cations is passed to the European Telecommunications Standards Institute (ETSI). Phase 1 of the GSM specifications is delivered. Commercial launch of the GSM service occurs. The addition of the countries that signed the GSM Memorandum of Under- standing takes place. Coverage spreads to larger cities and airports. Coverage of main roads GSM services starts outside Europe. Phase II of the GSM specifications occurs. Coverage is extended to rural areas. mobile telecommunications. 1 GSM truly stands for Global System for Mobile telecommunications. Roaming is the ability to use your GSM phone number in another GSM network. You can roam to another region or coun- try and use the services of any network operator in that region that has a roaming agreement with the GSM network operator in your home region/country. A roaming agreement is a business agreement between two network operators to transfer items such as call charges and subscription information back and forth as their subscribers roam into each other's areas. 1 As of May 2001 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Introduction to GSM Introduction to GSM GSM Metrics The GSM standard is the most widely accepted standard and is imple- mented globally, owning a market share of 69 percent of the world's digital cellular subscribers. TDMA, with a market share close to 10 percent, is available mainly in North America and South America. GSM, which uses a TDMA access, and North American TDMA are two of the world's leading digital network standards. Unfortunately, it is currently technically impos- sible for users of either standard to make or receive calls in areas where only the other standard is available. Once interoperability is in place, users of GSM and TDMA handsets will be able to roam on the other network type -subject to the agreements between mobile operators. This will make roami