Wireless Technologies
Digital wireless and cellular

Digital wireless and cellular date back to the 1940s when commercial mobile telephony began. The wireless revolution began after low cost microprocessors and digital switching became available, and the regulatory climate changed to allow less control of radio transmission equipment .

Cellular Radio
Cellular radio provides mobile telephone service by employing a network of cell sites distributed over a wide area. A cell site contains a radio transceiver and a base station controller. The base station manages, transmits, and receives traffic from the mobile radios in its geographical area. A cell site also has a tower and antennas, as well as a link to a distant switch, which is called a mobile telecommunications switching office (MTSO). The MTSO connects calls from land based telephones to wireless customers, switches calls between cells as mobiles travel across cell boundaries, and authenticates wireless customers before they make calls.

Cellular networks use a principle called frequency reuse to greatly increase the number of customers served. Frequency reuse is shown in Figure . Low powered mobile radios and the radio equipment at each cell site permit the same radio frequencies to be reused in different, noncontiguous cells, thus multiplying calling capacity without creating interference. This spectrum-efficient method sharply contrasts with earlier mobile systems that used a high-powered, centrally located transmitter to communicate with high-powered car mounted mobiles on a small number of frequencies. Channels were used and could not be re-used over a wide area.

Complex signaling routines handle call placements, call requests, and call transfers from one cell to another. These routines are referred to as handovers and roaming, and occur when a user moves from one carrier area to another carrier area. Different cellular radio systems use frequency division, multiple access (FDMA) analog, time division multiple access (TDMA), and spread spectrum code division multiple access (CDMA) techniques.

WLAN design is similar to that of cellular technologies. Instead of having one large, centralized, high-powered access point or bridge, WLANs favor the cellular model of using multiple low-powered base stations to maximize coverage, redundancy, and bandwidth capabilities.

Third Generation (3G)
Wireless 3G systems provide access to a wide range of telecommunication services supported by the fixed telecommunication networks, and to other services that are specific to mobile users. A range of wireless terminal types is encompassed, linking users to terrestrial or satellite-based networks. The terminals may be designed for mobile or fixed use.

3G systems have several key design features:

  • A high degree of commonality of design worldwide
  • Compatibility of services worldwide
  • Use of small pocket terminals with worldwide roaming capability
  • Access to the Internet and other multimedia applications
  • A wide range of services and terminals

According to the International Telecommunication Union (ITU) International Mobile Telecommunications 2000 Initiative (IMT-2000), 3G system services were scheduled to be initiated around the year 2000, depending on market considerations. It was later predicted that 3G services would be offered in 2001. However, 3G services did not begin to appear until 2002 and most industry observers say that these services are not true 3G services because they do not achieve 3G data rates.

Figure describes some of the key service attributes and capabilities expected of 3G systems.


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