POWER ALLOCATION FOR FULL-DUPLEX COOPERATIVE NON-ORTHOGONAL MULTIPLE ACCESS SYSTEM

Abstract

Future-generation wireless communication will encounter tremendous mo- bile data traffic. The main challenging requirements of future networks are increasing the connectivity and achieving higher spectral efficiency compared to previous generations. Non-orthogonal multiple access (NOMA) is an en- abling access scheme for future generation wireless technology. It can enhance system performance, increase spectral efficiency and connectivity. However, the weak user suffers poor performance due to the interference and poor channel quality. Full-duplex cooperative NOMA (FD C-NOMA) is an attrac- tive solution to help the weak user by allowing the strong user to relay the weak user’s signal simultaneously without much degrading the strong user performance. In this thesis, various wireless technologies such as NOMA, cooperative communication, FD, and simultaneous wireless information and power transfer (SWIPT) are investigated to enhance system performance. Dif- ferent new feasible successive interference cancellation (SIC) techniques are applied to help the weak user to decode its own information. In addition, a power control strategy on the relay power for FD C-NOMA schemes is pro- posed to reduce the self-interference effect while ensuring an effective link to the weak user. Moreover, the power allocation to improve the system perfor- mance is considered for different objective functions such as maximizing the minimum achievable rate (max-min) and the sum-rate. In all considered sce- narios, a closed-form solution is derived and compared with Fixed Power Al- location (FPA), Fractional Transmit Power Allocation (FTPA), and half-duplex (HD) C-NOMA. Numerical simulation results show that the max-min power allocation’s effectiveness in enhancing the weak user’s rate performance with considerably better user fairness. The proposed FD C-NOMA system using sum-rate optimization attains better sum-rate performance compared to other schemes and close to the conventional NOMA.