 tion of the system commenced. outline below, but in addition special mention must be made of the AMPS is in operation extensively across the north American European designed GSM system which is set to become the domi- continent (USA and Canada). Due to the regulatory conditions in nant standard for Europe in the mid to late 1990's. force in the USA, deployment has been in the form of a patchwork of largely independent standalone systems, with two competing 47.4.1 systems operating in each licence area. Although commercial roam- ing agreements exist to allow customers of one operating company to obtain service from another when they are in a different part of AMPS stands for Advanced Mobile Phone System and was de- the country, a seamless nationwide service is, as yet, not available veloped in the USA primarily by Bell Laboratories as a successor to the customer. for the heavily congested IMTS (Improved Mobile Telephone Sys- AMPS is now also used in a number of a number of central and tem). Being designed for the north American market, AMPS uses south American countries, in Australia and some far east countries. the 800MHz band allocated to mobile services in ITU Region 2 (the World-wide it is the dominant standard in terms of installed cus- Americas), with 30kHz channel spacing in common with estab- tomer base. lished PMR practice. AMPS is being further developed to incorporate digital speech AMPS uses analogue FM for speech transmission, but with a encoding, with TDMA techniques to give three digital voice chan- wider frequency deviation (12kHz) than is the norm for a 30kHz nels per one radio channel. Digital AMPS (DAMPS) has the same channelling system. By adopting the wide deviation, the dynamic basic architecture and signalling protocol as AMPS and is therefore range of the speech channel is extended and protection against more evolutionary than revolutionary (as is GSM in Europe). co-channel interference is increased. This, together with the use of speech compression/expansion (companders) yields a high qua