conditions options, can not have the distances (100 This reduces potentially deliver legacy reach of metres) - a fully capacity and terabits of data copper in most amortised sunk incurs a higher bit developed investment error rate but lots markets of user functionality Physical Layer Connectivity account, if an analysis was done on the amount of video and audio consumed over wireless and comparison made with the amount of video and audio delivered uniquely over an end-to-end guided media delivery route then it would be obvious that this switch has not occurred in any meaningful way. Partly this is because terrestrial TV has far from disappeared. As we shall see later in Chapter 15 both the European and Asian terrestrial broadcasting community and US terrestrial broadcasters are actively developing portable TV standards that by definition guided media cannot match. Additionally in the mobile domain there are now nearly six billion mobile users who expect to consume media on the move or at least in an untethered nomadic environment SO what has actually happened is that consumption has increased in all domains rather than transferred from one domain to another. Technology has therefore not taken us in the direction expected by the visionary pundits fifteen years ago. One explanation for this is that over the past ten years guided and unguided media data rates have, by and large, increased in parallel. However, our ability to manage and mitigate and to an extent exploit the variability of radio channels, particularly bidirectional radio channels with two-way signalling capability, has increased rather faster. 2.3 The Cost of Propagation Loss and Impact of OFDM All types of guided transmission media suffer propagation loss to a greater or lesser degree, but that loss is predictable and largely nonvariant over several orders of time scale. For example, a one-kilometre length of fibre, cable or copper will have defined loss characteristics that will stay stable over seconds, hours, days, months and years. Unguided media