Now I want to learn the GMSK Modulation and GMSK Demodulation in Gnuradio. Next is a experiment about this. using USRP1 and RFX900 to TX; other USRP1 and DBSRX to RX.
Experiment 1: Data transmission
The files used are benchmark_tx.py and benchmark_rx.py, which are located at gnuradio/gnuradio-examples/pyhton/digital directory. You may refer to the readme file in the same directory for how to run them. Actually, we simply add some codes before send_pkt(eof=True) in benchmark_tx.py to make sure all packets are sent.
Test Result:
The maximum throughput in physical layer is 500Kbps. After removing preamble, header, CRC, etc., the net throughput is about 445kbps. We send 1MByte file (= 8Mbit) data within 18 second. The bottleneck is CPU speed, and a higher CPU speed may achieve 1Mbps.
To measure the pack error rate (PER), we set the packet length as 1500 bytes, and PER is about 0.1% with default transmit power, which can be adjust dynamically. Since in our test, we only use CRC, the PER can be improved by using FEC.
In this experiment, we test data transmission between two USRP. First, input benchmark_rx python file with proper parameters setting
(./benchmark_rx.py –f 900M)
in receiver side. Then, input benchmark_tx python file with proper parameters setting (./benchmark_tx.py –f 900M)
in transmitter side. You will see the data transmission with packet number and CRC result output from the command line.
some picture about this Experiment .
Reporter:Nick
Chan