Motorola CP02 Introduction to Digital Cellular (E-Book)

Global System for Mobile Communications (GSM) is a digital cellular communications technology based on Time Division Multiple Access (TDMA), and is the dominant mobile communications system in most of the world, including Europe, the Middle East, Africa, and Asia, and it now has a strong presence in North America as well. First introduced in 1991, the GSM standard has been deployed in four different frequency bands: 800 (called "850" so as not to be
confused with D-AMPS on 800), 900, 1800, and 1900 MHz. GSM 850 and 1900 are primarily used in North America; GSM 900 and 1800 are primarily used outside of North America. GSM uses narrowband TDMA that allows up to eight (or sixteen with Half-Rate Codec) simultaneous calls on the same radio frequency using different time slots in the same channel. Along with CDMA and D-AMPS (Digital AMPS, often referred to simply as "TDMA"), GSM represents the 2nd generation (2G) of cellular wireless.
For more detail, download CP02 Introduction to Digital Cellular of Motorola.