10.1 Introduction

Chapter 9, "3G System RF Design Considerations," addressed the RF design issues related to the implementation of a 3G network. This chapter focuses on the design of the non-RF aspects of the network. Thus, we consider issues such as placement and dimensioning of Mobile Switching Centers (MSCs), Base Station Controller (BSC), Serving GPRS Support Node (SGSN), Packet Data Serving Node (PDSN), and so on. We also address the connectivity and transport requirements between the various network elements.

In general, the design of the core network involves striking a balance between three requirements meeting or exceeding the capacity needed to handle the projected demand; minimizing the capital and operational cost of the network; and ensuring high network reliability/availability. In short, we can refer to these three issues as cost, capacity, and quality. Of course, meeting one or more of the requirements often means making sacrifices elsewhere such that it is impossible to divorce one network design consideration from any of the others. For example, a lower cost might well mean a lower network capacity or a lower network quality. Thus, we will never get a network that is remarkably cheap to implement and operate while still offering high capacity and high quality. Instead, we must aim to establish some "happy medium" where we satisfy at least the most important criteria.

10.2 Traffic Forecasts

Obviously, we need to design a network that will support the projected traffic demand. Consequently, projecting subscriber usage is a critical...