Performance analysis of swipt enabled non-orthogonal multiple access assisted multiple relay cooperative networks / Mahrukh Liaqat

Mahrukh , Liaqat (2021) Performance analysis of swipt enabled non-orthogonal multiple access assisted multiple relay cooperative networks / Mahrukh Liaqat. PhD thesis, Universiti Malaya.

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Abstract

Non-orthogonal multiple access (NOMA) scheme is emerging as a favorable multiple access scheme for future 5G networks. Compared to orthogonal multiple access (OMA) techniques, NOMA provides spectral efficiency, user fairness, better connectivity, enhanced data rate and reduced latency. On the other hand, in wireless networks, cooperation is a well-recognized technique for performance enhancement. Cooperative networks offer multiple desirable advantages, including high performance, reliability and greater coverage area. NOMA has features that can provide opportunities of improved performance and better spectral utilization for downlink cooperative networks. Modern communication systems operate under energy constraints. Simultaneous wireless information and power transmission (SWIPT) is a way of energy harvesting (EH), which allows to exploit the same RF signal for both EH and information processing. Integration of Cooperation, NOMA and SWIPT can provide energy efficient, reliable and spectral efficient networks. Therefore, this study aims to design energy harvesting enabled cooperative NOMA (C-NOMA) networks. In the first part, multiple relay downlink cooperative NOMA network with SWIPT is investigated where both useful signal and interfering signals are used to harvest energy. The closed form analytical expressions of outage probability are derived. Subsequently, impact of various parameter, including, number of available relay nodes, interfering signals, energy harvesting parameter, and energy conversion efficiency is shown on performance of proposed networks. The finding showed that system performance improves with the number of intermediate relaying nodes, transmit power, power of external interfering source and energy harvesting efficiency. It was identified that optimal location of relaying nodes is nearest to source. For device to device communication, it is important to consider spatial distribution of dynamically distributed users. Second part of the research focused to investigate the SWIPT enabled C-NOMA networks in the presence of interference with cooperation among spatially distributed NOMA users. The mathematical model to evaluate the outage probability and system throughput are provided and analyzed. The results demonstrated the positive impact of transmit SNR, number of available cooperating device, interference power and conversion efficiency, while performance was deteriorated with increase in radius of cooperative area and higher data rates. Due to energy harvesting, multiple channel gains get involved and best relay cannot be selected straightforwardly. In the third part of the work, a new relay selection scheme for C-NOMA networks with SWIPT is proposed. The selection scheme was designed by carefully considering all involved channels and circuit power consumption at relay node. Additionally, the selection scheme was extended of dynamic power allocation factors of NOMA users. For the proposed two-stage relay selection analytical expression of outage probability for delay-limited transmission are provided. A comparative analysis of partial relay selection and two-stage relay selection was conducted to find which schemes performs better under certain conditions. It was revealed that proposed scheme provides significant performance improvement, particularly at higher transmit SNR and number of relays. For all relay selection schemes, the optimal relay location was found closer to source node.

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