d in this book. Some important parameters for technology analysis are discussed in the following. Transmission Rate An important technological parameter in evaluating telecommunications systems is transmis- sion rate or the speed by which messages may be transferred. This depends on the medium used for transmission, signal and noise power as well as the medium 'bandwidth' which determines the amount of data that can be sent at any time interval. For example, a horse-mounted courier's travelling speed and the total number of messages (written on baked clay or paper) a courier can carry are limited. Clearly two couriers can carry twice as many messages: this can be consid- ered as doubling the capacity of the system through doubling the (band) width of the channel. Technology, Business and Policy Table 2.1 Maximum transmission rates for commonly used telecommunications systems Telecommunications system Transmission rate (peak) Wireless - 3G 10s of Mbps Wireless - 4G 100s of Mbps GEO satellite Several Mbps LEO satellite Several Mbps 100s of Mbps Optical fibre >1 Gbps Modern telecommunications use electromagnetic waves to transmit signals over a number of different media including air, copper wires and optical fibres. Electromagnetic waves travel at, or close to, the speed of light depending on the media. This speed determines the propaga- tion delay, or the time it takes for one symbol of the total message to traverse the medium between a transmitter and a receiver. The maximum amount of information that can be carried per second, as will be shown in Chapter 4, is a function of signal bandwidth or spectrum - in essence the size of the pipe that carries data. All telecommunications media have a limited bandwidth for transmission because of physical or regulatory constraints. (For example, a copper wire has characteristics that limit the bandwidth that may be used for transmission of data; or in the case of wireless communi- cations, mobile operators have access to a limited spectrum.) The wider the pipe is, the more 