Beamforming Design for IRS-and-UAV-Aided Two-Way Amplify-and-Forward Relay Networks in Maritime IoT

TL;DR

The paper tackles maximizing the minimum exchange rate in an IRS-and-UAV-aided two-way AF relay network for maritime IoT, where two ships exchange data via an IRS mounted on a UAV and an AF relay. It develops two alternating-optimization strategies: LC-ZF-SCA, which uses a zero-forcing closed-form for the AF beamforming and SCA for IRS phase shifts, and ONS-SDP-PSCA, which derives a high-performance AF beamformer via SVD/ONS and solves SDP subproblems with GFP-based convexifications and rank-one penalties for the IRS phase matrices. LC-ZF-SCA achieves lower complexity with substantial rate gains, while ONS-SDP-PSCA delivers superior rates at higher computational cost; simulations show up to 90.6% gains over baselines at $P=30$ dBm and that rate improvements widen with more IRS elements and relay antennas. The results demonstrate the practical viability of joint AF beamforming and IRS phase-shift design in hybrid IRS-UAV maritime networks, offering scalable options for different complexity-performance trade-offs.

Abstract

In this paper, an intelligent reflecting surface (IRS)-and-unmanned aerial vehicle (UAV)-assisted two-way amplify-and-forward (AF) relay network in maritime Internet of Things (IoT) is proposed, where ship1 ($\text{S}_1$) and ship2 ($\text{S}_2$) can be viewed as data collecting centers. To enhance the message exchange rate between $\text{S}_1$ and $\text{S}_2$, a problem of maximizing minimum rate is cast, where the variables, namely AF relay beamforming matrix and IRS phase shifts of two time slots, need to be optimized. To achieve a maximum rate, a low-complexity alternately iterative (AI) scheme based on zero forcing and successive convex approximation (LC-ZF-SCA) algorithm is presented. To obtain a significant rate enhancement, a high-performance AI method based on one step, semidefinite programming and penalty SCA (ONS-SDP-PSCA) is proposed. Simulation results show that by the proposed LC-ZF-SCA and ONS-SDP-PSCA methods, the rate of the IRS-and-UAV-assisted AF relay network surpass those of with random phase and only AF relay networks. Moreover, ONS-SDP-PSCA perform better than LC-ZF-SCA in aspect of rate.

Figures (7)

• Figure 1: An IRS-and-UAV-assisted two-way AF relay network in maritime IoT.
• Figure 2: Complexity versus the number $N$ of IRS units given $(M, D1, D2, \varepsilon)=($2, 6, 6, 0.1$)$.
• Figure 3: Complexity versus the number $M$ of AF relay antennas given $(N, D1, D2, \varepsilon)=($256, 6, 6, 0.1$)$.
• Figure 4: Convergence of the proposed two methods given $(M, N)=($2, 128$)$.
• Figure 5: Achievable rate versus total transmit power given $(M, N)=($2, 128$)$.