Differential Space–Time Shift Keying-Aided Successive-Relaying-Assisted Decode-and-Forward Cooperative Multiuser CDMA

A differential space-time shift keying (DSTSK)-aided successive-relaying-assisted multiuser decode-and-forward (DF) cooperative system is proposed. We employ low-complexity noncoherent detection, which requires channel state information (CSI) at neither the relay nodes (RNs) nor at the destination node (DN). More explicitly, the source nodes (SNs) employ differentially encoded phase-shift keying (PSK) modulation, whereas the RNs perform soft-input-soft-output multiple-symbol differential sphere decoding (SISO-MSDSD)-based DF relaying during the relaying phase. Similarly, DSTSK transmission is employed at the RNs, which is detected with the aid of SISO-MSDSD at the DN. More explicitly, three-stage serial-concatenated turbo encoding/decoding is employed throughout the system to enhance the attainable performance. Additionally, a maximum-minimum determinant-based configuration selection (MMBCS) algorithm is proposed to select the optimal DSTSK configuration for supporting a specific number of users. Moreover, we adopt a successive-relaying architecture for recovering the conventional 50% half-duplex relaying-induced throughput loss at the cost of supporting less users.