Heterogeneous Cellular Networks

6

Cognitive Radios to Mitigate Interference in Macro/femto Heterogeneous Networks

Shin-Ming Cheng1 and Kwang-Cheng Chen2

1National Taiwan University of Science and Technology, Taiwan

2National Taiwan University, Taiwan

6.1 Introduction

Heterogeneous network (HetNet) deployment [1,2], where low-power and small-coverage local nodes are distributed in the coverage of a macro node, is considered as a promising solution to achieve universal frequency reuse. The local nodes such as pico, femto and relay nodes deployed at coverage holes could extend coverage and increase spectral utilization. Moreover, the small coverage area of local node facilitates a large number of concurrent transmissions and improves spatial reuse, thereby potentially yielding enhanced wireless capacity. When all heterogeneous nodes share the same spectrum, two kinds of interference appear:

Cross-tier interference. The aggressor (e.g., a local node) and the victim of interference (e.g., a macro node user) belong to different tiers.

Intra-tier interference. The aggressor (e.g., a local node) and the victim (e.g., a neighbouring local node user) belong to the same tier.

Under the impact of interference, some resource blocks (RBs) can not be utilized simultaneously, which challenges HetNet toward universal frequency reuse. Thus, interference mitigation in HetNet receives much attention in both areas of academic and industry [3–5]. Typically, interference mitigation techniques are classified into following two categories ...