Abstract
This paper investigates a symbiotic unmanned aerial vehicle (UAV)-assisted intelligent reflecting surface (IRS) radio system, where the UAV is leveraged to help the IRS reflect its own signals to the base station, and meanwhile enhance the UAV transmission by passive beamforming at the IRS. First, we consider the weighted sum bit error rate (BER) minimization problem among all IRSs by jointly optimizing the UAV trajectory, IRS phase shift matrix, and IRS scheduling, subject to the minimum primary rate requirements. To tackle this complicated problem, a relaxation-based algorithm is proposed. We prove that the converged relaxation scheduling variables are binary, which means that no reconstruct strategy is needed, and thus the UAV rate constraints are automatically satisfied. Second, we consider the fairness BER optimization problem. We find that the relaxation-based method cannot solve this fairness BER problem since the minimum primary rate requirements may not be satisfied by the binary reconstruction operation. To address this issue, we first transform the binary constraints into a series of equivalent equality constraints. Then, a penalty-based algorithm is proposed to obtain a suboptimal solution. Numerical results are provided to evaluate the performance of the proposed designs under different setups, as compared with benchmarks.
Highlights
With the ever-growing sales of mobile devices and Internet of Things devices, current network architectures are becoming overwhelmed by growing data traffic demands [1]
Numerous technologies such as millimeter wave communications, ultra-dense networks, and massive multiple-input multiple-output (MIMO) [2]–[4] have been proposed to address this problem, they are usually realized with very large energy consumption and high hardware cost due to the large number of radio frequency (RF) chains required at the terminals
We prove that the obtained scheduling results are the same as the binary results from the alternating optimization (AO) method, which means that no reconstruct strategy is needed, and the primary rate requirements of unmanned aerial vehicle (UAV) are always satisfied
Summary
With the ever-growing sales of mobile devices and Internet of Things devices, current network architectures are becoming overwhelmed by growing data traffic demands [1]. Numerous technologies such as millimeter wave (mmWave) communications, ultra-dense networks, and massive multiple-input multiple-output (MIMO) [2]–[4] have been proposed to address this problem, they are usually realized with very large energy consumption and high hardware cost due to the large number of RF chains required at the terminals. IRS is a promising solution for improving the spectral and energy efficiency of wireless networks, and paving the way to the green networks of the future
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