Hi All:
I am new to GNU Radio and I am experiencing a few anomalies. My experimental setup is as follows:
- I am using USPR2 with GNU Radio ver. 3.2 installed on an Intel 64-bit Quad Core machine with GigEthernet.
- I
am using XCVR2450 daughter card and the latest firmware on the USRP2s.
- I am running benchmark_rx.py and benchmark_tx.py using two USPR2s.
- I have wired the two USRPs using a 60 dB attenuator.
My Observations:
- The
maximum bit rate I could achieve was 12.5 Mbps corresponding to
samples/symbol = 2 and interpolation and decimation factor set to 4
- The minimum bit rate I could see was 120 Kbps in the 2.4GHz band and 250 Kbps on the 5GHz band.
I have the following questions:
1. What is the minimum and maximum bit rates that USPR2 can support ?
My immediate guess for minimum bitrate is that it depends on the ADC/DAC sampling rates,
samples/symbol and interpolation and decimation factor. So with least interpolation (4) and least Samples/Sym (2), the calculations give 12.5 Mbps (for GMSK - 1bit/sample/Hz).
The maximum bit rate is limited by the host processor; whether it can churn out as many packets as the USPR2 wants in a second.
Is my analysis correct ?
2. Why does the minimum bit rate depend on the carrier frequency ?
I tried changing the Tx amplitude and Tx gain at 5G but it still didn't change anything.
3.
How to perform benchmark_rx/tx in BERT mode ( from digital-bert folder)
? Looks like the scripts are written for USRP1. How to modify them to
make it work on USRP2 ?
Can anyone please help me resolve these issues ?
Thanks,
Srinivas
Graduate Student,
WINLAB, Rutgers University, NJ