Beamforming Techniques for Nonorthogonal Multiple Access in 5G Cellular Networks
Beamforming Techniques for Nonorthogonal Multiple Access in 5G Cellular Networks
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DOI：
10.1109/tvt.2018.2856375
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发表时间：
2018-07
影响因子：
6.8
通讯作者：
Faezeh Alavi;K. Cumanan;Z. Ding;A. Burr
中科院分区：
文献类型：
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作者：
Faezeh Alavi;K. Cumanan;Z. Ding;A. Burr
在本文中，我们开发了各种波束成形技术的下行链路传输多输入单输出非正交多址（NOMA）系统。首先，研究了一种具有理想信道状态信息的波束形成方法，为所有用户提供所需的服务质量。泰勒级数逼近和半定松弛（SDR）技术，重新制定原来的非凸功率最小化问题，一个易于处理的。此外，提出了一种基于公平性的波束形成方法，通过最大最小公式，以保持用户之间的公平性。接下来，我们考虑一个强大的计划，将信道的不确定性，其中的发射功率最小化，同时满足中断概率的要求，在每个用户。利用SDR方法，将原非凸问题转化为线性矩阵不等式形式，得到最优解。数值结果表明，鲁棒方案可以实现更好的性能相比，非鲁棒方案的速率满意率。此外，仿真结果证实，NOMA消耗略超过一半的正交多址所需的发送功率相同的数据速率要求。因此，NOMA有可能在未来5G网络及以后的传输功耗方面显着提高系统性能。
In this paper, we develop various beamforming techniques for downlink transmission for multiple-input single-output nonorthogonal multiple access (NOMA) systems. First, a beamforming approach with perfect channel state information is investigated to provide the required quality of service for all users. Taylor series approximation and semidefinite relaxation (SDR) techniques are employed to reformulate the original nonconvex power minimization problem to a tractable one. Furthermore, a fairness-based beamforming approach is proposed through a max–min formulation to maintain fairness between users. Next, we consider a robust scheme by incorporating channel uncertainties, where the transmit power is minimized while satisfying the outage probability requirement at each user. Through exploiting the SDR approach, the original nonconvex problem is reformulated in a linear matrix inequality form to obtain the optimal solution. Numerical results demonstrate that the robust scheme can achieve better performance compared to the nonrobust scheme in terms of the rate satisfaction ratio. Furthermore, simulation results confirm that NOMA consumes a little over half transmit power needed by orthogonal multiple access for the same data rate requirements. Hence, NOMA has the potential to significantly improve the system performance in terms of transmit power consumption in future 5G networks and beyond.