On the Performance of NOMA and Coded Multicasting in Cache-Aided Wireless Networks

Coded multicasting has been widely studied as an effective content delivery solution for wireless caching at user equipment. Recently, non-orthogonal multiple access (NOMA) has been studied as an alternative delivery approach in cache-aided network. Both schemes allow multiple users to access the same frequency/time/code resource and thus offer enhanced spectral efficiency. By exploiting the information available in the cache, the users can successfully decode the requested message through cache-enabled interference cancellation (CIC) in NOMA or XOR decoding in coded multicasting. These techniques require user pairing/clustering in order to address the complexity issue arising from handling large number of users. Nevertheless, it is not known which delivery technique performs better under different user pairing scenarios. Based on two-user pairing, we study the performance of NOMA and coded multicasting in terms of probability of sum rate comparison and outage probability under the situation in which the users are randomly located in a circular cell. Both analytical and simulation results show that NOMA is better than coded multicasting when the channel gains of the paired users are highly distinctive while coded multicasting is preferable when the users' channel gains are similar.