Optimal Broadcast Scheduling for an Energy Harvesting Rechargeable Transmitter with a Finite Capacity Battery

• Published in: IEEE transactions on wireless communications Vol. 11; no. 6; pp. 2193 - 2203
• Main Authors: Ozel, O., Jing Yang, Ulukus, S.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.06.2012; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Batteries; broadcast channels; Data communication; Energy harvesting; Exact sciences and technology; finite-capacity battery; Minimization; Phase change materials; Radiocommunications; Receivers; rechargeable wireless networks; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; throughput maximization; Transmission and modulation (techniques and equipments); transmission completion time minimization; Transmitters; Transmitters. Receivers; Availability; Overflow(computer arithmetics); Performance evaluation; transmission completion time minimization; throughput maximization; Wireless telecommunication; Information rate; Transmitter; Data transmission; Secondary cell; Energy harvesting; Algorithm; Information transmission; Transmission time; AWGN channels; finite-capacity battery; Storage capacity; rechargeable wireless networks; Broadcast channels; Off line; Wireless network; Optimal planning
• ISSN: 1536-1276
• DOI: 10.1109/TWC.2012.032812.110813

We consider the minimization of the transmission completion time with a battery limited energy harvesting transmitter in an M-user AWGN broadcast channel where the transmitter is able to harvest energy from the nature, using a finite storage capacity rechargeable battery. The harvested energy is modeled to arrive (be harvested) at the transmitter during the course of transmissions at arbitrary time instants. The transmitter has fixed number of packets for each receiver. Due to the finite battery capacity, energy may overflow without being utilized for data transmission. We derive the optimal offline transmission policy that minimizes the time by which all of the data packets are delivered to their respective destinations. We analyze the structural properties of the optimal transmission policy using a dual problem. We find the optimal total transmit power sequence by a directional water-filling algorithm. We prove that there exist M-1 cut-off power levels such that user i is allocated the power between the i-1st and the ith cut-off power levels subject to the availability of the allocated total power level. Based on these properties, we propose an algorithm that gives the globally optimal offline policy. The proposed algorithm uses directional water-filling repetitively. Finally, we illustrate the optimal policy and compare its performance with several suboptimal policies under different settings.