CSEE Seminar Series - Sparse or Dense: Codebook Selection for Overloaded Multiuser Communications

Sparse code multiple access (SCMA) is an enabling multiple access technique for massive connectivity in 5G communication.

By exploiting the sparsity of codebook structure using the efficient belief propagation algorithm, SCMA tends to achieve error rate performance approaching to that of the maximum-likelihood receiver.

That being said, the maximum diversity order of any SCMA system is less than the effective number of resource nodes given to each user. This fundamentally limits the performance enhancement of SCMA systems, regardless of any sparse codebook and/or any advanced receiver. To attain enhanced massive connectivity, it is interesting to ask: how can we select codebooks for overloaded multiuser communication system?

In this talk, Dr Liu will first review the state-of-the-art of SCMA, focusing on its codebook design rules, methodologies, and performance analysis. Then, he will introduce a class of dense codebooks (designed from certain advanced algebraic tools) which is capable of achieving full diversity order in fading channels. Simulations show that such dense codebooks lead to significantly improved error rate performance over SCMA systems.