[Discuss-gnuradio] tunnel.py doesn't receive packages when transmit and receive frequencies are different

[Weixian Zhou]

I run tunnel.py with two machines and there are some packages exchange immediately after setting the network interface gr0. If I set the frequencies of transmit and receive the same, packages are transmitted and received at both machines:

on machine A:

sudo ./tunnel.py -f 2.4xG ; sudo ifconfig gr0 192.168.200.1 

on machine B:

sudo ./tunnel.py -f 2.4xG ; sudo ifconfig gr0 192.168.200.2

But when I set the frequencies of transmit and receive different under 2.5GHz, packages can't be received at both machines:

on machine A:

sudo ./tunnel.py --tx-freq=2.4xG --rx-freq=2.4yG; sudo ifconfig gr0 192.168.200.1 

on machine B:

sudo ./tunnel.py --tx-freq=2.4yG --rx-freq=2.4xG; sudo ifconfig gr0 192.168.200.2

The wired thing is that when I set the frequencies of transmit and receive different above 2.5GHz, packages can be again transmitted and received:

on machine A:

sudo ./tunnel.py --tx-freq=2.51G --rx-freq=2.512G; sudo ifconfig gr0 192.168.200.1 

on machine B:

sudo ./tunnel.py --tx-freq=2.512G --rx-freq=2.51G; sudo ifconfig gr0 192.168.200.2

I am using USRP N210s and the daughter boards are both XCVR2450. Does anyone can explain why the tunnel.py doesn't receive packages when transmit and receive frequencies are different under 2.5GHz?

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Regards,

Weixian Zhou