On Multiuser Resource Allocation in Relay-Based Wireless-Powered Uplink Cellular Networks

Abstract

We propose relay-based wireless-powered uplink cellular networks in which users first harvest energy from RF transmissions of base station/relay nodes and then use that energy for uplink transmission. Given the limited total transmission time and available energy at the relay node, we propose different resource allocation frameworks for the proposed relay-based networks considering two different relay-based harvest-then-transmit scenarios. We first propose iterative algorithm to determine time and relay node power allocation (for downlink wireless charging and uplink data transmission/relaying) for both scenarios. We then perform joint optimal time and power allocation for one scenario. Resource allocation results show that most of the available resources (transmission time and relay node energy) are allocated for wireless energy harvesting which is similar to that observed for downlink simultaneous wireless information and power transfer (SWIPT) in the existing literature. Simulation results on comparison of different relay-based scenarios reveal interesting insights and demonstrate remarkable improvement of different performance metrics of wireless-powered cellular networks in the presence of relay node.

Energy Efficiency Optimization For Wireless Powered Sensor Networks With Nonorthogonal Multiple Access

“…In [7], the well-known "harvest-then-transmit" protocol was proposed, where the time allocated to the hybrid access point (H-AP) for downlink WET and the time and transmit power allocated to the sensors for uplink WIT were jointly optimized for system throughput maximization. Since then, related works have been extensively done in the context of WPSNs with relays [8], [9], full-duplex radio [10], [11], cognitive radio [12]- [15], MIMO [16]- [18] and nonorthogonal multiple access (NOMA) schemes [19]- [21]. However, the above works only focus on the spectrum efficiency of WPSNs, which may lead a great dissipation of energy during the downlink WET.…”

Joint wireless information and energy transfer in cache-assisted relaying systems

“…At the relay, the time switching (TS) scheme is employed so that the received signal is first provided to the the energy harvester for some fraction of the time allocated for transmitter-relay communication link, and then to information decoder for the remaining fraction. This type of mechanism is also referred in literature as harvest-then-forward protocol [20].…”

“…Case VII: λ 1 = 0 =⇒ G(θ, φ, P R ) = 0; λ 2 = 0 =⇒ H(θ, φ, P R ) = 0; λ 3 = 0 =⇒ I(θ, φ, P R ) = 0 From (20) and 21 Since the solution of (34) is composed of complex values, therefore this case is not acceptable.…”

Dilemma at RF Energy Harvesting Relay: Downlink Energy Relaying or Uplink Information Transfer?

“…Furthermore, energy cooperation and sharing strategies have been proposed in [11], [12] to overcome dynamics of ambient energy harvesting and enable perpetual operation. In another set of works [13]- [15], R e l a y i n g P h a s e 1 ( b ) : E n e r g y R e l a y i n g relay-powered communications was considered, where energysufficient relay transfers energy to RF harvesting nodes.…”

“…In recent studies, harvested energy at relay is either used for energy relaying (ER) [5] or IR [6]- [10], [16]- [20]. Though [13]- [15] studied tradeoff in ET and IR efficiency assuming energy-rich relay, these works along with [11], [12] did not investigate RF harvesting relay assisted ER possibilities. This work fills this existing research gap.…”