On 11/7/07, Marko Simunac <[EMAIL PROTECTED]> wrote: > ...and am assigning a carrier treshold of 90(-c 90) to get rid the BBBBBBs. > Can someone help me to increase the distance between the two USRPs, and > theoretically what is the max distance between the two USRPs that tunnel can > work?
This carrier threshold is probably too high. There is a sweet spot for this parameter, only determined by experiment. If it is too low, then the nodes won't transmit due to it thinking background noise is someone transmitting (those are the BBBs you're getting rid of.) If it is too high, the nodes will "ignore" anyone else transmitting, resulting in continuous collisions, and no actual data flow. In my experience, a properly tuned carrier threshold results in one or two Bs per transmitted packet on each side of a two node network, when sending full duplex traffic. The other knob to adjust is the receiver gain. Depending on your antenna, you need to adjust this for maximum signal to noise ratio. But changing your gain changes your required carrier sense threshold as well. As Eric mentioned, a good way to judge this is to run the benchmark_tx.py script on one node, then use the usrp_fft.py script on the other to see the transmitted waveform. You can adjust the gain slider up and down to get the widest spread between the noise floor and the received signal peak. Then use this same gain in the tunnel.py script. Now you can adjust the carrier sense threshold to be just high enough to be able to transmit with nothing being transmitted from the other end. All this /should/ be automated... -- Johnathan Corgan Corgan Enterprises LLC http://corganenterprises.com/ _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
