[Madwifi-users] Throughput tests with madwifi and hostap/wpasupplicant

[Jim Thompson]

On Mar 22, 2006, at 10:45 AM, Beat Meier wrote:

> Hi all
>
> I've done some throughput tests with iperf.
>
> Configuration
> **************
>   AP: wrap2c, SR5
>   Client: wrap2c, CM9
> Software: madwifi-ng-1457, hostapd/wpa_supplicant-0.5.2 using WPA-PSK
> Rate was set fixed to the value indicate on ap and client.
> This is done with 802.11a (5.825 GHz)
> This was done without long distance i.e. only 4m but values
> of cts etc. are set to 6000m!!
> iperf was done at least 15 times per rate and the values were very  
> equal
> (iperf has default tcp window size (client: 16 Kbyte, server: 85.3  
> KByte)
> This has not been in the past!! It seems that either madwifi (which is
> more probable) or hostap/wpa_supplicant has changed to the good  
> site!!!
> In the past I had "fluctuations" about 3-4Mbps now around 0.1Mbps
>
> Iperf server on cliente wrap
> Iperf client from gatway before AP ie.e
> gw -> ap -> client
>
>
> Testresults
> ***********
>
>  6M:  4.3 Mbps (28%)
>  9M:  6.6 Mbps (27%)
> 12M:  8.2 Mbps (32%)
> 18M: 12.6 Mbps (30%)
> 24M: 16.0 Mbps (34%)
> 36M: 21.6 Mbps (40%)
> 48M: 25.7 Mbps (46%)
> 54M: 29.2 Mbps (46%)
>
> The percentage is the overhead (loss of bandwidth) at this rate.
>
> I've seen a lot of mails about asking max. throughput on wrap and
> that's cpu limited to max. 20Mbps but this seems not to be true as  
> seen by
> 48M,54M.

I can get around 30Mbps on freebsd, too.

> Has anybody more better results??
>
> Now my question.
> Does anybody know because until 18M (24M) the protocol overhead or  
> whatever
> is about 30%
> and later there is going to 45%?
> Is it because other modulation? (BPSK,QPSK,16-QAM,64-QAM). Has anybody
> information
> which modulation is used at which rate?
> Retries were in the normal range (I think).

If I had to guess, you're dropping more packets at the higher  
modulation rates.  At 48Mbps and 54Mbps, you're typically limited by  
EVM, not SNR.

Jim