s were called cell phones. All the systems that were initially developed were quite incompatible with each other. Each of these networks implemented their own standards. Facilities such as roaming within the continent were impossible and most countries had only one operator. The penetration was also low; e.g. penetration in Sweden was just 7 %, while countries like Portugal had a penetration of only 0.7%. Handsets were also expensive, the minimum being more than $1000. Apart from higher costs and incompatibility with other cellular networks, first generation technology also had an inherent limitation in terms of channels, etc. 1.2.1 NMT (Nordic Mobile Telephony) The NMT mobile phone system was created in 1981 as a response to the increasing congestion and heavy requirements of the ARP (auto radio puhelin, or car radio phone) mobile phone network. The technical principles of NMT were ready by 1973 and specifications for base stations were ready in 1977. It is based Advanced Cellular Network Planning and Optimisation Edited by Ajay R Mishra © 2007 John Wiley & Sons, Ltd Cellular Networks on analogue technology (first generation or 1G) and two variants exist: NMT 450 and NMT 900. The numbers indicate the frequency bands used. NMT 900 was introduced in 1986 because it carries more channels than the previous NMT 450 network. The NMT network has mainly been used in the Nordic countries, Baltic countries and Russia, but also in the Middle East and in Asia. NMT had automatic switching built into the standard from the beginning. Additionally, the NMT standard specified billing and roaming. The NMT specifications were free and open, allowing many companies to produce NMT hardware and pushing prices down. A disadvantage of the original NMT specification is that traffic was not encrypted. Thus, anyone willing to listen in would just have to buy a scanner and tune it to the correct frequency. As a result, some scanners have had the NMT bands 'deleted' SO they could not be accessed. This is not particularly effective as it is 