Near-far resistance of multicarrier CDMA systems
Xiaodong Yue, H. Howard Fan · 2003
Multicarrier (MC) CDMA systems have been developed and rapidly gained popularity as they capitalize on both the resilience of MCM (multicarrier modulation) to MUI and the robustness of direct-sequence (DS) CDMA against frequency selectivity to mitigate both MUI and the intersymbol 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. We derive the theoretical near-far resistance of the MMSE detector in the MC-CDMA uplink (with and without cyclic prefix, CP). It turns out that the near-far resistance of MC-CDMA without CP has the same form as that of DS-CDMA, except that the user codes are IFFT transformed. Our formulation for near-far resistance is applied to either blind or non-blind MMSE detectors. Computer simulations confirm our theoretical findings.