# Offest Multiple Access Channel

**URL:** <https://www.ruby-forum.com/t/offest-multiple-access-channel/227969>\
**Category:** GNU Radio\
**Created:** [April 4, 2013, 7:46pm UTC](https://www.ruby-forum.com/t/offest-multiple-access-channel/227969 "2013-04-04T19:46:05Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![Manu\_T\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea5d25/32.png) [@Manu\_T\_S](https://www.ruby-forum.com/u/Manu_T_S)\
**Post date:** [April 4, 2013, 7:46pm UTC](https://www.ruby-forum.com/t/offest-multiple-access-channel/227969/1 "2013-04-04T19:46:05Z")

</div>

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.

---

<div class="post-metadata">

**Author:** ![Manu\_T\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea5d25/32.png) [@Manu\_T\_S](https://www.ruby-forum.com/u/Manu_T_S)\
**Post date:** [April 4, 2013, 8:37pm UTC](https://www.ruby-forum.com/t/offest-multiple-access-channel/227969/2 "2013-04-04T20:37:29Z")

</div>

On Thu, Apr 4, 2013 at 12:45 PM, Manu T S [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) 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](http://gnuradio.org/doc/sphinx/gr/slicedice_blk.html?highlight=interleave#gnuradio.gr.interleave)  
> Available in GRC Stream Conversions\>Interleave

-nw

---

<div class="post-metadata">

**Author:** ![Manu\_T\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea5d25/32.png) [@Manu\_T\_S](https://www.ruby-forum.com/u/Manu_T_S)\
**Post date:** [April 4, 2013, 8:50pm UTC](https://www.ruby-forum.com/t/offest-multiple-access-channel/227969/3 "2013-04-04T20:50:56Z")

</div>

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.

---

<div class="post-metadata">

**Author:** ![Manu\_T\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea5d25/32.png) [@Manu\_T\_S](https://www.ruby-forum.com/u/Manu_T_S)\
**Post date:** [April 4, 2013, 9:11pm UTC](https://www.ruby-forum.com/t/offest-multiple-access-channel/227969/4 "2013-04-04T21:11:23Z")

</div>

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.