| Summary: | 碩士 === 國立中央大學 === 通訊工程學系 === 107 === In this thesis, we investigate a hierarchical Non-orthogonal multiple access cellular system
simultaneously shares the macrocell uplink spectrum with the microcell secondary user who is
unlicensed. We also attempt the NOMA which is expected to improve the system capacity of
wireless communication systems.
We jointly design the allocated power and the beamforming weights for each downlink
microcell user to maximize the capacity of the hierarchical NOMA cellular system. We consider
two methods: (1) Using minimax decision theory to find the user rate. (2) Using the sum-MSE
decision theory to find the sum rate. When we seek out user rate through Zero-forcing precoding
to eliminate the interference from the other beam users and find the optimal power allocation.
This problem is non-convex so we convert the aforementioned ZF user rate maximization
problem into a convex semi-definite relaxation (SDR) techniques. Because this problem is a
joint design non convex problem, it is difficult to jointly find the optimal solutions of power
allocation and beamforming design. We divide the problem into two steps to alternatively find
the optimal solutions.
Second method is using sum-MSE to seek the maximization sum rate of the system, while
satisfying the constraints of the interference power to the primary user, the required SINR for
secondary users, and the SIC requirement for the user in the same beam. This problem is also the non-convex problem so we solved it by SDR approach. And then we proof that sum-MSE
method sum rate is equal to the initial designing sum rate problem.
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