Statistical modelling and reduction of multiple access interference power in wideband DS-CDMA and MC-CDMA communications systems

Abstract

Most standardisation bodies have based their 3G cellular systems on DS-CDMA (W-CDMA, UMTS, cdma2000). With 4G systems desiring improved services and quality of service standards, this thesis investigates mutlicarrier CDMA (MC-CDMA) as a genuine air interface candidate. A statistical model of the total MAI power incurred over the uplink channel is shown to be very accurately characterised by the Nakagami-m distribution for both asynchronous DS-CDMA and MC-CDMA techniques. Two new CDMA schemes, DF/DS-CDMA and DF/MC-CDMA, are proposed, based on the dual-frequency (DF) switching technique introduced in this thesis. These proposed DF schemes offer substantial MAI reduction upon asynchronous reception and clearly outperform (MAI and BER) the standard DS-CDMA and MC-CDMA systems, however, additional bandwidth is required.