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Help! offset-QPSK modulation in matlab/

Discussion in 'General Electronics' started by bamse, Feb 28, 2004.

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  1. bamse

    bamse Guest


    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 :eek:)

    For the interested reader the specification can be found here:
  2. Rich Grise

    Rich Grise Guest

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

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