LAUSR

In this paper, we consider an intelligent reflecting surface (IRS) aided maritime cooperative communication system, where multiple relay ships each equipped with an active decode-and-forward relay and a passive IRS assist the downlink transmission between the base station (BS) and the destination ship. Each relay ship operates in either the active mode with both active relaying and IRS reflection or the passive mode with only IRS reflection. We formulate and solve new problems to minimize the total transmit power of the BS and active relay ships, by jointly optimizing the relay mode selection vector, transmit power, as well as active and passive beamforming, subject to the quality of service of the destination ship. The joint optimization problem is solved by alternatively solving two sub-problems, i.e., the joint mode selection and power control sub-problem, and the joint active and passive beamforming sub-problem. Two algorithms based on exhaustive searching and many-to-one matching are respectively proposed for solving the first sub-problem, while a semidefinite programming-based algorithm is proposed for solving the second sub-problem. Numerical results demonstrate the good performance of the proposed joint mode selection and beamforming algorithm and the advantage of the proposed IRS-aided maritime cooperative communication system in power saving.