I have two USRP N210 devices connected by an attenuator cable. I set up the following experiments.
-- BEGIN EXPERIMENT 1
Step 1) Use benchmark_tx on one of the USRPs and send 100 packets. At the receiver, I simply record the incoming samples and save them into a file called samples1.dat. This file is static and does not change from now on.
Step 2) Run benchmark_rx with the --from-file=samples1.dat option. The other parameters (modulation, fft-length, occupied-tones, etc) are identical to those I used at the transmitter in Step 1. Measure the packet delivery rate.
Step 3) Repeat Step 2 a bunch of times. Sometimes, I notice differences in the packet delivery ratios, even though all runs of the experiment use the identical 'samples1.dat' file and an identical set of parameters These differences are small (1-2 packet difference), but I don't understand why they exist.
Is this normal behavior? If so, could someone please let me know what the probable causes are?
-- END EXPERIMENT 1
The next experiment does not use either of the USRP devices.
-- BEGIN EXPERIMENT 2
1) Use benchmark_tx to generate 100 packets, and write the samples into a file (samples2.dat) using the --to-file option.
2) Use benchmark_rx with the --from-file=samples2.dat option and check the packet delivery rate. The parameters used (fft-length, etc) are obviously identical to those used to generate the samples in Step 1. I observe that the delivery rate is never even close to 100%.
3) Change to a different parameter set and repeat steps 1 and 2. Across different runs, I observe that the delivery rate is anywhere between 30% and 85%.
This cannot be the expected behavior. Any pointers on what I'm doing wrong would be much appreciated!
-- END EXPERIMENT 2