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 A.
University Al Azhar of Indonesia, Jakarta

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]n.invalid
[mailto:[email protected]n.invalid] On
Behalf Of Surya A.
Sent: Tuesday, June 23, 2015 9:47 AM
To: GNURadio D.ion 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 A.
University Al Azhar of Indonesia, Jakarta

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]
wrote:

that bandwidth factor to be close to zero, but this will create a very long
From: [email protected]n.invalid

Sincerely,

Surya A.

University Al Azhar of Indonesia, Jakarta


Sincerely,

Surya A.
University Al Azhar of Indonesia, Jakarta

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 A. [mailto:[email protected]]
Sent: Tuesday, June 23, 2015 10:53 AM
To: Nowlan, Sean
Cc: GNURadio D.ion 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]n.invalidmailto:[email protected]
[mailto:discuss-gnuradio-bounces+sean.nowlanmailto:discuss-gnuradio-bounces%2Bsean.nowlan[email protected]mailto:[email protected]]
On Behalf Of Surya A.
Sent: Tuesday, June 23, 2015 9:47 AM
To: GNURadio D.ion 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 A.
University Al Azhar of Indonesia, Jakarta


Sincerely,

Surya A.
University Al Azhar of Indonesia, Jakarta

Then you really want some pulse shaping filter, like the RRC that is
used by default.

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]
wrote:

Subject: Re: [Discuss-gnuradio] PSK Mod Block

Sean

Surya A.

University Al Azhar of Indonesia, Jakarta


Sincerely,

Surya A.
University Al Azhar of Indonesia, Jakarta

So,
“it appears that PSK Mod expects packed bytes” = from Packet Encoder
direct
to PSK Mod
“the Demod block outputs a stream of bits with 1 meaningful bit in the
LSB
position” = Repack Bits 1 to 8 (packet alignment = input)
the result, without delay the output is similar but not same. I don’t
know
if need a long delay (the input and output from attachment not from the
same packet) or I use a wrong Repack Bits block setting.

On Tue, Jun 23, 2015 at 11:51 PM, Nowlan, Sean
[email protected]
wrote:

packed symbols. Symbols are grouped from MSB to LSB.”
Behalf Of *Marcus Müller
On 06/23/2015 05:39 PM, Surya A. wrote:

If you disabled differential encoding, you may be seeing a bitstream that
If you’re using USRPs, have you experimented with the benchmark_tx/rx
Sent: Tuesday, June 23, 2015 10:53 AM
But, when I use PSK Mod then PSK Demod the output different from the input
works because the combined filter response of the two filters is a raised

To: GNURadio D.ion List

Surya A.


Sincerely,

Surya A.
University Al Azhar of Indonesia, Jakarta

Looking quickly at the documentation, for PSK Mod and Demod blocks, it
appears that PSK Mod expects packed bytes (8 bits of meaningful data in
each byte) and that the Demod block outputs a stream of bits with 1
meaningful bit in the LSB position. Use a Repack Bits block. However,
you may need to play with the delay (insert a Delay Block) to make sure
that the Repack Bits block is aligning bits into bytes properly.

Mod: “The input is a byte stream (unsigned char), treated as a series of
packed symbols. Symbols are grouped from MSB to LSB.”

Demod: “The output is a stream of bytes, each representing a recovered
bit. The most significant bit is reported first.”

From: [email protected]n.invalid
[mailto:[email protected]n.invalid] On
Behalf Of Marcus M.
Sent: Tuesday, June 23, 2015 11:59 AM
To: [email protected]
Subject: Re: [Discuss-gnuradio] PSK Mod Block

Then you really want some pulse shaping filter, like the RRC that is
used by default.
On 06/23/2015 05:39 PM, Surya A. 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 A.
[mailto:[email protected]mailto:[email protected]]
Sent: Tuesday, June 23, 2015 10:53 AM
To: Nowlan, Sean
Cc: GNURadio D.ion 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]n.invalidmailto:[email protected]
[mailto:discuss-gnuradio-bounces+sean.nowlanmailto:discuss-gnuradio-bounces%2Bsean.nowlan[email protected]mailto:[email protected]]
On Behalf Of Surya A.
Sent: Tuesday, June 23, 2015 9:47 AM
To: GNURadio D.ion 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 A.
University Al Azhar of Indonesia, Jakarta


Sincerely,

Surya A.
University Al Azhar of Indonesia, Jakarta


Sincerely,

Surya A.
University Al Azhar of Indonesia, Jakarta


Discuss-gnuradio mailing list

removed_ema[email protected]mailto:[email protected]

https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs