Joint Beamwidth and Power Optimization in MmWave Hybrid Beamforming-NOMA Systems
Joint Beamwidth and Power Optimization in MmWave Hybrid Beamforming-NOMA Systems
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DOI：
10.1109/twc.2020.3042518
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发表时间：
2021-04
影响因子：
10.4
通讯作者：
Mojtaba Ahmadi Almasi;Lisi Jiang;H. Jafarkhani;H. Mehrpouyan
中科院分区：
文献类型：
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作者：
Mojtaba Ahmadi Almasi;Lisi Jiang;H. Jafarkhani;H. Mehrpouyan
在毫米波（mmWave）频率中使用定向传输导致有限的信道相干时间。在本文中，我们考虑有限的信道相干时间的非正交多址（NOMA）毫米波混合波束形成系统。由于相干时间有限，混合波束形成器的波束宽度影响波束训练时间，进而直接影响数据传输速率。为了研究这种权衡，我们利用组合波束训练算法。然后，我们制定了一个和速率表达式，该表达式考虑了信道相干时间和波束训练时间以及用户的功率和其他系统参数。此外，通过在功率分配和波束宽度优化之间迭代来解决联合功率和波束宽度优化问题。在功率分配时，我们使用对数指数重构和序列参数凸逼近（SPCA）方法来解决非凸问题。由于波束宽度优化涉及太多的变量，我们提出了一种算法，迭代用户集群之间。仿真结果表明，优化后的毫米波混合波束成形-NOMA系统与采用模拟波束成形和传统多址技术的NOMA系统相比，可以获得更高的和速率。
The use of directional transmission in millimeter-Wave (mmWave) frequencies results in limited channel coherence time. In this paper, we take the limited channel coherence time into account for non-orthogonal multiple access (NOMA) in mmWave hybrid beamforming systems. Due to the limited coherence time, the beamwidth of the hybrid beamformer affects the beam-training time, which in turn directly impacts the data transmission rate. To investigate this trade-off, we utilize a combined beam-training algorithm. Then, we formulate a sum-rate expression which considers the channel coherence time and beam-training time as well as users’ power and other system parameters. Further, a joint power and beamwidth optimization problem is solved by iterating between the power allocation and the beamwidth optimization. When allocating the power, we use the log-exponential reformulation and the sequential parametric convex approximation (SPCA) methods to solve the non-convex problem. Since beamwidth optimization involves too many variables, we propose an algorithm which iterates between clusters of users. Numerical results show that the optimized mmWave hybrid beamforming-NOMA system can achieve much higher sum-rates compared to NOMA with analog beamforming and traditional multiple access techniques.