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Optimal Resource Allocation and Transceiver Design for NOMA Relay NetworksAuthor: Zakir Hussain Shaik Date: 2019-07-18 Report no: IIIT/TH/2019/80 Advisor:Ubaidulla P AbstractMultiple access schemes play a crucial role in determining the performance of wireless networks. Already established access schemes which were part of the first generation (1G) to fourth generation (4G) cellular networks are time division multiple access (TDMA), frequency division multiple access (FDMA), code division multiple access (CDMA), and orthogonal frequency division multiple access (OFDMA). Though these techniques provide good service with simple receivers, they lack the ability to tackle emerging challenges arising due to monumental rise in the number of devices accessing wireless channel. In this background, non-orthogonal multiple access (NOMA) is seen as a suitable candidate not only to handle the connectivity challenges but also to improve spectral efficiency significantly. NOMA has been in the research literature for long, but it has garnered a lot of interest recently and extensive research is underway. Major hurdles in making NOMA a reality is the complexity involved in realizing successive interference cancellation (SIC) and imperfections in the channel state information (CSI). Hence to make NOMA a reality, effective algorithms that addresses these issues are needed. In this thesis, we focus on system design with optimal resource allocation and relay precoder design in a cooperative relay network, which employs NOMA. The proposed optimal design aims at maximizing the weighted sum-rate. The design problems turn out to be a non-convex optimization problem. We employ minorization-maximization (MM) technique to tackle the non-convexity of the optimization problems. Then, we address the problem of maximization of weighted sum-rate (WSR) while making the system performance robust to errors in the CSI. To solve this problem, we establish a relationship between WSR and weighted mean square error (WMSE) and solve the latter problem which is simpler to obtain a solution for the former. Cognitive radio (CR) is another technology that can help in solving the spectrum scarcity problem. NOMA and CR in combination is expected to improve spectral efficiency significantly. But very few works have explored the two technologies together. So, we consider the design of secondary system working on principles of NOMA in a cognitive radio network by ensuring interference to a primary node is below the permissible threshold. Then, we modify the algorithm to take into account the errors in the CSI and thus ensuring the system performance is robust. Apart from the theoretical analyses, extensive numerical simulations have been performed in order to verify the effectiveness of our proposed designs in terms of sum-rate, weighted mean square error, convergence, etc. Full thesis: pdf Centre for Communications |
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