Getting 0x3x114 CSI values

itskalvik commented 5 years ago

I have a WDR4300 router setup with openwrt as the transmitter and a desktop with the ar9590 NIC for the receiver. I forced MCS 16 at 40 MHz (5Ghz) by updating fixed_rate_idx with value 78. But, when I transmit packets, I am getting 0 transmitting antennas and rxs->rs_datalen is 641 in ar9003_csi.c . I tried setting MCS 15 at 40 MHz with 77 in the rate_index_table file and I am getting 2x3x114 CSI values. Not sure why it won't transmit with all antennas when using MCS 16 at 40 MHz. I tried using different routers for transmitting and different desktops with different NICs and got the same issue. I am receiving 3x3x56 CSI values when using MCS 16 at 20 MHz without any issues. I also tried changing the packet length but it still does not work. Any MCS rate over 15 at 40Hz and 5 GHz gives nc = 0 and rxs->rs_datalen = 641. Can't figure out why.

thu-zxs commented 5 years ago

same issue here. When adjusting to a higher rate, I keep getting 3x0x114 CSI value. Not sure what happens.

btw, what is the rate_index_table file you mentioned?

itskalvik commented 5 years ago

When you echo a number into the fixed_rate_idx file you can adjust the MCS rate. 18 gives you MCS 16 at 20MHz and 78 is MCS 16 at 40MHz. you can try playing around with the value to change the Guard interval, MCS rate and channel width.

echo 78 >> /sys/kernel/debug/ieee80211/phy1/rc/fixed_rate_idx

itskalvik commented 5 years ago

Update: It looks like when ever I send packets with any length of payload at MCS 16 or higher at 40MHz, the recv_csi tool receives a fixed payload length of 1924. Not sure why though.

thu-zxs commented 5 years ago

Yeah, right. When echoing 78 into that files, packets with payload length of 1924 keeps occurring, with CSI value being 3x0x114. When value being 77, payload length is 1040, and CSI value is 3x2x114.

MCS 16 corresponds to a 3 streams transmission, which may cause problems according to the author: https://github.com/xieyaxiongfly/Atheros-CSI-Tool-UserSpace-APP/issues/22#issuecomment-287285288

I've sent email to @xieyaxiongfly with no response. Hope anyone could help, really need 3x3x114 CSI.

Update: Question: Is there a link, table or something shows the relationship between the number and guard interval, MCS rate, channel width?

itskalvik commented 5 years ago

I didn't find any reference. Just tried different values. But If I remember it right 0-24 was 20MHz, large GI, after that it was 20 MHz, short GI followed by 40MHz with large and then short GI.

jinzhang-unsw commented 5 years ago

Any updates? I use ubuntu version and any higher than mcs 16 will mostly lose CSI with ampty 3*0*114 and few 3*3*56 ones.

thu-zxs commented 5 years ago

Nothing. Got stuck.

jinzhang-unsw commented 5 years ago

I print out the buffer in csi_fun.c in the receiver, the csi_len variable is wrong, and buf_addr mostly is 0 when transmit in any rates higher than 0x90 (MCS 16). Everything work normally if transmit in rates lower than 0x8f (MCS 15). Potentially the transmitter has bug like bit operation can cause this problem.