11Heterogeneous Networks

As indicated in the description of the generic network model presented in Chapter 1, future networks will be heterogeneous and will use massive offloading opportunities from cellular network to WLAN and femto/small cells. For this reason in this chapter we discuss the fundamentals of that technology.

11.1 Preliminaries

Due to the high cost of network extension via macro base stations (MBSs), small cells at the moment are envisioned as a key solution to accommodate the rapidly growing user population and the associated traffic load [2]. Small cells provide a fast, flexible, cost-efficient, and customer-oriented solution for cellular service providers. The term small cell refers to low-powered radio access nodes that have a transmission range of several tens to several hundreds of meters and include femtocells, picocells, microcells, and metrocells.

A multitier network where small cells are overlaid on macrocells is generally referred to as a heterogeneous network (HetNet). Overlaying the MBSs with small cells introduces a substantial shift in the cellular infrastructure such as topological randomness and high variability in the specifications (transmit power, supported data rate, etc.) of the coexisting network entities. Therefore, the techniques for modeling and optimization of legacy cellular wireless networks, and algorithms for different network functions (e.g., power control, admission control, resource allocation) should be revisited and adapted ...

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