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[Discuss-gnuradio] Repeatability of delivery ratios using benchmark_tx/r


From: Aditya Dhananjay
Subject: [Discuss-gnuradio] Repeatability of delivery ratios using benchmark_tx/rx
Date: Wed, 16 Oct 2013 22:22:04 -0400

Hi All,

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

Thanks!

Aditya

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