In this letter, beam selection and power allocation are investigated for maritime offshore communications. Considering the slow-changing network topology and the line-of-sight (LOS) dominant propagation of land-sea links, we define a beam configuration period (BCP) as a time span to contain numerous coherence intervals (CIs), and provide a two-timescale design by enforcing the long-term beam selection strategy and the short-term power allocation scheme only once in every BCP and in every CI, respectively. Since the beamforming configurations are updated much less frequently, the training overhead could be considerably reduced. Numerical results indicate that the proposed two-timescale design avoids heavy training overhead, and thus effectively enhances the performance of offshore communications.

中文翻译：

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海上海上通信的两时间尺度波束选择和功率分配

在这封信中，研究了海上海上通信的波束选择和功率分配。考虑到缓慢变化的网络拓扑和陆海链路的视距 (LOS) 主导传播，我们将波束配置周期 (BCP) 定义为包含众多相干间隔 (CI) 的时间跨度，并提供了一个通过在每个 BCP 和每个 CI 中分别仅执行一次长期波束选择策略和短期功率分配方案来实现双时间尺度设计。由于波束成形配置的更新频率要低得多，因此可以大大减少训练开销。数值结果表明，所提出的双时间尺度设计避免了繁重的训练开销，从而有效地提高了海上通信的性能。