Benchmark_rx is giving weird output for high bit rate


This is Nazmul, a PhD student of Rutgers University. I am using a
form of ‘’ and ‘’ for my research. I am
transmitting a random binary sequence from an USRP2 testbed and
the bit error rate at the receiver (BER), another USRP2 testbed.
I am generating a long binary sequence, grouping them into different
and then transmitting the packets using ‘benchmark_Tx’ program. I
the packets using ‘’ and then find the BER.

The program works well when bit rate is lower than 3 Mbps or 3.5 Mpbs.
However, when the bit rate exceeds 3.5 Mbps, the benchmark_Rx produces a
bunch of S characters. It produces a weird output like following!!


I don’t know why this weird output occurs. Does it happen because I am
exceeding the “capacity” of the path? Or is there an in built low pass
filter at the receiver that only passes signals whose bandwidth is lower
than 3 MHz? (let’s say that I am using Differential BPSK here).

Your feedback on this will be highly appreciated.



Muhammad Nazmul I.

Graduate Student
Electrical & Computer Engineering
Wireless Information & Networking Laboratory
Rutgers, USA.