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

Abstract

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 beamtraining 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.

Reinforcement Learning-Based Joint Beamwidth and Beam Alignment Interval Optimization in V2I Communications

“…Other researchers have focused on optimizing the beamwidth by taking into consideration the beam alignment overhead in order to maximize the throughput [17,[25][26][27][28][29][30][31][32]. The authors of [17] addressed the beam alignment-throughput tradeoff and developed an optimization problem that jointly considered the problems of beamwidth selection and scheduling in a mmWave network with multiple transmitter-receiver pairs.…”

“…The authors of [26] formulated a distributed antenna beamwidth optimization problem in device-to-device (D2D) communication and used multi-agent deep RL in order to find the antenna beamwidth of each D2D pair. The author of [27] proposed a joint power and beamwidth optimization algorithm for a NOMA system with limited coherence time. They found the power and beamwidth that maximize the sum rate by iterating between the power allocation and the beamwidth optimization.…”

Hybrid Terahertz Beamforming Relying on Channel Sparsity and Angular Orthogonality

“…Numerous hybrid beamforming designs have been conceived, especially for the millimeter-wave (mmWave) bands [14]- [17]. As for the connection between RF chains and antennas, both full-connection [18]- [20] and partial-connection architectures have been considered [21], [22].…”