Partial transmit sequence based low complexity receiver for multi-user STBC MC-CDMA system

Abstract

Space Time Block Code Multi Carrier Code Division Multiple Access (STBC MC-CDMA) is a promising technology for 4G wireless communication systems. STBC is a special form of Multiple Input Multiple Output (MIMO) originally employed for 2 transmit antennas (Nt) and 1 receive antenna (Nr) by Alamouti under flat fading conditions. So application of STBC to frequency selective channel is challenging and has attracted attention of many researchers. Hence, STBC is integrated with multicarrier techniques such as Orthogonal Frequency Division Multiplexing (OFDM) and Multi Carrier Code Division Multiple Access (MC-CDMA), which convert frequency selective channel to several flat fading channels thereby eliminating ISI and in turn need of equalization. Like all other multicarrier techniques STBC MC-CDMA also suffers from high Peak-to-Average Power (PAPR) problem. To combat the problem ofhigh PAPR, many techniques have been proposed,among which Partial Transmit Sequence (PTS) is considered to be the best PAPR reduction schemebut at a cost of high computational complexity. This dissertation mainly focusses on implementation of PTS technique to STBC MC-CDMA scheme for downlink scenario. Also, a low complexity receiver is designed for the above scheme where the equalization is carried out in time domain basis. Also the proposedSTBC MC-CDMA with PTS scheme is comparedwith Single Input Single Output (SISO) MC-CDMA with PTS scheme in terms ofComplementary Cumulative Distribution Function (CCDF) andBit Error Rate(BER) performance. The simulation results verify that STBC MC-CDMA outperforms SISO MC-CDMA under fading conditions. Alsoas the no of users increase, CCDF performanceimproves and BER performance degrades.