Cooperative transmission is a promising technology to expand communication range and improve system performance for underwater optical wireless communications (UOWCs). To adequately exploit the benefits of cooperative UOWCs, the relay selection and power allocation problems require to be explored. This paper investigates the relay selection and power allocation issues for the cooperative UOWC in the presence of solar radiation noise. Specifically, the cooperative UOWC based on amplify-and-forward (AF) relaying is modeled, where the effects of absorption, scattering, and solar radiation noise are all considered. We design two optimization schemes that minimize the energy consumption and maximize the overall signal-to-noise ratio (SNR), respectively. Both schemes are proved to be strictly quasi-convex and solved by Levenberg-Marquardt (LM) algorithm. The effectiveness of the proposed schemes is evaluated in line-of-sight (LOS) links and non-line-of-sight (NLOS) links, and the main factor affecting the relay selection and power allocation are derived for both LOS links and NLOS links.

中文翻译：

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水下协作光无线网络的联合中继选择和功率分配

协作传输是一种有前途的技术，可以扩大水下光无线通信（UOWC）的通信范围并提高系统性能。为了充分利用合作 UOWC 的好处，需要探索中继选择和功率分配问题。本文研究了在存在太阳辐射噪声的情况下协作 UOWC 的继电器选择和功率分配问题。具体而言，对基于放大转发 (AF) 中继的协作 UOWC 进行了建模，其中都考虑了吸收、散射和太阳辐射噪声的影响。我们设计了两种优化方案，分别使能耗最小化和总体信噪比（SNR）最大化。两种方案都被证明是严格拟凸的，并通过 Levenberg-Marquardt (LM) 算法求解。