Re: [Discuss-gnuradio] BPSK output abnormal

[Surya Agam]

Oh sorry I forgot to reply to all.

Now there's a new problem. I use Packet Encoder to add preamble, the setting is:

Encoder

- sps = 2

- bps = 1 (bpsk)

- preamble = 1010010011110010

- access code = 1010110011011101101001001110001011110010100011000010000011111100

- pad for USRP = no

- payload strength = 16

Decoder

- access code = 1010110011011101101001001110001011110010100011000010000011111100

- threshold = -1

both access code and preamble are from http://gnuradio.org/doc/sphinx-3.7.2/digital/pkt_utils.html

The output now become 0kB

On Mon, May 25, 2015 at 10:09 PM, Tom Rondeau <address@hidden> wrote:

On Sun, May 24, 2015 at 4:25 PM, Surya Agam <address@hidden> wrote:

Oh thank you Tom, I can recover the file size. About frame synchronization, am I need Polyphase Clock Sync Block? And also I have no idea about "You can zero-pad the input to "push" the samples through."?

(please keep emails on the mailing list)

The PFB clock sync handles symbol synchronization -- it finds where the bits are. You'll need another level of synchronization to find the start of the frame, usually by looking for a known start pattern, preamble, etc.

And there are many ways to accomplish the zero-padding. I'll leave that up to you to figure out :)

Tom

 

On Mon, May 25, 2015 at 12:34 AM, Tom Rondeau <address@hidden> wrote:

On Sun, May 24, 2015 at 4:54 AM, Surya Agam <address@hidden> wrote:

Hi everyone,

I try to simulate file transfer using BPSK with block diagram

File Source --> PSK Mod --> PSK Demod --> File Sink

The block setting is

File Source :

-file type = .jpg (282,8 kB (282.765 bytes))

-repeat = no

-vec length = 1

PSK Mod :

-num of constellation = 2

-gray code = yes

-diff. encoding = yes

-sample/symbol = 2

-excess BW = 0.35

-verbose = off

=log = off

PSK Demod :

-num of constellation = 2

-diff. encoding = yes

-sample/symbol = 2

-excess BW = 0.35

-frequency BW = 6.28/100.0

-timing BW = 6.28/100.0

-phase BW = 6.28/100.0

-gray code = yes

-verbose = off

-log = off

File Sink

-vec length = 1

-unbuffered = on

-append file = overwrite

The size of input file = 282,8 kB (282.765 bytes)

but the size of output file = 2,3 MB (2.262.066 bytes)

What's wrong with my fg?

Thank you,

Surya Agam

The output is unpacked. So each sample only represents a single bit. You have to repack them into 8 bits per byte, but you'll also need to know where to start through some kind of frame synchronization.

282765*8 = 2262120

The rest of the difference is due to delays in the filters. You can zero-pad the input to "push" the samples through.

Tom