Then you really want some pulse shaping filter, like the RRC that is used by default.
On 06/23/2015 05:39 PM, Surya Agam wrote: > My target is using USRP, but still simulate using a noise channel. The > output of PSK Demod is bit "0" a with some "1" and no input data in > the output. > > I attach the input and the output screenshot. > > On Tue, Jun 23, 2015 at 10:12 PM, Nowlan, Sean > <[email protected] <mailto:[email protected]>> wrote: > > 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:[email protected] > <mailto:[email protected]>] > *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 > <[email protected] <mailto:[email protected]>> > 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:*[email protected] > <mailto:[email protected]> > [mailto:discuss-gnuradio-bounces+sean.nowlan > > <mailto:discuss-gnuradio-bounces%2Bsean.nowlan>[email protected] > <mailto:[email protected]>] *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 > > > > > -- > Sincerely, > > Surya Agam > University Al Azhar of Indonesia, Jakarta > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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