Abstract
A wireless powered communication network (WPCN) is considered, which has a hybrid access point (H-AP) and two users with energy harvesting capabilities. The H-AP transfers energy to the users during downlink (DL) transmission, and the users transmit information to the H-AP during uplink (UL) transmission by utilizing the harvested energy. To enhance user fairness, a user cooperation protocol is employed in which a user close to the H-AP relays the message of the other user by partially using its allocated time and available energy resources. By jointly optimizing the time allocation for DL energy transfer and UL information transmission, we maximize the sum-throughput in the considered network subject to a set of quality of service (QoS) requirements. The optimization problem is solved through a divide-and-conquer approach along with convex optimization techniques, and thus an analytical solution is derived. In particular, the conditions under which the WPCN benefits from the user cooperation in achieving the maximum sum-throughput are fully characterized. Furthermore, an efficient resource allocation algorithm to find the optimal solution under QoS requirements is presented.
Highlights
W IRELESS energy harvesting has recently attracted a significant amount of attention for the generation communication systems as it is expected to prolong the lifetime of wireless networks delivering self-sustainability without manual battery recharge or replacement [1], [2]
Wireless powered communication networks (WPCNs) have emerged as a new framework to the design of wireless networks, which consist of a hybrid access point (H-AP) with external power supply and wireless devices with no energy source, but rechargeable batteries [9]
In [9], a harvest--transmit protocol was proposed in which wireless devices are powered from RF signals radiated from a H-AP via the downlink (DL), called wireless energy transfer (WET), which send information using the harvested energy via the uplink (UL), called wireless information transmission (WIT)
Summary
W IRELESS energy harvesting has recently attracted a significant amount of attention for the generation communication systems as it is expected to prolong the lifetime of wireless networks delivering self-sustainability without manual battery recharge or replacement [1], [2]. Many attempts have been made to alleviate the user unfairness in WPCNs [9], [12], [13], [22]- [23], etc One of these approaches is to maximize the minimum rate among the users by the joint design of DL-WET and UL-WIT, thereby a user far from the H-AP can be allocated with more time to transmit information [9]. The WST maximization has high computational complexity as it searches the optimal point numerically by jointly optimizing the primal and dual problems In this regard, we formulate a new sum-throughput maximization problem under individual QoS constraints on user throughputs with user cooperation and provide the optimal solution in an analytical form.
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