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Title:	Signal-to-leakage ratio beamforming approach in cooperative non-orthogonal multiple access system
Authors:	Mohammed Fadhil Mahmood (P69792)
Supervisor:	Rosdiadee Nordin, Assoc. Prof. Ir. Dr.
Keywords:	Universiti Kebangsaan Malaysia -- Dissertations
Issue Date:	11-Jun-2020
Description:	Non-Orthogonal Multiple Access (NOMA) is an emerging multiple access technique proposed for the Fifth-Generation (5G) wireless communications that allow multiple users to share the same time and frequency resource using different power level, thus yields a significant spectral efficiency improvement. To prevent the performance degradation of the far users, cooperative NOMA is favored by squeezing the user with better channel conditions into a channel that is occupied by a user with worse channel conditions. Among the techniques available to guarantee achievable power level, a beamforming technique is selected with Successive Interference Cancellation (SIC) at the user receiver to separate the weak signal from the strong signal. The system capacity of cooperative multiuser (MU) communication is inefficient due to non-optimal co-channel interference suppression schemes and the interference from other users will further degrade system performance particularly after user cooperation. Moreover, in cooperative NOMA system, the existing power allocation strategies among users not been optimized and fair under various channel conditions. The main research objective is to propose Signal-to-Leakage Ratio (SLR) beamforming approach in MU-Multiple-Input-Multiple-Output (MU-MIMO) in the downlink cooperative system to improves the signal power at the intended user and reduce interference to non-intended users and enhance SIC technique by separating the leakage signal from the desired signal after user cooperation. The methodology involved derivation of the maximal SLR (max-SLR) beamforming vector to achieve extra leakage power without increasing complexity. Then the additional leakage power is used to enhance SIC technique among cooperative users. Finally, a mathematical model based on the Nash Bargaining Solution (NBS) game is proposed to implement a fair scheme for optimal power allocation in beamforming cooperative NOMA system. All simulations are validated over Rayleigh fading channel in the first time slot and over Rician fading channel in the second time slot. Results have shown that the coded cooperative scheme outperformed non-cooperative scheme by 7 dB in term of Signal-to-Noise Ratio (SNR) at Bit Error Rate (BER) of about 10-5. Furthermore, the NBS power allocation scheme further improved the SNR by 1 dB compared to the non-cooperative scheme, and about 2.5 dB compared with the MIMO-NOMA. Besides that, fairness index is improved by about 0.1 (22% higher) compared to other latest existing literature. The significant SNR and fairness improvement achieved between users from the SLR beamforming approach has shown that cooperative NOMA offers huge potential as the next multiple access technique for the 5G system.,Ph.D.
Pages:	149
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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