On Tue, Apr 19, 2011 at 10:04 PM, Fengyuan Gong <[email protected]>wrote:
> Hi, All, > > I want to run benchmark_tx.py and benchmark_rx.py simultaneously. So I > write a shell script to do that. > #-----------------------run.sh------------------------------- > sudo ./benchmark_tx.py -f 24e8 -w 0 & > sudo ./benchmark_rx.py -f 24e8 -w 1 & > > From the output result, sometimes, the first output message from the > receiver is: > .ok = True pktno = 0 > it means the first packet that receiver could get, is the first > transmitted packet. > But sometimes, the first output message from the receiver is: > .ok = True pktno = 2 > it means the first packet that receiver could get, is only the second > transmitted packet. > Then I run "sudo ./run.sh" again, > .ok = True pktno = 1 > > It seems like the first received packet number is random. It may be 0, > or 1, or 2. After receiving the first packet, the following received > packet will all be correct. > So the receiver will miss the first or second transmitted packets if I > run benchmark_tx.py and benchmark_rx.py simultaneously. > > Has anyone seen the same case before? Why will the receiver lose the > first one or two packets? > > -- > Best Regards~ > Fengyuan Gong > There is a lock-in time associated with all of the synchronization loops, which will change depending on the noise in the system. So it might not synchronize until after the first packet or so. So yes, it's random because you're dealing with stochastic processes :) I'm a bit surprised that you are sometimes missing the first 2 packets. Could be due to bad multipath (the benchmark scripts don't use an equalizer) or any of the other random things that happen. Tom
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