re observed worldwide, and that creates interoperability problems. Addressing the growing need for data communications in Internet access and, in fact, the buildout of a wireless Internet requires developments on all the standards fronts. The following sections describe the major 2G standards. Chapter 14 Wireless WANs The Difference Between Cellular and PCS Cellular is classified as including both analog and digital networks. Cellular networks started out as analog, and they migrated to digital infrastructures. Cellular operates in the 800MHz to 900MHz band, depending on where you are in the world. Cellular tends to operate in macrocells, which involve a coverage area with a diameter up to 8 miles (12.8 km), and because of the large coverage area, the power utilization is high, ranging from 0.6 to 3 watts. PCS is a newer introduction than cellular, and it has been digital from the start. It operates in the 1.8GHz to 2GHz band, again depending on where you are in the world. It uses both microcell and picocell architectures, which means the coverage areas are quite small, around 1 mile (1.6 km) in diameter, and because the coverage area is small, much lower power is used-100 milliwatts or so. Functionally, cellular and PCS work the same way, they perform the same functions, and they use the same types of network elements. The key differences between them are the frequencies at which they operate, their coverage areas, and the power levels they use. One of the most popular of the digital cellular standards is Global System for Mobile Communications (GSM), which was first deployed in 1992. GSM is the technology that underpins most of the world's mobile phone networks. The GSM platform is a hugely successful wireless technology and an unprecedented story of global achieve- ment and cooperation. GSM has become the world's fastest-growing communica- tions technology of all time and the leading global mobile standard. As of January 2006, there were 670 commercial GSM networks operating in more than 210 coun- tries/territ