A multi-stage multi-user decode-and-forward cooperative communications scheme using linear combination

Wireless network cocast (WNC) offers a better tradeoff in spatial diversity and transmission delay than the immediate-neighbor cooperation (INC) and the maximal cooperation (MAX) [1]. However, its transmission delay is almost double that of direct transmission (DTX), resulting in a long waiting time for the destination to detect all user signals. Furthermore, cooperation probability
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is low, eventually reducing the spatial diversity order at the destination. This paper solves the above problems by allowing users to linearly combine their own signals with successfully detected partner signals and to perform a simple multi-user detection. Closed-form error performance formulas are derived and validated by computer simulations. Results show that, for low cross-correlation among user signature waveforms, the proposed scheme offers a better performance than WNC and achieves the same transmission delay as DTX. For high cross-correlation, its performance is negligibly degraded as compared to WNC.