Offest Multiple Access Channel

GNU Radio
1

Hi Everyone,

I need help regarding a problem.

It’s a Multiple Access Channel problem but one of the source is offset
by
half a symbol period.

########################################################
source1 —> bytes_to_chunks(1) ----> chunks_to_symbol —

|

—> black_box —>

|
source2 —> bytes_to_chunks(1) ----> chunks_to_symbol —
########################################################

I want to add these to outputs such that the the symbol corresponding to
souce2 falls between two symbols of source1.

There will be RRC waveform corresponding to every bit out of the source.
The RRC waveform corresponding to a bit in source2 should fall between
RRC
waveform corresponding to 2 bits of source1 ( preferably at the midpoint
).

I guess I can not do a streams to stream converter, before RRC, because
what that would give me a channel with twice the bandwidth of a single
channel.

Should I work on a new RRC filter block with 2 inputs or is there any
other
way to do this?

New ideas to achieve this is also welcome.

2

On Thu, Apr 4, 2013 at 12:45 PM, Manu T S [email protected] wrote:

|
There will be RRC waveform corresponding to every bit out of the source.
New ideas to achieve this is also welcome.

–
Manu T S

Unless I’m misunderstanding it sounds like you want to interleave bytes.
http://gnuradio.org/doc/sphinx/gr/slicedice_blk.html?highlight=interleave#gnuradio.gr.interleave
Available in GRC Stream Conversions>Interleave

-nw

3

Hi Nathan,

Thanks for the tip
I’m not sure if its same as interleaving.
Suppose I have W bandwidth, and I interleave bits of two sources. I
guess
we only get effective W/2 bandwidth per source.

4

Sorry to bother the forum.

I have made a .grc(attached) which gives me the same result.

Of course, I have to design a receiver for this MAC, and I’m stumbling
in
dark.