World wide used Cellular frequencies

All cellular 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 Blue tooth 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 Europe, the first widespread 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 the problem when they could not provide service to more and more customers. They had to develop their existing networks and eventually to introduce new standards, often based on other frequencies. The GSM standard, which appeared in Europe to replace NMT-450 and other standards, initially used the 900 MHz band. As demand grew, carriers acquired licenses in the 1800 MHz band. 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, most operators with GSM replaced IS-136 on these frequencies. 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 frequencies 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. 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.