On Fri, Feb 15, 2013 at 9:46 PM, Manu T S <[email protected]> wrote:
> Hi, > > I was running the benchmark scripts with the following set of parametrs > > -f 915M -r 5000000 -m psk -8 > > with 30 dB gain set on both Tx and Rx. I was getting cluttered overflows > and packet received during that time are in error.. Like I'm receiving > about a 1000 packet without error and then then system runs into overflow > and about then quite a large number of packets are received in error. > > Output is posted > > Demodulator: > bits per symbol: 3 > RRC roll-off factor: 0.35 > FLL bandwidth: 6.28e-02 > Timing bandwidth: 6.28e-02 > Phase bandwidth: 6.28e-02 > -- Opening a USRP2/N-Series device... > -- Current recv frame size: 1472 bytes > -- Current send frame size: 1472 bytes > > UHD Receiver: > UHD Args: > Freq: 915MHz > Gain: 30.000000 dB > Sample Rate: 3.33333Msps > Antenna: None > Spec: None > > Demodulator: > bits per symbol: 3 > RRC roll-off factor: 0.35 > FLL bandwidth: 6.28e-02 > Timing bandwidth: 6.28e-02 > Phase bandwidth: 6.28e-02 > > Receive Path: > modulation: psk_demod > bitrate: 5Mb/s > samples/symbol: 2.0000 > Differential: True > Using Volk machine: avx_64_mmx > ok = True pktno = 1 n_rcvd = 1 n_right = 1 > ok = True pktno = 2 n_rcvd = 2 n_right = 2 > ok = True pktno = 3 n_rcvd = 3 n_right = 3 > . > . > . > ok = True pktno = 2953 n_rcvd = 2953 n_right = 2953 > ok = True pktno = 2954 n_rcvd = 2954 n_right = 2954 > ok = True pktno = 2955 n_rcvd = 2955 n_right = 2955 > ok = True pktno = 2956 n_rcvd = 2956 n_right = 2956 > ok = False pktno = 2957 n_rcvd = 2957 n_right = 2956 > ok = False pktno = 2959 n_rcvd = 2958 n_right = 2956 > ok = False pktno = 2961 n_rcvd = 2959 n_right = 2956 > ok = False pktno = 2963 n_rcvd = 2960 n_right = 2956 > ok = False pktno = 2965 n_rcvd = 2961 n_right = 2956 > ok = False pktno = 2967 n_rcvd = 2962 n_right = 2956 > . > . > . > ok = False pktno = 3838 n_rcvd = 3369 n_right = 2956 > ok = False pktno = 3841 n_rcvd = 3370 n_right = 2956 > ok = False pktno = 3843 n_rcvd = 3371 n_right = 2956 > ok = True pktno = 3845 n_rcvd = 3372 n_right = 2957 > ok = True pktno = 3846 n_rcvd = 3373 n_right = 2958 > ok = True pktno = 3847 n_rcvd = 3374 n_right = 2959 > ok = True pktno = 3848 n_rcvd = 3375 n_right = 2960 > . > . > . > > > Any idea how to avoid these overflows??? > -- > Manu T S > This is usually a problem due to the receiver not being able to keep up with the flow of samples from the UHD device. Try running at a lower bitrate. If you're seeing overflows temporarily and then things are correcting themselves, it looks like you might be right on the edge of your system's capabilities. In this case, it's like some other process/task is taking some time away from your app, causing it to slow down just enough to cause problems, but then things look like they come back. You could also try to run with realtime privileges enabled to make sure your process gets priority. On the other hand, the output you show here doesn't have any overflow indication. Are you sure that this is what's happening? You're running at 915 MHz, the center of the 900 MHz ISM band (depending on where you are). It's likely to have other signals in it. Maybe this is just a case of interference? Tom
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