User cooperation in wireless powered communication networks

Abstract

This paper studies user cooperation in the emerging wireless powered communication network (WPCN) for throughput optimization. For the purpose of exposition, we consider a two-user WPCN, in which one hybrid access point (H-AP) broadcasts wireless energy to two distributed users in the downlink (DL) and the users transmit their independent information using their individually harvested energy to the H-AP in the uplink (UL) through timedivision-multiple-access (TDMA). We propose user cooperation in the WPCN where the user which is nearer to the H-AP and has a better channel for DL energy harvesting as well as UL information transmission uses part of its allocated UL time and DL harvested energy to help to relay the far user's information to the H-AP, in order to achieve more balanced throughput. We maximize the weighted sum-rate (WSR) of the two users by jointly optimizing the time and power allocations in the network for both wireless energy transfer in the DL and wireless information transmission and relaying in the UL. Simulation results show that the proposed user cooperation scheme can effectively improve the achievable throughput in the WPCN with desired user fairness.The authors are with the

Multi-antenna Enabled Cluster-based Cooperation in Wireless Powered Communication Network

“…[7] and [8] allow the two users to exchange their information and form a distributed antenna system to transmit their information jointly. [11] further considers a general multiple user scenario, where a far-away user's transmission is assisted by multiple WDs.…”

“…However, such design may lead to a doubly near-far unfairness problem that WDs far-away from HAP achieve low throughput because they harvest less energy and consume more to transmit information. To improve throughput fairness, different user cooperation methods are proposed [7,8,10,11]. For instance, [10] proposes a two-user cooperation, where the nearby user acts as a relay to forward the transmission of far-away user to the HAP.…”

Backscatter Communication for Wireless-Powered Communication Networks

“…Also, authors in [3] presented user cooperation to alleviate the doubly-near far problem. It has been shown that a near user first helps relay information of a far user to the H-AP and then uses the remaining time as well as energy to transmit its own information for more balanced throughput with desired fairness.…”

“…However, the only two-user case has been analyzed in [3] and the proposed cooperation protocol with undue complexity may not be feasible for large-scale wireless sensor networks.…”

“…Backscatter communication for WPCNs can help to increase the coverage of such network and diminish the signal-to-noise ratio (SNR) outage zone, compared to the active radio based WPCNs [2,3] .…”