How can i use the Offset 16QAM or Offset 64 QAM in communication toolbox - Matlab 2015b.

2015 10 21
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更新时间：2017 4 19
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I am using toolbox communication of Matlab 2015b version. How can i use Offset 16QAM or Offset 64 QAM in this toolbox? There is only OQPSK (comm.OQPSKModulator). Thank you in advanced.

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Mike McLernon
Mike McLernon 2015-11-9

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You can build up the offset QAM transmitter by doing the following:
  1. Create the 16QAM or 64QAM signal with the Rectangular QAM Modulator Baseband block (in Simulink) or the comm.RectangularQAMModulator System object (in MATLAB).
  2. Filter the signal with an appropriate pulse shaping filter -- a raised cosine filter would be a common choice. Interpolate by 4, 8, or some other even number.
  3. Manually delay the quadrature channel of the QAM signal by half of the interpolation factor.

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Hase
Hase 2015-11-9
编辑：Hase 2015-11-9
Hi Mr. Mike McLernon,
Thank you very much for your great support. I do step by step instructions but the constellation is incorrect. Maybe i compose the Matlab code is not properly. Could you help me to check it?
Thank you very much.
Van.
%%% Here is Matlab code for 16 OQAM %%
M = 16; % Modulation order
k = log2(M); % Bits/symbol
n = 2000; % Transmitted bits nSamp = 8; % Samples per symbol, Interpolate factor
EbNo = 10; % Eb/No (dB)
hMod = comm.RectangularQAMModulator(M,'BitInput',true);
span = 10; % Filter span in symbols
rolloff = 0.25; % Rolloff factor
hTxFilter = comm.RaisedCosineTransmitFilter('RolloffFactor',rolloff, ... 'FilterSpanInSymbols',span,'OutputSamplesPerSymbol',nSamp);
fvtool(hTxFilter,'impulse');
x = randi([0 1],n,1); % data binary
modSig = step(hMod,x); % 16 QAM symbol
txSig = step(hTxFilter,modSig); % apply the RC filter with nSamp = 4
hdelay = dsp.Delay(nSamp/2); % delay object
q_channel = step(hdelay,imag(txSig)); % delay Q channel by nSamp/2 oqam_sig = real(txSig) + 1i*q_channel; % 16 OQAM signal
scatterplot(txSig); scatterplot(oqam_sig);

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