datarate

[yjr1220]

Hello ! my dear!

    I want to know whether the transmission rate can be changed in monitor mode. For example, I can set the rate under 802.11 AC of WiFi card! High speed transmission!  

     best wishes ! 

[svpcom]

Use mcs_index = value in config file and use value from http://mcsindex.com/

[yjr1220]

thank you for reply! in you source code,
int main(int argc, char * const *argv)
{
int opt;
uint8_t k=8, n=12, radio_port=1;
int udp_port=5600;

int bandwidth = 20;
int short_gi = 0;
int stbc = 0;
int ldpc = 0;
int mcs_index = 1;

.......
the bandwidth can set value 80 or 160 ? the mcs_index can set value make the datarate change ? is right ?
and the data rate is only related to mcs_index ?
best wishes !

[svpcom]

You can try to use 80 and/or 160 MHz bandwidth, but I'm not sure that current drivers supports injection of VHT packets. Data rate depends from bandwith and mcs index (see table from link above). But I'll recommend to use only 20MHz bandwidth for long-distance transmissions

[svpcom]

It already supported by driver, but you you need to use different radiotap header contents on wfb_tx and rx side. See for details:
https://github.com/svpcom/rtl8812au/blob/e9fbf5c051453941bbc029810b893a6c010714e6/core/rtw_xmit.c#L4646

[yjr1220]

thank you ! ! !

[yjr1220]

Hi svpcom

  I want to know that data inject under monitor mode must be support by firmware of the wifi chip ?  if not the data packet can not transmit !  is right ? 

   I have a wifi card  rtl8822cs . It can set mode monitor ,but can not transmit data.  so I think  it has not be support by the firmware of the wifi chip.

best wishes!!!

[svpcom]

Packet injection should be supported both by firmware and driver. For example rtl8812au supports injection by firmware, but stock driver doesn't support it (there are special driver with injecton https://github.com/svpcom/rtl8812au).
Most of wifi cards doesn't support injection both by firmware and driver, but supports monitor mode.

[yjr1220]

Oh! I understand. thank you for my reply !

[yjr1220]

hi svpcom !
How can I fix the frequency in some band ? example , I want to use 40 channel 80M bandwidth .
I use VHT injection package, must set the bandwidth right? I am not sure how to fix the mode at 80211.ac under the monitor mode.

best wishes !!!

[yjr1220]

Hi svpcom !

That is to say, there is no need to set bandwidth or hardware mode( B, G, N, AC... And so on). I just set the channel with the (IW) tool, and then set the bandwidth and MCS in your program, right?
your program is：
{
int bandwidth = 20(40,80,160 and so on);
int short_gi = 0;
int stbc = 0;
int ldpc = 0;
int mcs_index = 1(2,3,4,5,6...);
........
}
When I send the inject package it will be sent at the bandwidth and MCS rate set in the program, right?

best wishes !!!

[svpcom]

yes

[yjr1220]

ok , thank you very much!

[yjr1220]

Hi svpcom !

  With your help, I changed the ratio head part into the VHT rate by modifying your code. Debugging the driver shows that the following code does execute. 

#ifdef CONFIG_80211AC_VHT
case IEEE80211_RADIOTAP_VHT:
{
unsigned int mcs, nss;
u8 known = iterator.this_arg[1];
u8 flags = iterator.this_arg[2];
nss = iterator.this_arg[4] & 0x0F; // Number of spatial streams
......
if (nss > 0)
{
if (nss > 4) nss = 4;
mcs = (iterator.this_arg[4]>>4) & 0x0F; // MCS rate index
if (mcs > 8) mcs = 9;
pattrib->rate = MGN_VHT1SS_MCS0 + ((nss-1)*10 + mcs);
if (iterator.this_arg[8] & IEEE80211_RADIOTAP_CODING_LDPC_USER0)
pattrib->ldpc = _TRUE;
}
}
break;
#endif
However, the rate did not change, I tested only 40Mbps. I don't know where the problem is. Could you please help analyze it? The modifications are as follows.
static uint8_t radiotap_header[] attribute((unused)) = {
0x00, 0x00, // <-- radiotap version
0x16, 0x00, // <- radiotap header length
0x00, 0x80, 0x20, 0x00, // <-- radiotap present flags: RADIOTAP_TX_FLAGS + RADIOTAP_VHT
0x08, 0x00, // RADIOTAP_F_TX_NOACK
0x00, 0x45, 0x05, 0x04, 0x82,0x00,0x00,0x00,0x01,0x00,0x00,0x00 //VHT u16 known, u8 flags, u8 bandwidth, u8 cs_nss[4], u8 coding, u8 group_id, u16 partial_aid
// MCS_KNOWN , // bitmap
// 0x00, // flags
// 0x00 // mcs_index
};
When I measured with the spectrograph, the wifi bandwidth was still 20Mz and it didn't change.
thank you !!!

[yjr1220]

Hi svpcom ! So far, I've been working on this problem, but the rate has remained around 30Mbps. Does firmware already limit the transmit rate in monitor mode? best wishes !!!

[svpcom]

Try to capture them via tcpdump or wireshark - are they really transmitted as VHT frames?

[yjr1220]

ok, i'll try!

[yjr1220]

Hi svpcom , I don't know how to test ! tcpdump -i wlan0 right ?