Hello, all!!!
I have a question of measuring RSSI on the USRP board. I searched the
answer throughout the mailing list and I only found out three ways:
- Analog RSSI (we can read it using AUX ADC)
- Digital RSSI in FPGA (from output of ADCs)
- Digital RSSI in host (computed however you like, from the channel zed
signal sent over the bus by the USRP)
Here, I usedv = u.read_aux_adc(0, 0) to read RSSI whenever there is a
packet received, and then I average the whole RSSI values of 3000
packets I received. Below are the data I got: the working condition is
bitrate=2Mbps, modulation = dqpsk, the demo file i was using are
benchmark_tx.py and benchmark_rx.py under
gnuradio-examples/python/digital
–tx-amplitude -s PER Rssi
100 100 60.30% 168
250 100 47% 170
500 100 40% 177
1000 100 39% 248
1500 100 40% 819
2000 100 40.2% 19372
50 50 25.09% 169.2084
500 50 25.06% 173.0687
1000 50 22.24% 215.4980
1500 50 22.05% 651.8132
2000 50 23.30% 1138.7028
4000 50 23.40% 1721.1643
250 40 21.30% 168.2404
500 40 19.34% 172.1490
1000 40 18.15% 208.2196
1500 40 18.72% 462.1265
My question is what these digital numbers stand for!!! e.g. if it is
168, how much is the actual RSSI value in dB?
it is a wireless communication with two USRPs standing 0.4 meters apart
from each other. Why does the RSSI increase so nonlinearly when the
tx-amplitude increases linearly or regularly?
Matt told us that the RSSI measures the analog signal level after the
lowpass filters on the board and these filters are about 15-20 MHz wide.
So, how can I narrow the bandwidth of those lowpass filters using
software to get it fit into my intrested area? Is there a way out? Any
help will be very useful to us! Thanks a lot for all!
Bill