[Discuss-gnuradio] No Packet Reception for benchmark_rx and No PINGing for tunnel.py

[Ahmed Majeed Khan]

Hi,
I completed the installations and checked tone generation and benchmark_tx/rx over a pair of usrp, along with usrp_wfm_rcv.py for or FM reception. These examles ran pretty fine. Then I tried tunnel.py with command line arguments as in README file:

./tunnel.py -f 423.0M --bitrate=500k

The output was a series of 'B', stating no carrier sensing.

I reduced the carrier freauency to 10 M and tried running it again. This time, there was no 'B' sequence and the output of first machine was:

>>>gr_fir_fff
modulation: gmsk
frequency: 10M
bitrate: 500kb/sec
sample/symbol: 2
Carrier Sense Threshold: 30dB
Allocated Virtual Network Interface: gr0

Then, after ifconfig on another terminal window, first window showed:

Tx: len(payload) =  90
Tx: len(payload) =  54
Rx: ok = false  len(payload) = 90 
Tx: len(payload) =  289
Tx: len(payload) =  193
Tx: len(payload) =  289
Tx: len(payload) =  78
Tx: len(payload) =  289
Tx: len(payload) =  265
Rx: ok = false  len(payload) = 265

and so on..........

The output of the second machine was identical, except there was NO "Rx: ok = true/false  len(payload) = xx" in that.

When I pinged one machine with other, the following error message appeared:
PING 192.168.200.1 (192.168.200.1) 56(84) bytes of data
>From 192.168.200.2 icmp_seq=1 Destination Host Unreachable
(Till icmp_seq=32, when I disconnected).

After that, I am able to run usrp_wfm_rcv.py, but when I again ran benchmark_rx.py and benchmark_tx.py, following is the output with NO packet reception: 
(Please note, earlier I used same command line arguments and got some packets received)

I call benchmark_rx on my usrp and leave it running,

$ python ./benchmark_rx.py -f 10M -R A --rx-gain=70 -v -r 500K

bits per symbol = 1
M&M clock recovery omega = 2.000000
M&M clock recovery gain mu = 0.175000
M&M clock recovery mu = 0.500000
M&M clock recovery omega rel. limit = 0.005000
frequency error = 0.000000

Receive Path:
Using RX d'board A: Basic Rx
Rx gain:         70
modulation:      gmsk_demod
bitrate:         250kb/s
samples/symbol:    2
decim:           128
Rx Frequency:    10M


I then call benchmark_tx on my second usrp,

$ python ./benchmark_tx.py -TA -f 10M -r 500k -v --tx-amplitude=20000

>>> gr_fir_fff: using SSE
bits per symbol = 1
Gaussian filter bt = 0.35
Using TX d'board A: Basic Tx
Tx amplitude     20000.0
modulation:      gmsk_mod
bitrate:         500kb/s
samples/symbol:    2
interp:          128
Tx Frequency:    10M

This shows packets are apparently being transmitted. However when I checked the console of second machine for benchmark_rx, no packet notifications are being displayed.

My Questions:
1- Is the USRP transmitting data? 
2- Why is it not receiving this data if it is transmitting?
3- Do 'Carrier Sensing' has something to do with frequency, in tunnel.py?

-Ahmed