Codebook Design for PD-SCMA NOMA Systems

The hybrid power domain sparse code non-orthogonal multiple access (PD-SCMA) scheme multiplexes multiple users on a single resource element (RE) both in power and code domains, thus achieving a superior spectral efficiency. The multiplexing performance of such a scheme can be enhanced not only through deployment of sophisticated resource allocation schemes and low complexity robust multi-user detectors but also prudent multi-user multi-dimensional codebook design. By considering the key codebook design performance indicators (KPIs) in different channel use scenarios, this work assesses various known multi-dimensional constellation (MDC) design criterion on the performance of low-rate turbo-coded PD-SCMA NOMA system. In order to strike a balance with regard to good multi-dimensional modulation (MDM) and low complex detection, a low complex codebook design based on linear error correcting block codes is proposed. Unique user-specific rotation design based on quaternion rotation matrices is proposed with the aim of maintaining users symbol uniqueness for overloaded systems. Simulation results confirm that MDCs that satisfy design KPIs outperform others. Besides, the proposed user-specific rotation design remarkably enhances the BER performance of the block code based codebook design.