Improving user performance in cooperative NOMA millimeter wave networks under two-phase operation protocol

Improving user performance is the most important target of 5G and beyond 5G millimeter wave cellular network systems. Thus, cooperative communication with assistance from additional hardware has been introduced as the potential solution. The paper proposes a two-phase cooperative communication system without utilizing the additional hardware to assist the users with bad channel conditions. Particularly, each Cell-Edge User (CEU) is served by both the nearest and second nearest BSs where the former is the source and the latter works as the relay. In addition, the Non-Orthogonal Multiple Access (NOMA) technique is used to allocate the radio resource and power for the relays. To capture the performance behavior of the proposed system, the millimeter wave properties, which are modeled by Nakagami-m and the Stretch Path Loss, are used to derive the performance metrics of Cell-Center User (CCU), CEU, and the typical user. Through analytical results which are validated by Monte Carlo simulation, it is proved that the proposed system can provide a coverage probability of 0.93 (m=2) which is 13.4% higher than the system without cooperative communication. Moreover, the proposed system can achieve an 8% higher data rate but consume an 16.7% power less than the system with full cooperative communication.