In this letter, we introduce a novel relaying scheme together with a joint energy beamforming (EB) and time allocation optimization to meet requirements about energy efficiency and hardware constraints of batteryless IoT networks. First, we propose an intelligent relaying scheme using RF-powered gateways as relay nodes to deliver information from batteryless IoT devices to a hybrid access point (HAP). The HAP can also transfer energy to the gateways and batteryless devices using EB techniques. The energy from HAP will be then used to supply power for gateways and as a communications means to transmit data for batteryless devices. We then formulate a sum-rate maximization problem by jointly optimizing the EB vectors, time scheduling, and power allocation. Since the optimization problem is non-convex, we exploit EB characteristics for data backscattering and employ variable substitutions and semidefinite relaxation techniques to transform it into a convex one. After that, a low-complexity method is proposed to obtain the optimal solution in a closed-form. Simulation results confirm that the proposed scheme can achieve significant sum-rate gain.

中文翻译：

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反向散射然后转发：无电池物联网网络的中继方案

在这封信中，我们介绍了一种新颖的中继方案以及联合能量波束成形 (EB) 和时间分配优化，以满足无电池物联网网络的能源效率和硬件限制要求。首先，我们提出了一种智能中继方案，使用射频供电的网关作为中继节点，将信息从无电池物联网设备传送到混合接入点 (HAP)。HAP 还可以使用 EB 技术将能量传输到网关和无电池设备。然后，来自 HAP 的能量将用于为网关供电，并作为通信手段为无电池设备传输数据。然后，我们通过联合优化 EB 向量、时间调度和功率分配来制定和速率最大化问题。由于优化问题是非凸的，我们利用 EB 特性进行数据反向散射，并采用变量替换和半定松弛技术将其转换为凸函数。之后，提出了一种低复杂度的方法来获得封闭形式的最优解。仿真结果证实，所提出的方案可以实现显着的总速率增益。