The Simple Near-Optimal Pairing Scheme of Superposition Coding in Downlink DS-CDMA Multi-path Channel

The paring scheme of superposition coding (SC) is developed to increase the user capacity in downlink DS-CDMA on multi-path channel. Unlike the previous work on frequency flat fading channel, the inter-user interference in the same SC and interference from other orthogonal codes are considered in selecting a pair of users for SC and evaluating their power allocation. We first examine the maximum supportable signal to interference and noise power ratio (SINR) and introduce the simple pairing scheme which offers nearly the same capacity with the same transmit power as the optimum pairing but requires far less computational complexity.