  In this paper, we jointly optimize computation offloading and resource
allocation to minimize the weighted sum of energy consumption of all mobile
users in a backhaul limited cooperative MEC system with multiple fog servers.
Considering the partial offloading strategy and TDMA transmission at each base
station, the underlying optimization problem with constraints on maximum task
latency and limited computation resource at mobile users and fog servers is
non-convex. We propose to convexify the problem exploiting the relationship
among some optimization variables from which an optimal algorithm is proposed
to solve the resulting problem. We then present numerical results to
demonstrate the significant gains of our proposed design compared to
conventional designs without exploiting cooperation among fog servers and a
greedy algorithm.
