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2008-07-29T04:17:00.000-07:00

Cellular frequencies

From Wikipedia, the free encyclopedia

All cellular phone networks worldwide utilize a portion of the radio frequency spectrum designated as Ultra High Frequency, or "UHF", for the transmission and reception of their signals. The UHF band is also shared with Television, Wi-Fi and Bluetooth transmission. The cellular frequencies are the sets of frequency ranges within the UHF band that have been allocated for cellular phone use.

Due to historical reasons, radio frequencies used for cellular networks differ in the Americas, Europe, and Asia. The first commercial standard for mobile connection in the United States was AMPS, which was in the 800 MHz frequency band. In nordic countries of Europe, the first wide-spread automatic mobile network was based on the NMT-450 standard, which was in the 450 MHz band. As mobile phones became more popular and affordable, mobile providers encountered a problem because they couldn't provide service to the increasing number of customers. They had to develop their existing networks and eventually introduce new standards, often based on other frequencies. Some european countries (and Japan) adopted TACS operating in 900 Mhz. The GSM standard, which appeared in Europe to replace NMT-450 and other standards, initially used the 900 MHz band too. As demand grew, carriers acquired licenses in the 1800 MHz band. (Generally speaking, lower frequencies allow carriers to provide coverage for a larger area, while higher frequencies allow carriers to provide service to more customers in a given area.)

In the U.S., the analog AMPS standard that used the Cellular band (800 MHz) was replaced by a number of digital systems. Initially, systems based upon the AMPS mobile phone model were popular, including IS-95 (often known as "CDMA", the air interface technology it uses) and IS-136 (often known as D-AMPS, Digital AMPS, or "TDMA", the air interface technology it uses.) Eventually, IS-136 on these frequencies was replaced by most operators with GSM. GSM had already been running for some time on US PCS (1900 MHz) frequencies.

And, some NMT-450 analog networks have been replaced with digital networks utilizing the same frequency. In Russia and some other countries, local carriers received licenses for 450 MHz frequency to provide CDMA mobile coverage.

Many GSM phones support three bands (900/1800/1900 MHz or 850/1800/1900 MHz) or four bands (850/900/1800/1900 MHz), and are usually referred to as tri band and quad band phones, or world phones; with such a phone one can travel internationally and use the same handset. This portability is not as extensive with IS-95 phones, however, as IS-95 networks do not exist in most of Europe.

Mobile networks based on different standards may use the same frequency range; for example, AMPS, D-AMPS, N-AMPS and IS-95 all use the 800 MHz frequency band. Moreover, one can find both AMPS and IS-95 networks in use on the same frequency in the same area that do not interfere with each other. This is achieved by the use of different channels to carry data. The actual frequency used by a particular phone can vary from place to place, depending on the settings of the carrier's base station.

2008-07-29T04:10:00.000-07:00

Cellular network

From Wikipedia, the free encyclopedia

A cellular network is a radio network made up of a number of radio cells (or just cells) each served by a fixed transmitter, known as a cell site or base station. These cells are used to cover different areas in order to provide radio coverage over a wider area than the area of one cell. Cellular networks are inherently asymmetric with a set of fixed main transceivers each serving a cell and a set of distributed (generally, but not always, mobile) transceivers which provide services to the network's users.

Cellular networks offer a number of advantages over alternative solutions:

increased capacity
reduced power usage
better coverage

A good (and simple) example of a cellular system is an old taxi driver's radio system where the taxi company will have several transmitters based around a city each operated by an individual operator.

2008-07-29T03:27:00.000-07:00

Mobile phone
From Wikipedia, the free encyclopedia

Several examples of non-flip mobile phones.

The mobile phone (also called a wireless phone or cellular phone) is a short-range, portable electronic device used for mobile voice or data communication over a network of specialized base stations known as cell sites. In addition to the standard voice function of a telephone, current mobile phones may support many additional services, and accessories, such as SMS for text messaging, email, packet switching for access to the Internet, gaming, bluetooth, infrared, camera with video recorder and MMS for sending and receiving photos and video. Most current mobile phones connect to a cellular network of base stations (cell sites), which is in turn interconnected to the public switched telephone network (PSTN) (the exception is satellite phones).

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Datacell Pitaloka

Cellular frequencies

From Wikipedia, the free encyclopedia

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Cellular network

From Wikipedia, the free encyclopedia

Contents

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