Proportional Fair Scheduling for Non-Orthogonal Multiple Access in Multiple Antenna Systems
Date Issued
2015
Date
2015
Author(s)
Hu, Ching-Wen
Abstract
In this thesis, we investigate non-orthogonal multiple access (NOMA) combined with multiple-input multiple-output (MIMO) system with zero-forcing (ZF) beamforming with the assumption of perfect CSIT. The key concept of the NOMA-MIMO is to superpose multiple user signals within a beam at the transmitter and apply successive interference cancellation (SIC) at the user terminal. Rather than using the ideal mathematical capacity model, we construct the physical-layer adaptive modulation and coding scheme (AMC) to accurately reflect the error propagation effect during the iterative decoding process. Therefore, the critical design issues on NOMA-MIMO include the precoding setting, the transmission power control among/within beams, the MCS selection and the scheduling strategy. In terms of fairness and sum rate, the proportional fair (PF) scheduling model is adopted to evaluate system performance. We first propose the metaheuristic scheduling approach based on the cross entropy method to solve the optimization problem of maximizing product of user sum rates. Then, we relax the maximization problem to the iterative scheduling scheme which is applied to the realistic systems such as LTE/LTE-A. To further reduce the computational complexity but not lose performance much, we consider to divide users into groups based on various criteria. In addition, the implementation of the NOMA-MIMO scenario in nowadays communication network is also taken into account. Simulation results show the proposed NOMA-MIMO system significantly outperforms conventional OMA-MIMO in not only system sum rate but also fairness by around $20\%$ to $30\%$. The more complicated cross entropy method improves $40\%$ gains compared with the iterative scheme. If we appropriately group users such as intra-beam correlation threshold, the perforance is almost the same while the complexity reduces by half. In addition, as users'' average SINRs are high, NOMA-MIMO even achieve more than $50\%$ gain. Therefore, NOMA-MIMO is expected to be a promising technique in the next generation of the cellular mobile communication which provides superior spectral efficiency by exploiting not only spatial-domain but also power-domain resources.
Subjects
MIMO
NOMA
PF
Type
thesis
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