HSPA+ Evolution to Release 12: Performance and Optimization

7 Heterogeneous Networks

Harri Holma and Fernando Sanchez Moya

7.1 Introduction

Heterogeneous Network (HetNet) refers to the joint optimization of different cell layers and technologies. Current mobile networks are based on wide area macro cells that provide several hundred meters of coverage, even tens of kilometers, and normally use three sectors per site. Small cells can be added to provide more capacity and coverage. These small cells can be outdoor small cells, public indoor small cells, or home or enterprise small cells. The outdoor small cells are often termed micro cells, indoor cells pico cells, and home small cells femto cells. The HetNet concept is shown in Figure 7.1.

Figure 7.1 HetNet concept

The HetNet concept also considers the use of the different technologies GSM, HSPA, LTE, and WLAN together. This chapter focuses on HSPA small cell deployments together with existing macro cells on WLAN interworking. Section 7.2 presents the drivers for the small cell rollouts. Section 7.3 shows the base station categories. Sections 7.4 and 7.5 present the main challenges with HSPA HetNets – interference management and link imbalance, Section 7.6 studies the data rate and capacity benefits provided by the small cells, and Section 7.7 illustrates field deployment result with HSPA small cells. Femto cell architecture and optimization are discussed in Section 7.8 and WLAN interworking ...