EFFECT OF USER CLUSTERING WITH DYNAMIC POWER ALLOCATION ON DOWNLINK NON-ORTHOGONAL MULTIPLE ACCESS

Abstract

Non-Orthogonal Multiple Access (NOMA) technique is an aspiring scheme proposed for 5G to accomplish better user-fairness. NOMA technique uses power domain for multiplexing of various users and transmits non-orthogonally on the same frequency spectrum. In this scheme, successive interference cancellation (SIC) is used to decode received message signal. This thesis describes the principle of downlink NOMA and a closed-form expression is obtained for spectral e ciency of NOMA with xed power allocation. Then user clustering is explained with xed power allocation. The numerical results are veri ed by using simulations to demonstrate that the xed-NOMA o ers larger sum-rate than the conventional orthogonal multiple access and also improves individual user throughput by using NOMA. Furthermore, power allocation is optimized, and throughput is obtained for the di erent cluster size. We can observe how power allocation a ects throughput performance and user fairness. In the last section, user clustering is performed with dynamic power allocation. This proposed scheme is used under the more practical scenario. In xed NOMA, the user having the best channel condition is paired with the user having the worst channel condition, however, in the case of the dynamic power allocation, the user having similar channel condition are paired to achieve better sum throughput. Numerical results compare the performance of NOMA with conventional scheme, i.e. OMA and throw light on the signi cance of NOMA in various channel conditions.