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Cellular Radio


Published on Dec 12, 2015

Abstract

Cellular mobile radio systems aim to provide high-mobility, wide-ranging, two-way wireless voice communications. These systems accomplish their task by integrating wireless access with large-scale networks, capable of managing mobile users. Cellular radio technology generally uses transmitter power at a level around 100 times that used by a cordless telephone (approximately 2 W for cellular).

Standards

Cellular radio has evolved into digital radio technologies, using the systems standards of GSM (at 900 and 1800 MHz) in Europe, PDC in Japan, and IS-136A and IS-95A in the United States. Third-generation systems, such as wideband code division multiple access (WCDMA) and cdma2000, are currently under development.

Design Considerations

One of the most significant consideration in designing digital systems is the high cost of cell sites. This has motivated system designers to try to maximize the number of users per megahertz, and users per cell site. Another important consideration is maintaining adequate coverage in areas of varying terrain and population density. For example, in order to cover sparsely populated regions, system designers have retained the high-power transmission requirement to provide maximum range from antenna locations.

Communications engineers have also been developing very small coverage areas, or microcells. Microcells provide increased capacity in areas of high user density, as well as improved coverage of shadowed areas. Some microcell base stations are installed in places of high user concentrations,

The mobile radio is a two-way communication gadget that operates through radio frequencies. As such, the channel of information and messages in a mobile radio is variable. Used to be known as radiophone, the earlier versions of the mobile radio, were one-way communication systems used for broadcast.

Contemporary mobile radio systems can have as much as a hundred channels and may be controlled by microprocessors. These types require the use of software to encode channels and operate their integrated functions. The mobile radio, also known as a two-way radio system, allows the exchange of messages only with other mobile radios through push-to-talk (PTT) functions. A mobile radio also features wireless transceivers, making mobile radios portable. Mobile radio systems may be used for communications in aircraft, ships, automobiles, and other vehicles. The power supply on which mobile radios run depend on the type of vehicle these are mounted on.

A mobile radio system is composed of a transceiver and microphone with a push-to-talk key. It has an antenna that links to the transceiver. Since most types of mobile radio are used in moving vehicles, where the surrounding noise can be loud, some mobile radio types come with an external speaker. Other models have headsets and microphones with noise-reduction capabilities.

How does a mobile radio work?

Most mobile radios operate on a single band of frequency. The radio transceiver contains transmit and receive frequencies. Very high frequency (VHF) and ultra high frequency (UHF) allow a mobile radio to operate on maximum coverage. This means that its average operating range is from 150 to 470 MHz.

To transmit a message, the PTT key must be pressed during talk-time to allow the voice message to be dispatched by the sending party. During this period, the sending party cannot hear or receive any incoming messages from the mobile radio. Once the PTT button is released, the sender may hear the response of the receiving party.

Why do we need a mobile radio

The use of mobile radio in transportation, security, and general operations makes communication fast, efficient and safe. It allows control centers to monitor location of vehicles and dispatch announcements to several receivers simultaneously.

Additionally, the range of its area coverage is very high and is not dependent on a cellular network, which may fluctuate during emergency situations.

Different types of mobile radio are portable and capable of withstanding shock and severe weather conditions. Most countries impose certain requirements on the manufacture, sale and use of two-radio systems. This helps ensure that the communication gadget functions according to standards and that its use does not interfere with other communication systems.














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