Resource Allocation and Performance Study for LTE Networks Integrated with Femtocells

Abstract

Long-Term Evolution (LTE) networks comprising conventional cellular macrocells plus user-installed femtocells offer an economically viable solution to achieving high user capacity and upgrading to future fourth-generation systems. With the growing impetus for frequency reuse, the capacity of each user depends on not only the power spectral density of its own, but also on those of others in neighboring cells. Mitigating interference among macrocells and femtocells requires allocating physical resource dynamically in response to channel conditions. In this paper, we formulate the resource allocation problem as a utility optimization and develop a distributed algorithm for joint power control and user scheduling. The algorithm makes novel use of a class of fairness measures for determining user scheduling and is shown to be very efficient for realistic network parameters. Additionally, using a practical model for the LTE air interface that captures geographic distribution of users and buildings, we provide for a framework that allows comparison of different resource allocation algorithms. A variety of problem formulations, including femtocell density, resource tradeoff, and complexity-optimality tradeoff are derived and analyzed using a geometry-based stochastic LTE air interface model. Our analysis also offers useful guidelines for the planning and design of macrocells and femtocells.