Joint Optimization on Both Routing and Resource Allocation for Millimeter Wave Cellular Networks

Due to the spectrum scarcity issue in conventional cellular networks, millimeter-wave ( mmWave) technology has been proposed and is expected to be used in small cells to meet the requirements for spectrum resources, especially for those small cells that are densely deployed and form a multi-hop backhaul structure. For this novel architecture, a cross-layer optimization problem aiming at maximizing the energy efficiency while taking into account both the route selection and resource allocation is formulated. To find the optimal solution, we first decouple the original problem into a resource allocation sub-problem at the link-physical layer and a route selection sub-problem at the network layer. Since the resource allocation sub-problem at the link-physical layer is a non-convex problem and NP-hard, we apply stochastic algorithms to search for the optimal solution. Since the network layer sub-problem is simplified as a linear programming problem, an LP solver is applied to optimize energy efficiency. To reflect the interplay between these two problems, we further propose two joint optimization strategies. One uses stochastic algorithms that are composed of four schemes with given routes for resource allocation and linear programming for the route selection based on the given resource allocation. The other uses the linear programming to evaluate the fitness of each individual in the stochastic algorithms. The simulation results reveal the following: 1) our proposed schemes are capable of finding near-optimal solutions and can improve the energy and spectrum efficiency; and 2) properly finding the route without overloading any one of the base stations is capable of improving the throughput of the networks.