Exploiting Intelligent Reflecting Surfaces in NOMA Networks: Joint Beamforming Optimization

By Xidong Mu, Yuanwei Liu, Li Guo, Jiaru Lin, Naofal Al-Dhahir. IEEE Transactions on Wireless Communications, 2019

376 citations recorded by the source corpus.

This paper investigates a downlink multiple-input single-output intelligent reflecting surface (IRS) aided non-orthogonal multiple access (NOMA) system, where a base station (BS) serves multiple users with the aid of IRSs. Our goal is to maximize the sum rate of all users by jointly optimizing the active beamforming at the BS and the passive beamforming at the IRS, subject to successive interference cancellation decoding rate conditions and IRS reflecting elements constraints. In term of the characteristics of reflection amplitudes and phase shifts, we consider ideal and non-ideal IRS assumptions. To tackle the formulated non-convex problems, we propose efficient algorithms by invoking alternating optimization, which design the active beamforming and passive beamforming alternately. For the ideal IRS scenario, the two subproblems are solved by invoking the successive convex approximation technique. For the non-ideal IRS scenario, constant modulus IRS elements are further divided into continuous phase shifts and discrete phase shifts. To tackle the passive beamforming problem with continuous phase shifts, a novel algorithm is developed by utilizing the sequential rank-one constraint relaxation approach, which is guaranteed to find a locally optimal rank-one solution. Then, a quantization-based scheme is proposed for discrete phase shifts. Finally, numerical results illustrate that: i) the system sum rate can be significantly improved by deploying the IRS with the proposed algorithms; ii) 3-bit phase shifters are capable of achieving almost the same performance as the ideal IRS; iii) the proposed IRS-aided NOMA systems achieve higher system sum rate than the IRS-aided orthogonal multiple access system.

Subfields: Aerospace Engineering, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/27ac0fb6685d8d79b956d0dbe884c1255c21007a

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Citations in the corpus

Enabling Large Intelligent Surfaces With Compressive Sensing and Deep Learning (2019, background): “The Critical Challenge: All the prior work in [5], [6], [9]–[11], [16] assumed that the knowledge about the channels between the LIS and the transmitters/receivers is available at the base station, either perfectly or with some error.”
Reconfigurable Intelligent Surfaces: Principles and Opportunities (2020, methodology): “[93] focused their attention on the sum rate maximization problem in an RIS-enhanced MISO NOMA system with both ideal and non-ideal assumptions.”
Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces: How It Works, State of Research, and The Road Ahead (2020, neutral): “In [213], the authors analyze the sum-rate optimization of an RIS-aided NOMA-based downlink MISO channel.”
Simultaneously Transmitting And Reflecting (STAR) RIS Aided Wireless Communications (2021, methodology): “The joint beamforming optimization problem was further studied by the authors of [14] for a RIS-assisted downlink multiple-input single-output (MISO) NOMA system, where the system sum rate was maximized for continuous and discrete RIS phase shifters, respectively.”
Evolution of NOMA Toward Next Generation Multiple Access (NGMA) for 6G (2021, methodology): “SCA Generally suboptimal solution Low complexity Continuous [51], [134], [155], [159], [167] [80], [112], [115], [168]–[170], [175]”
Channel Estimation and Passive Beamforming for Intelligent Reflecting Surface: Discrete Phase Shift and Progressive Refinement (2019, background): “, [6], [7], [15]–[27]) have mostly assumed perfect CSI available for all the individual channels between the IRS and its aided access point (AP) as well as users, which,”
Double-IRS Assisted Multi-User MIMO: Cooperative Passive Beamforming Design (2020, background): “, orthogonal frequency division multiplexing (OFDM) [6]– [10], multi-antenna communication [11]–[13], non-orthogonal multiple access (NOMA) [14]–[16], etc.”