no data packet, just ack packets

[kebZhang]

Dear bastibl,

I use a wifi to perform as AP, a PC as a client. And I use iperf to communicate between AP and client. Then I use usrp and wifi_rx.grc to receive data. But in wireshark, it can just capture ack packets and some broadcast packets, there is no data packet in wireshark list.

I use another pc to run wireshark, and it can actually capture data packet.

I run wifi_rx.grc on ubuntu 20.04lts, and I use maint-3.10 gr-ieee802-11.

So could you give me some advice?

[bastibl]

The AP might use a different MCS for the data, which requires a better SNR (-> try to improve signal quality). Or the GNU Radio receiver only receives frames up to 1500 byte, maybe the data frames are larger (-> change constants in the code). Or the devices use non-11a/g for the data communication (i.e., larger bandwidths, MIMO, etc) (-> this doesn't work with this module). I'd guess it's the latter. In that case, you'd have to force 11a/g mode.

[kebZhang]

Thank you for your reply.

I use openwifi as AP, and use a PC as client. I run iperf3 server on openwifi and iperf3 client on PC to continue tcp connection. in AP iperf3 -s in client ./iperf3.exe -c 192.168.10.122 -t 1200 -l 1200 I can see data packet in wireshark of PC.

I have looked through the config of openwifi and make sure that I have set 11a mode in channel 48 and bandwidth is 20Mhz.

I change #define MAX_PAYLOAD_SIZE 1800in util.h and recompile the project. I also change the MTU size to 1300. But when I run wifi_rx.grc with usrp B210. I still can only get ack packets and beacon packets in wireshark wifi.pcap.

[bastibl]

you could try changing the role of openwifi and the PC, i.e., run iperf -s on the PC. Also you could use a normal WLAN card in monitor mode to see what packets are sent. If the frames are too large, just change the MTU of the network interface.