In this article, we investigate a two-hop decode-and-forward (DF) multicasting multiple-input multiple-output (MIMO) wireless relay communication system. Different to conventional systems, the radio frequency (RF) energy from the source node is harvested at the relay node and used for forwarding signals to a group of receivers. Considering the structure of the energy harvesting (EH) relay node, we present a power splitting (PS) based protocol and a novel time switching (TS) based protocol by introducing two additional TS factors. For both protocols, we maximize the system mutual information (MI) of the multicasting MIMO relay system by jointly optimizing the source and relay covariance matrices under the constraints of the source energy and the relay harvested energy. In addition, a practical nonlinear EH model is adopted, where the energy harvested by the relay node is bounded as the incident RF signal power increases, and the harvested power is zero when the input power is below the minimum power for harvesting. For the TS based protocol, we also consider peak transmission power constraints at both the source and relay nodes. The performance of the proposed algorithms is verified via numerical simulations. The results demonstrate that the novel TS based protocol achieves a larger MI than the conventional TS protocol. The PS and TS based protocols achieve tradeoffs at different source power levels. In particular, compared with the PS based protocol, the proposed novel TS based protocol can reach a higher system MI when the EH bound is not reached, while the former protocol reaches a higher MI when the EH circuit is saturated. We show that the peak harvested energy constraint plays an important role in selecting the optimal location of the relay node.

中文翻译：

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具有无线信息和功率传输的 DF 多播 MIMO 中继系统的联合收发器优化

在本文中，我们研究了两跳解码转发 (DF) 多播多输入多输出 (MIMO) 无线中继通信系统。与传统系统不同，来自源节点的射频 (RF) 能量在中继节点处收集并用于将信号转发到一组接收器。考虑到能量收集 (EH) 中继节点的结构，我们通过引入两个额外的 TS 因素，提出了一种基于功率分配 (PS) 的协议和一种新型的基于时间切换 (TS) 的协议。对于这两种协议，我们通过在源能量和中继收集能量的约束下联合优化源和中继协方差矩阵来最大化组播 MIMO 中继系统的系统互信息 (MI)。此外，采用了实用的非线性 EH 模型，其中中继节点采集的能量随着入射射频信号功率的增加而有界，当输入功率低于采集的最小功率时，采集的功率为零。对于基于 TS 的协议，我们还考虑了源节点和中继节点的峰值传输功率限制。通过数值模拟验证了所提出算法的性能。结果表明，新的基于 TS 的协议实现了比传统 TS 协议更大的 MI。基于 PS 和 TS 的协议在不同的源功率水平上实现了权衡。特别是，与基于 PS 的协议相比，所提出的新的基于 TS 的协议可以在未达到 EH 边界时达到更高的系统 MI，而前一种协议在 EH 电路饱和时达到更高的 MI。