Throughput Maximization in Wireless Powered Communication Networks
Throughput Maximization in Wireless Powered Communication Networks
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DOI：
10.1109/twc.2013.112513.130760
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发表时间：
2014-01-01
影响因子：
10.4
通讯作者：
Zhang, Rui
中科院分区：
文献类型：
--
作者：
Ju, Hyungsik;Zhang, Rui
本文研究了新兴的无线供电通信网络，其中一个混合接入点（H-AP）与恒定电源协调无线能量/信息传输到/从一组分布式用户，没有其他能源。提出了一种“收集然后发送”协议，其中所有用户首先在下行链路（DL）中收集由H-AP广播的无线能量，然后通过时分多址（TDMA）在上行链路（UL）中向H-AP发送它们的独立信息。首先，我们研究了所有用户的总吞吐量最大化，通过联合优化DL无线功率传输与用户的UL信息传输的时间分配，给出了基于用户的DL和UL信道以及它们的平均收获能量值的总时间约束。通过应用凸优化技术，我们得到了封闭形式的最佳时间分配，以最大化总吞吐量的表达式。我们的解决方案揭示了一个有趣的“双近远”现象，由于DL和UL距离相关的信号衰减，其中一个远离H-AP的用户，其接收到更少的无线能量比一个较近的用户在DL中，必须发送更多的功率在UL中的可靠的信息传输。其结果是，最大的总和吞吐量被证明是通过分配更多的时间比远用户近的用户，从而导致在不同的用户之间的不公平的速率分配。为了克服这个问题，我们还提出了一个新的性能指标，所谓的共同吞吐量与额外的约束，所有的用户都应该被分配以平等的速率，而不管他们的距离的H-AP。我们提出了一个有效的算法来解决公共吞吐量最大化问题。仿真结果表明，共同吞吐量的方法来解决无线供电通信网络中的新的双远近问题的有效性。
This paper studies the newly emerging wireless powered communication network in which one hybrid access point (H-AP) with constant power supply coordinates the wireless energy/information transmissions to/from a set of distributed users that do not have other energy sources. A "harvest-then-transmit" protocol is proposed where all users first harvest the wireless energy broadcast by the H-AP in the downlink (DL) and then send their independent information to the H-AP in the uplink (UL) by time-division-multiple-access (TDMA). First, we study the sum-throughput maximization of all users by jointly optimizing the time allocation for the DL wireless power transfer versus the users' UL information transmissions given a total time constraint based on the users' DL and UL channels as well as their average harvested energy values. By applying convex optimization techniques, we obtain the closed-form expressions for the optimal time allocations to maximize the sum-throughput. Our solution reveals an interesting "doubly near-far" phenomenon due to both the DL and UL distance-dependent signal attenuation, where a far user from the H-AP, which receives less wireless energy than a nearer user in the DL, has to transmit with more power in the UL for reliable information transmission. As a result, the maximum sum-throughput is shown to be achieved by allocating substantially more time to the near users than the far users, thus resulting in unfair rate allocation among different users. To overcome this problem, we furthermore propose a new performance metric so-called common-throughput with the additional constraint that all users should be allocated with an equal rate regardless of their distances to the H-AP. We present an efficient algorithm to solve the common-throughput maximization problem. Simulation results demonstrate the effectiveness of the common-throughput approach for solving the new doubly near-far problem in wireless powered communication networks.