11b) 3 OFDM/CCK 54 14.4 19.5
>> 802.11g only 3 OFDM 54 24.4 30.5
>> 802.11g turbo 1 OFDM 108 42.9 54.8
>> 802.11a 13 OFDM 54 24.4 30.5
>> 802.11a turbo 6 OFDM 108 42.9 54.8
>
>What does the "802.11g (with 802.11b)" mode mean exactly?

It means that there is a beaconing 802.11b access point in the
vicinity, with a connected 802.11b client, that is NOT moving traffic.
802.11g will slow down to listen for traffic from the 802.11b device
if it hears a beacon. No traffic is necessary to create the slowdown.
The degree of slowdown varies with the type of flow control mechanism.
Since such flow control is usually off by default, the higher value is
used in the table. There are some details in the paragraph under the
table on Page 1.
http://www.atheros.com/pt/atheros_range_whitepaper.pdf

If you want the exact explanation, Atheros also published their test
methods at:
http://www.atheros.com/pt/Methodolog...AN_Chariot.pdf
On Page 3 is proclaims:
"Since the key feature of 802.11g is backward compatibility with
802.11b, throughput tests should be done with an 802.11b client
device connected to the access point but otherwise idle. This setup
ensures that the 802.11g network is operating in an 802.11b
compatible mode."

Other papers are at:
http://www.atheros.com/pt/papers.html
The methodology is similar to those used by the nifty product
performance tests on Tom's Hardware site. For example, here's the
WRT54G:
http://www.tomsnetworking.com/Review...D-WRT54G-9.php

>Does it mean an 802.11g AP with active 802.11b clients or just the
>activation of compatibility setting in the AP config, even if there are
>no active 802.11b clients?

802.11b client connected but not moving any traffic. There are quite
a few beacons and managment frames belched by non-active 802.11b
access points sufficient to drive a typical 802.11g system to a crawl.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

meATprivacyDOTnet <(E-Mail Removed)> wrote:
> On 12/31/04 7:49 PM, Jeff Liebermann wrote:

>> Non-overlapping Modulation Max Max Max
>> Channels ------- | Link TCP UDP
>> | | | | |
>> 802.11b 3 CCK 11 5.9 7.1
>> 802.11g (with
>> 802.11b) 3 OFDM/CCK 54 14.4 19.5
>> 802.11g only 3 OFDM 54 24.4 30.5

> What does the "802.11g (with 802.11b)" mode mean exactly?

> Does it mean an 802.11g AP with active 802.11b clients or just the
> activation of compatibility setting in the AP config, even if there are
> no active 802.11b clients?

I would think it means with both active. My 802.11g router has "b"
enabled, for certain visitors. With just a "g" connected, I get 26.4MBpS
on TCP "iperf" testing. Running iperf -d to test both directions, I get
13.1 Mbits/sec plus 14.6 Mbits/sec. I think that's a point that Jeff has
raised in the past. 54Mbps is shared on the WAP.

I was able to write to a shared Windows disk drive on the wired systems
from the wireless G at about 21Mbps.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5

On 1/2/05 7:13 PM, Jeff Liebermann wrote:

> 802.11b client connected but not moving any traffic. There are quite
> a few beacons and managment frames belched by non-active 802.11b
> access points sufficient to drive a typical 802.11g system to a crawl.

Thanks for the explanation.

Since I am using two WRT54GS wireless routers for a WDS bridge with no
wireless clients, I am going to set them to G-only mode, just to be on
the safe side.

Thanks.