emes such as AVC provide a partial solution to this but increase error and jitter sensitivity. Similar constraints apply to MPEG4 coding schemes. A 36-MHz satellite transponder capable of supporting 25 standard definition TV programs will be hard pressed to support more than 5 or 6 HDTV channels. Terrestrial TV Terrestrial TV has a significant advantage over satellite in that it is potentially neither power nor bandwidth limited. The need to coshare spectrum with analogue transmissions has required digital TV to transmit at suboptimum power levels, but this constraint disappears once analogue transmissions are switched off. There are obvious opportunities to increase signal strengths over and above present analogue TV transmissions by increasing the number of DVB transmission sites. Cellular operators are natural partner in this process. This opens up the possibility of supporting a wider range of portable and mobile devices including the use of these devices within buildings. It could of course be argued that in building portable and mobile device applications can also be serviced by a combination of fibre, cable or copper access combined with WiFi. However, it would be economically hard for any alternative delivery options (including mobile broadband Table 2.7 DVB-S Data rates Definition Data rate Data rate with AVC coding 4.4 Mbit/s 2.2 Mbit/s 18 Mbit/s 9 Mbit/s Making Telecoms Work and/or possible future combined WiFi/mobile broadband networks) to match the ability of terrestrial TV to deliver a 20-Mbit or 30-Mbit downlink to devices irrespective of where or how they are being used. Discussions are ongoing as to how much of the UHF bandwidth terrestrial broadcasters retain after the analogue to digital switchover is complete. Even if the cellular industry took 100 MHz of digital dividend spectrum there would still be 300 MHz available to support a broad range of national and local standard and high-definition TV multiplex options. Terrestrial TV therefore has a significant role to play in the standard and hig