Radio Resource Management in Multi-Tier Cellular Wireless Networks

CHAPTER 4

RESOURCE ALLOCATION FOR CLUSTERED SMALL CELLS IN TWO-TIER OFDMA NETWORKS

4.1 INTRODUCTION

As we have discussed before, in an OFDMA-based two-tier cellular network with spectrum sharing among small cells and macrocells, co-tier interference and CTI significantly affect network performance [1]. Hence, interference mitigation techniques need to be developed to manage the radio resources of small cells in order to achieve the QoS requirements of all the users. In this chapter, we study the problem of sub-channel and power allocation in a dense deployment of femtocells in an OFDMA-based two-tier network with constraints on co-tier interference and CTI as well as minimum data rate requirements. We formulate the problem of joint sub-channel and power allocation for a clustered femtocell network with interference constraints on co-tier interference and CTI as well as data rate constraints as an optimization problem. The optimization problem aims at maximizing the sum-rate of the femtocells in a cluster of cooperating femtocells. This problem turns out to be a Mixed Integer Non-Linear Program (MINLP). Therefore, to solve this problem sub-optimally, different approaches are proposed. The first approach works by reformulating the MINLP problem as a convex one by using the time sharing idea, where sub-channels can be time shared among femtocells. Joint sub-channel and power allocation using the reformulated problem gives an upper bound to the original problem. In the other approaches, ...