In this paper, a novel bidirectional backscatter-aided transmission protocol is proposed for wireless powered distributed wearable measurement networks, where we consider channel detection, backscatter-aided wireless power transfer (WPT) and backscatter-aided information transfer. First, the channel detection phase is allocated for both the AP and sensors to get the knowledge of channel state information (CSI) at the beginning of each time block. In the backscatter-aided WPT phase, all sensors harvest radio frequency (RF) energy by converting RF signals from the AP with time-division-multiple-access (TDMA). Finally, the backscatter-aided information transfer phase is allocated to sensors for transmitting their independent information to the AP by TDMA and the harvested energy at each sensor is consumed in this phase. The signals from/to a sensor to/from the AP will be reflected by all other sensors and the optimal reflection coefficient at helping sensors can be calculated according to CSI. Considering fairness among sensors, we maximize sum throughput with energy harvesting constraints and max–min throughput by jointly optimizing the time allocation and the reflection coefficients. Sum and max–min throughput maximization problems are formulated as two convex optimization problems. A low-complexity algorithm is designed to obtain optimal solutions of sum throughput maximization problem with the fairness constraint, and the optimal solutions for max–min throughput maximization are derived as closed-form expressions. Numerical results illustrate the effectiveness of the proposed protocol.

在本文中，提出了一种用于无线供电分布式可穿戴测量网络的新型双向反向散射辅助传输协议，其中我们考虑了信道检测、反向散射辅助无线电力传输 (WPT) 和反向散射辅助信息传输。首先，为 AP 和传感器分配信道检测阶段，以在每个时间块开始时获取信道状态信息 (CSI) 的知识。在反向散射辅助 WPT 阶段，所有传感器都通过使用时分多址 (TDMA) 转换来自 AP 的 RF 信号来收集射频 (RF) 能量。最后，反向散射辅助信息传输阶段分配给传感器，用于通过 TDMA 将其独立信息传输到 AP，并且在此阶段消耗每个传感器收集的能量。来自/来自传感器的信号到/来自AP的信号将被所有其他传感器反射，并且帮助传感器的最佳反射系数可以根据CSI计算。考虑到传感器之间的公平性，我们通过联合优化时间分配和反射系数来最大化具有能量收集约束和最大-最小吞吐量的总吞吐量。Sum 和 max-min 吞吐量最大化问题被公式化为两个凸优化问题。设计了一种低复杂度算法来获得具有公平性约束的总吞吐量最大化问题的最优解，并将最大-最小吞吐量最大化的最优解导出为封闭形式的表达式。数值结果说明了所提出的协议的有效性。