Performance Analysis And Optimization Of Non-orthogonal Multiple Access Technologies In Wireless Communication Networks

Nowadays,with the rapid growth of mobile multimedia services,available radio spectrum becomes more and more scarce and this has become one of the most vital challenges in wireless and mobile network communications.In recent years,the research of Non-Orthogonal Multiple Access(NOMA)technology has proved it is a promising technology to considerably improve the spectrum efficiency.As a result,NOMA is widely considered as the most promising access technology for Fifth-Generation(5G)mobile networks to support services such as massive Machine Type Communications(m MTC).NOMA technology can serve multiple users at the same time,using the same frequency and code,therefore,in comparison with orthogonal multiple access(OMA)technologies,can significantly improve the spectrum efficiency.Based on the most recent research progress on NOMA technology,our work mainly focuses on the performance analysis and optimization of NOMA technology taking into consideration of some specific traffic and system models.The main contributions of our research work are as follows:(1)In our work,we propose a mixed multi-cast and uni-cast traffic application supported by a cooperative NOMA wireless system.The performances of full-duplex and half-duplex modes are studied,where the mixed service scenario consists of several multicast users and one unicast user.In such a system,a cooperative relay path selection strategy is employed to select the best channel conditioned multicast user to relay the unicast user's signal.The unicast user outage probability and the relay users capacity in closed-form are then derived.Mont-Carlo simulation results validate the analysis and show that the proposed scheme can significantly enhance unicast user outage probability while maintaining the same ergodic capacity for the relay users.(2)We then expand the NOMA wireless system model to be more realistic by taking into consideration of channel estimation errors and study the base station(BS)power allocation strategy to maximize the downlink achievable rate of each user.Assuming constant base station total transmission power condition,we finally derive a closed-form solution which can optimize power allocation to maximize the minimum user achievable rate.Simulation results show that proposed optimal power allocation method significantly outperforms fixed power allocation method.Equally importantly,it is observed that the minimum achievable rate of the users in the presence of channel estimation error is noticeably worse than that in perfect channel condition,which verifies the importance of considering channel estimation errors in similar analysis.