Summary

28 IT Essentials: PC Harware and Software Companion GuideThe first generation (1G) of cell phones began service in the 1980s. First-generation phonesprimarily used analog standards, including Advanced Mobile Phone System (AMPS) andNordic Mobile Telephone (NMT).In an analog system, the voice information is sent by varying the radio signals used by thephone in the same pattern as the speakers’ voices. Unfortunately, this means that interferenceand noise, which also vary the signal, cannot easily be separated from the voice in thesignal. This limits the usefulness of analog systems.Digital signals convert the speakers’ voices into a digital signal that uses a chain of 1s and0s. This degrades the signal a little, because 1s and 0s are not a faithful representation ofyour voice. However, the digital signal is robust. It can be fixed using error correction routinesif there is interference. Also, digital signals can be compressed, making the systemsmuch more efficient than analog systems.In the 1990s, the second generation (2G) of cell phones was marked by a switch from analogto digital standards. Second-generation cell standards included Global System forMobile (GSM), Integrated Digital Enhanced Network (iDEN), and Code Division MultipleAccess (CDMA).Third-generation (3G) standards enable cell phones to go beyond simple voice and datacommunications. It is now common for cell phones to send and receive text, photos, andvideo. It is also common for 3G cell phones to access the Internet and to use the GlobalPositioning System (GPS).NoteAs 3G cell phone standards were being developed, extensions to the existing 2G standards wereadded. These transitional standards are known as 2.5G standards.Fourth-generation (4G) standards have been championed by many users because of theavailability of increased data rates. Higher data rates will allow users to download files,such as video and music, faster than what was available with standards of previous generations.Table 6-6 shows more information about the different cell phone standards.Table 6-6Cell Phone StandardsGeneration Standard Name Features Used In1G Nordic Mobile Replaced wired Saudi Arabia,(Analog cell Telephone (NMT) telephones Scandinaviaphone standardsintroduced inthe 1980s)Advanced Mobile Replaced wired United States, NewPhone System (AMPS) telephones Zealand