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To engineer any telephone system, wireless or landline, we need some way of estimating telephony demand and criteria for satisfying that demand. Traffic engineering is the process of assigning facilities to satisfy a demand. Traffic engineering is particularly important inside the public switched telephone network (PSTN), the Internet, the cellular backhaul network, and other networks where demand from multiple users is carried over shared channels. Statistical methods can be applied to estimate demand and design facilities to meet peak demand. In this chapter we will explain those methods. First, we will look at the methods traditionally used in telephony, which assumed that all circuits were the same size and that the average length of telephone calls was unlikely to change very much.
Our results show that call capacity is most likely constrained by network devices rather than physical connections. Therefore, we recommend considering both packet throughput and bit throughput (bps) in determining the max call load. If network capacity is constrained by packet throughput, codec schemes would have almost no effect on the maximum call load.