الفهرس 
PERFORMANCE STUDY OF POWER ALLOCATION SCHEMES IN ULTRA-DENSE NETWORKS
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Abstract
In this thesis, user association and power allocation are studied in ultra-dense wireless communication networks, in which access points are densely deployed. The thesis contribution is two-fold. First, with the objective of increasing the system{u2019}s uplink throughput, two different approaches are proposed for resource sharing. Interference resulting from such resource sharing is reduced by heuristically optimizing the user association to access points as well as power allocation to each user. The thesis compares various power allocations schemes, such as the well-known water-filling algorithm, the recently adopted non-orthogonal multiple access (NOMA), as well as others. It is shown that while NOMA guarantees throughput fairness among users, other power allocation schemes might achieve higher aggregate throughput at the expense that some users are deprived the privilege to transmit. Therefore, it is concluded that in date-centric applications, e.g. Internet-of-things (IoT) and machine-type-communications (MTC) applications, where higher data rate transmissions are prioritized irrespective the transmitting nodes, NOMA cannot be recommended as an optimum solution. In this thesis also, downlink NOMA transmission in ultra-dense networks is studied. Solutions for access points grouping, user association and resource sharing among users are proposed taking into consideration access point locations as well as channel state information. A three-cell case is examined, and the performance of NOMA is evaluated in three different settings; 1) NOMA within each cell with all three cell sharing same spectral resources, 2) NOMA within each cell, while each cell uses unshared spectral resources, and 3) the legacy orthogonal multiple access case. It is shown that employing NOMA without resource sharing among cell achieves better throughout performance, especially at high transmit powers