This depends on your setup. If you’re just simulating with PSK Mod --> PSK Demod and then comparing the input with the output, then you may be seeing some initial output from the filters due to the convolution operations. Try searching through your output after some delay.
If you disabled differential encoding, you may be seeing a bitstream that is not correct due to phase locking with a fixed phase offset at the receiver. If you’re going over hardware or through a noise channel, you might not have enough SNR to decode properly. If you’re using USRPs, have you experimented with the benchmark_tx/rx scripts? These implement various types of single carrier modulation, including many variants of PSK. Sean From: Surya Agam [mailto:surya11.01a...@gmail.com] Sent: Tuesday, June 23, 2015 10:53 AM To: Nowlan, Sean Cc: GNURadio Discussion List Subject: Re: [Discuss-gnuradio] PSK Mod Block Thank you for the fast respond, But, when I use PSK Mod then PSK Demod the output different from the input so no output from the Packet Decoder. Any suggestion? On Tue, Jun 23, 2015 at 9:17 PM, Nowlan, Sean <sean.now...@gtri.gatech.edu<mailto:sean.now...@gtri.gatech.edu>> wrote: Introducing ISI to a PSK signal with a root-raised cosine (RRC) filter is a standard communications technique. At the receiver, use a matched RRC filter to eliminate the intentional ISI introduced at the transmitter. This works because the combined filter response of the two filters is a raised cosine pulse, which satisfies the Nyquist criterion for zero ISI. In the PSK Mod block, the filter construction is not exposed to the user except through the excess bandwidth or roll-off parameter. You could adjust that bandwidth factor to be close to zero, but this will create a very long filter. If you really want to do what you are saying, it would be worth looking at the source code for the PSK Mod block, and taking the filter out. However, it is likely that you don’t really want to do this. Sean From: discuss-gnuradio-bounces+sean.nowlan=gtri.gatech....@gnu.org<mailto:gtri.gatech....@gnu.org> [mailto:discuss-gnuradio-bounces+sean.nowlan<mailto:discuss-gnuradio-bounces%2Bsean.nowlan>=gtri.gatech....@gnu.org<mailto:gtri.gatech....@gnu.org>] On Behalf Of Surya Agam Sent: Tuesday, June 23, 2015 9:47 AM To: GNURadio Discussion List Subject: [Discuss-gnuradio] PSK Mod Block Hello, I wanna use PSK Mod Block, but the ISI is annoying. Why PSK Mod Block have a it's own ISI? And also is there anyway to disable the ISI from the block? -- Sincerely, Surya Agam University Al Azhar of Indonesia, Jakarta -- Sincerely, Surya Agam University Al Azhar of Indonesia, Jakarta
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