Help! offset-QPSK modulation in matlab/simulink...how?

Hello,

I have to design a digital communication-system based on IEEE 802.15.4
(zigbee) in Simulink.

In the following, I will use matlab-syntax.

message='hello'; % source-data
bit=8; % bit-resolution
message_dec=double(message); %convert source-data into ASCII
message_bin=dec2bin(message_dec,bit); %convert ASCII to binary
message_bitstream = reshape(message_bin',1,size(message,2)*bit); % shape
into bitstream

The next procedure is to do the following:

1) Bit to symbol mapping
2) Symbol to chip mapping
3) Offset-QPSK modulation

Regarding 1:

The 4 least significant bits of an octet are mapped into one data-symbol

The 4 most significant bits of an octet are mapped into one data-symbol.

Therefore, there are 16 possible data-symbols

Regarding 2:

Each data-symbol is mapped into a 32 bit PN-sequence (chip-symbol)

Regarding 3:

The PN-sequence is modulated onto a carrier using offset-QPSK.

Can anyone tell me how I do this in Matlab/simulink because I am
totally lost. I have been looking at the OQPSK-block in simulink
but I dont know how to use it correctly. So I thought it would be
easier to make a matlab-file instead.

Any help will be appreciated.

Thanks )



For the interested reader the specification can be found here:

http://kom.aau.dk/~jash02/ieee802-15-4.pdf

 

I'm sure it's very likely someone does, and I'm guessing
that someone could, indeed, tell you.