Subcarrier and Power Allocation for Sparse Code Multiple Access

Resource allocation for Sparse Code Multiple Access (SCMA) systems is restricted by the codebook design for data transmission from different users simultaneously. The effect of the interference between users assigned to the same resource can result in severe degradation of performance. To alleviate this
problem, a practical subcarrier allocation approach is proposed in this paper. The proposed scheme has a lower complexity than existing methods while achieving close to optimal performance. It is based on a modified greedy algorithm and exploits the properties of multiuser systems by assigning opposite codebook patterns to adjacent users. A comparison between different allocation graph designs is explored and we introduce a low complexity
power allocation method with minimum rate constraints per user. The scheme is based on the water-filling principle adapted for multiuser sparse systems in the presence of interference. Simulation results show that the proposed scheme has close to optimal performance with lower computational complexity.