Thanks for your prompt response! I have tried connecting the wifi_tx and wifi_rx in loopback configuration. At 10Packets/s, it would give me a lot of "Warning: starting to receive new frame before old frame was complete" messages. So quite a lot of packets didn't reach the MAC decoding stage. To eliminate the above warning completely, I had to increase the interval to 20s. But then these sequence numbers have correct checksum values. There is no under/overflow at the tx/rx in this configuration.I believe this channel to be quite clean, I checked with the IT department of my institute and also listened to the channel using a spectrum analyzer. Even if it weren't, you are right that it shouldn't mess up the same sequence numbers every time. Is there something else I could look into?
Bests, Nikita On Fri, Jan 13, 2017 at 8:30 PM, Bastian Bloessl <bloe...@ccs-labs.org> wrote: > Hi, > > On 01/13/2017 11:17 AM, Nikita Airee wrote: > > Hi everyone! > > > > * Ubuntu 14.04 > > * Gnuradio version : 3.7.10.1, UHD_3.11.0.git-28-gc66cb1ba > > * 2 USRP 2953R(x310 + cbx40) connected to host laptops using pcie > > cable, antennae=vert2450 > > * center frequency=2.484GHz, samp_rate=10MHz > > > > I have been transmitting at the rate of 10 Packets/s over wireless link > > with distance between the tx and rx 3m and 6m. tx_gain is set to 30dB > > and rx_gain to 0. (I have varied these gains to find no improvement). > > I get a constant total frame error rate at the receiver ~10% for a > > payload of size 50 bytes. The problem is that the frames for which the > > checksum fails are always the same sequence > > numbers(10,12,31,39,49,58,89,93,94,95...). > > I have tried the different channel estimation algorithms and tried > > sending the same packet(seq number 0) over and over but still the same > > numbers are are dropped. I have also increased the interval between > > transmission to no affect. > > really strange that always the same frames are lost. Can you run the > flow graph in loopback mode without any hardware (i.e., connect RX to TX > in GRC), just to rule out any software issues. > > Also assert that there are no overruns (in the receiver) and no > underruns (in the transmitter). > > There could also be interference on 2.4GHz, but very unlikely that it > always hits the same frames. I assume you are sending frames that don't > trigger any response from APs (or other nodes that might be in radio > range). > > Best, > Bastian >
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