Joint Beamwidth and Power Optimization in MmWave Hybrid Beamforming-NOMA Systems

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 t...

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Bibliographic Details
Published in:IEEE transactions on wireless communications 2021-04, Vol.20 (4), p.2442-2456
Main Authors: Almasi, Mojtaba Ahmadi, Jiang, Lisi, Jafarkhani, Hamid, Mehrpouyan, Hani
Format: Article
Language:English
Subjects:
Algorithms
Approximation
Array signal processing
Beamforming
beamwidth control
Clustering algorithms
Coherence
Coherence time
Data transmission
Hybrid power systems
Hybrid systems
Millimeter waves
mmWave communication
NOMA
Nonorthogonal multiple access
Optimization
Resource management
sum-rate
Transmission rate (communications)
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Summary: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.
ISSN:1536-1276
1558-2248
DOI:10.1109/TWC.2020.3042518