Near-Far Resistance of Multicarrier CDMA Systems.

摘要

Multicarrier (MG) CDMA systems have been developed and rapidly gained popularity as they capitalize on both MCM (multicarrier modulation)'s resilience to MUI and direct-sequence (DS) CDMA's robustness against frequency selectivity to mitigate both MUI and the inter-symbol interference (ISI) caused by time dispersive channels. However, the well-known near-far problem in a multiuser setting still places fundamental limitations on the performance of MC-CDMA communication systems, and this issue has been considered by very few papers. In this paper the theoretical near far resistance of the MMSE detector in the uplink MC-CDMA (with and without cyclic prefix (CP)) setting is derived. It turns out that the near-far resistance of MC-CDMA without CP has the same form as that of the DS-CDMA except that the user codes are IFFT transformed. Our formulation for the near-far resistance is applied to either blind or non-blind MMSE detectors. Computer simulations confirm theoretical findings.