Potential impact of rate-splitting multiple access on cellular communications

The progress in the field of multiple access techniques keeps alive the hope that multiple access systems approaching the ultimate limit in terms of bandwidth efficiency are possible. The bandwidth efficiency of a spread spectrum multiple access (SSMA) system and that of an ideal multiple access technique are compared under various scenarios pertinent to cellular communications. The scenarios are: (1) single cell and power control for both schemes; (2) single cell and no power control for the ideal system; (3) multi-cell and no power control. It is shown that in all three cases there is a considerable gap between the bandwidth efficiency of SSMA and that of an ideal system. This leads one to expect that rate-splitting multiple access (RSMA)-a new technique whose decoder is based on interference cancellation (IC)-has the potential for a significant impact even if perfect IC is not possible. It is also found that IC is very valuable even in a multicell environment, provided that there is no power control.