 data communications systems. User-network transmission delay is generally a factor of speed of electromagnetic wave propagation. It is also a function of data frame structure and control mechanism of a technology. End-to-end delay is a significant parameter as it may mean that some services cannot be accommodated. For example, voice communications requires a 200-300 ms end-to-end delay to ensure con- versations can be conducted naturally. Some applications such as email and web-browsing may not be SO sensitive to delay, but other applications such as computer games require short delays in the order of a few milliseconds. With the exception of satellite communications, infrastructure layer delay is generally small and of little consequence, although protocol delay as data is packetized can impact delay- sensitive applications (such as high frequency trading or peer-to-peer gaming). On the other hand, retail layer companies relay data from service/content layers and their backhaul links and processing capability can cause delay and reduce QoS. Another important metric is perceptual quality of sound and video. These are usually functions of transmission rate as well as the probability of lost data. Source coding techniques also contribute to the reproduction quality of streaming media. Different broadband telecom- munications systems are impacted equally by these factors, although the transmission rates each technology offers lead to variations in perceptual quality. Business Issues A business may be characterised by its cost and revenues. In telecommunications businesses costs are due to network and infrastructure design and build-up - referred to as capital expenditure (CAPEX); and customer acquisition and service, and equipment maintenance - known as operational expenditure (OPEX). Benefits or revenues come from fees paid by end-users/subscribers A cash flow analysis for a typical business in the broadband telecom- munications field is shown in Figure 2.8 [7]. While the cash flow principles equally apply to all 