3G and Beyond
CDMA and TDMA CDMA ( Co de- D ivision M ultiple A ccess ) a digital cellular technology that uses spread-spectrum techniques. Unlike systems that use TDMA, CDMA does not assign a specific frequency to each user. Instead, every channel uses the full available spectrum. Individual conversations are encoded with a pseudo-random digital sequence. TDMA (Time Division Multiple Access) a technology for delivering digital wireless service using time division multiplexing. TDMA works by dividing a radio frequency into time slots and then allocating slots to multiple calls. In this way, a single frequency can support multiple, simultaneous data channels. TDMA is used by the GSM digital cellular system.
1G (Analog) Uses frequency division multiple access (FDMA) to communicate (every call in one area uses its own set of channels for communication) No support for wireless data NMT (Nordic Mobile Telephone) is an analog cellular phone system deployed in more than 40 countries in Europe. NMT was the first analog cellular phone system. The system used originally 450 MHz band (NMT 450), but later when more capacity was needed, it was also adopted for 900 MHz band (NMT 900).
1G (Analog) AMPS (Advanced Mobile Phone System) is the analog cellular phone system used in North and South America. AMPS uses FDMA and operates at 800 MHz band. AMPS was introduced in the USA in 1983. TACS (Total Access Communication System) was developed in Britain using the 900 MHz band. TACS was based on the AMPS system and was adopted in other countries such as Hong Kong and Japan. ETACS (Extended Total Access Communication System) was developed in the UK and is available in Europe and Asia.
2G (Digital) Uses digital encoding and includes CDMA, TDMA and GSM. Text messages can be sent on 2G networks, but more bandwidth hungry applications require 2.5G. Circuit switched In the United States, GSM, TDMA, and CDMA are assigned two frequency ranges that include the frequency ranges assigned to analog cellular, 824 MHz to 849 MHz and 869 MHz to 894 MHz, and also the frequency ranges of 1850 to 1910 MHz and 1930 MHz to 1990 MHz.
2G (Digital) CDMA (Code Division Multiple Access) uses a spread spectrum technique to scatter a radio signal across a wide range of frequencies. IDEN , (Integrated Digital Enhanced Network) is a wireless technology from Motorola combining the capabilities of a digital cellular telephone network. IDEN operates in the 800 MHz, 900MHz, and 1.5 GHz bands and is based on time division multiple access (TDMA) and GSM architecture.
2G (Digital) GSM (Global System for Mobile Communications) is the digital transmission technique widely adopted in Europe and supported in North America. GSM uses 900 MHz and 1800 MHz in Europe. In North America, GSM uses the 1900 MHz band.
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- Computer Science, Universal Mobile Telecommunications System, TDMA