Delay-optimal multi-flow buffered decode-and-forward relay communications with limited renewable energy storage

Abstract

In this paper, we consider the delay minimization for multi-flow buffered decode-and-forward relay communications with renewable energy source, where the transmit power of the source nodes and the relay node is contributed by both the conventional AC utility power and the renewable power.We formulate the delay-optimal resource control problem as an infinite horizon average cost Constrained Markov Decision Process. By exploring the special problem structure, we shall derive an equivalent Bellman equation based on a reduced state space. Using a fluid approximation approach, we derive the power, rate and link selection policy which is asymptotically optimal for small slot durations. We further propose a distributed online learning algorithm to estimate the per-flow value functions as well as the Lagrange multipliers. We establish the technical proof for the almost-sure convergence of the proposed learning algorithm. By simulation, we show that the proposed scheme can achieve substantial delay performance gain compared with various conventional baseline protocols.

Distributed Power Control for Delay Optimization in Energy Harvesting Cooperative Relay Networks

“…The systematic way to account for buffer-aided relaying is again a formulation based on stochastic dynamic programming; however, in order to come up with a realistic scalable solution, we need to take on a different approach for problem decomposition. There are some studies along this line (e.g., see [17]) which address delay optimization in the context of buffer-aided relaying by exploiting the structural properties inherent to the problem.…”

“…Finally, in [17], a multi-source, single relay cooperative network is considered where the traffic at the source nodes is assumed to be bursty and the forwarding protocol used by the relay is DaF. The transmit power of all nodes is assumed to be contributed by both the conventional AC utility power and the renewable energy.…”

“…Also, the existing online schemes require explicit knowledge of the statistics of the system processes [9,10,11,19] and do not address the case of bursty traffic in general where the optimization of the queueing delay is necessary. Unlike [17], in this paper, we consider an EH cooperative relay system consisting of multiple AaF relays 0018-9545 (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.…”

“…Exploiting both energy harvesting and cooperative communications has received a considerable interest recently [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The use of EH relays in cooperative communication was first introduced in [8], where a comprehensive performance analysis was conducted for relay selection and transmission power setting in an AaF network in terms of symbol error probability by using a probabilistic energy model.…”

“…More recently, several studies have come up with transmission control strategies (e.g., power allocation, relay selection, etc.) to optimize different network utility functions in EH relay systems [7,9,10,11,13,14,15,17,18,19,20,35]. These schemes can be categorized based on two main distinguishing features:  Optimization method (offline/online/learning-theoretic): In offline optimization, it is assumed that all the future realizations of data/energy arrivals as well as the channel variations are known acausally before the system starts.…”