Low Wi-Fi throughput

[Arend van Spriel]

On 12/16/2013 11:16 AM, Alban JEANTHEAU wrote:
> Hi Antonio,
> 
>   Thank you for your answer. Please find my comments below:
> 
> 
> *> why using WPA-NONE when you can use RSN ? WPA-NONE is not really WPA..>
> How can you use CCMP with WPA-NONE?*
> 
> To be honest I didn't focus on key / ciphering configuration, and I copy an
> existing configuration found somewhere. However
> http://hostap.epitest.fi/gitweb/gitweb.cgi?p=hostap.git;a=blob_plain;f=wpa_supplicant/wpa_supplicant.conf
>  states:
> # mode: IEEE 802.11 operation mode
> 
> # 0 = infrastructure (Managed) mode, i.e., associate with an AP (default)
> # 1 = IBSS (ad-hoc, peer-to-peer)
> # 2 = AP (access point)
> # Note: IBSS can only be used with key_mgmt NONE (plaintext and static WEP)
> # and key_mgmt=WPA-NONE (fixed group key TKIP/CCMP). WPA-None requires
> # following network block options:
> # proto=WPA, key_mgmt=WPA-NONE, pairwise=NONE, group=TKIP (or CCMP, but not
> # both), and psk must also be set.
> 
> 
> *>     htmode=HT40-*
> 
> If I don't set htmode, I'm stuck with 54Mbps. If i set htmode=HT20, I
> can use 72.2Mbps, if I set htmode=HT40- I can use 150Mbps. And you
> guess right I am using openwrt, sorry for not mentionning it...
> 
> ht_capa file of my peer:
> 
> ht supported
> cap: 0x02f2
>     HT20/HT40
>     Static SM Power Save
>     RX Greenfield
>     RX HT20 SGI
>     RX HT40 SGI
>     TX STBC
>     RX STBC 2-streams
>     Max AMSDU length: 3839 bytes
>     No DSSS/CCK HT40
> ampdu factor/density: 3/4
> MCS mask: ff ff 00 00 01 00 00 00 00 00
> MCS tx params: 7
> 
> I am not sure I understand everything here. Why bit 19 is set in MCS
> mask?

I guess you mean bit 32. It is set because you have 40 MHz.

 What MCS tx params is? Only one stream in Tx?

/* 802.11n HT capability MSC set */
#define IEEE80211_HT_MCS_RX_HIGHEST_MASK	0x3ff
#define IEEE80211_HT_MCS_TX_DEFINED		0x01
#define IEEE80211_HT_MCS_TX_RX_DIFF		0x02
/* value 0 == 1 stream etc */
#define IEEE80211_HT_MCS_TX_MAX_STREAMS_MASK	0x0C
#define IEEE80211_HT_MCS_TX_MAX_STREAMS_SHIFT	2
#define		IEEE80211_HT_MCS_TX_MAX_STREAMS	4
#define IEEE80211_HT_MCS_TX_UNEQUAL_MODULATION	0x10

So indeed it seems only one tx stream.

Gr. AvS

> Alban
> 
> 
> 
> 
> On Fri, Dec 13, 2013 at 6:11 PM, Antonio Quartulli
> <antonio at meshcoding.com>wrote:
> 
>> Hi Alban,
>>
>> On 13/12/13 18:06, Alban JEANTHEAU wrote:
>>> Hi every one,
>>>
>>>   I need to make Wi-Fi connections between my device and I require a
>>> high throughput. I mainly target IBSS network. For IBSS, I'm using
>>> wpa_supplicant with USB dongle Asus N53 (RT3572, here is my
>>> configuration file:
>>>
>>> ap_scan=2
>>> network={
>>>     scan_ssid=1
>>>     ssid="MySsid"
>>>     frequency=5200
>>>     mode=1
>>>     key_mgmt=WPA-NONE
>>
>> why using WPA-NONE when you can use RSN ? WPA-NONE is not really WPA..
>>
>>>     proto=WPA
>>>     psk="MyKey"
>>>     pairwise=NONE
>>>     group=CCMP
>>
>> How can you use CCMP with WPA-NONE?
>>
>>>     htmode=HT40-
>>
>> where have you seen this parameter? This is not supported by
>> wpa_supplicant as it is nl80211 specific....and we didn't find a
>> reasonable way to push into the configuration engine any driver-specific
>> parameter.
>>
>> Are you using openwrt by any chance?
>>
>>> }
>>>
>>> The maximum throughput I can reach is about 22Mbps (iperf TCP between 2
>>> devices 2 meters away).
>>
>> My guess is that the IBSS connection is not exploiting the HT
>> capabilities. Please, look for a file called ht_capa in /sys/ (you
>> should have one of this file for each peer you have) and check its content.
>>
>>
>> Cheers,
>>
>>
>> --
>> Antonio Quartulli
>>
>>
> 
> 
> 
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