Optimal Resource Allocation for Multi-User MEC with Arbitrary Task Arrival Times and Deadlines

In this paper, we investigate the optimization of task operation sequences for designing practical multi-user mobile edge computing (MEC) systems. First, we consider a computation task model with non-negligible sizes of computation results and arbitrary task arrival times and deadlines. Based on it, we further establish a computation offloading model considering non-negligible executing durations, allowing parallel transmissions and executions for different tasks, and reflecting the impact of task operation sequences. Then, we formulate the weighted sum energy consumption minimization problem to optimize the task operation sequences and starting times for uploading, executing and downloading as well as uploading and downloading time durations. The problem is a challenging mixed discrete-continuous optimization problem. By analyzing structural properties of task operation sequences, we develop an algorithm to obtain an optimal solution. In addition, using several optimization techniques, we transform the problem to an equivalent Difference of Convex (DC) problem, and develop a low-complexity algorithm to obtain a suboptimal solution using Penalty Convex Concave Procedure (CCP). Finally, numerical results demonstrate the advantages of the suboptimal solution over some optimized schemes with typical choices for task operation sequences.