A cooperative diversity transmission scheme using random unitary matrix modulation(RU-CD)is presented to focus on the problem that the combination of maximum-ratio combining(MRC)and distributed space-time coding(MRC-DSTC)scheme has zero matrices in the processing matrix. The new scheme processes received signals at relay antennas by the random unitary matrix
and the orthogonal spreading codes are used to linearly combine the signals of the time-slots. Then the conjugate processing is performed so that the signals of the relay are transported in only two time-slots. The signals are decoded at destination nodes using the properties of the complex signals. The real and imaginary parts of the transmit signals are decoded independently such that the decoding complexity is reduced. Simulation results and comparisons with the MRC-DSTC scheme show that the bit error rate of the RU-CD scheme reduces about 3 dB and 5 dB
respectively
in the cases that there exist one or two relay nodes in the system.
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references
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