Stochastic Buffer-Aided Relay-Assisted MEC in Time-Slotted Systems

Mobile Edge Computing (MEC) is a promising paradigm to respond to the rising computation requests of the users in the emerging wireless networks, and especially in the Internet of Things (IoT). In this paper, we study buffer-aided relay-assisted MEC in systems with discrete transmission time-line and block fading channels. We consider a hierarchical network composed of a source, a buffer-aided relay, and another node in a higher level in the hierarchy. The source sends its tasks to the relay which in turn randomly assigns the received tasks to its own computing server or to the server of the next node in the hierarchy. We provide a framework to take into account the delays in both the transmission and computation buffers which facilitates the derivation of the expression for the Average Response Time (ART) in the system. Based on that and the system average power consumption in each slot, we introduce the concept of Average Response Energy (ARE) as a novel metric to capture the energy efficiency in MEC. Accordingly, we propose two offloading schemes with relevant problem formulations, namely the Minimum ART (MART) and the Minimum ARE (MARE) schemes, to optimize the ART or the ARE while keeping the system queues stable. We analyze the properties of the formulated problems, in terms of the feasible sets and the objective functions and noting them, we propose effective solution methods. Using extensive simulations, we validate the presented analysis and show the effectiveness of the proposed schemes in comparison with various baseline methods.