Universal Mobile Telecommunications System
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picocell
A picocell is a small cellular basestation typically covering a small area, such as in-building (offices, shopping malls, train stations, etc.), or more recently in-aircraft. In cellular networks, picocells are typically used to extend coverage to indoor areas where outdoor signals do not reach well, or to add network capacity in areas with very dense phone usage, such as train stations. Picocells provide coverage and capacity in areas difficult or expensive to reach using the more traditional Macrocell approach.


macrocell

is a cell in a mobile phone network that provides radio coverage served by a high power cellular base station (tower). Generally, macrocells provide coverage larger than microcell. The antennas for macrocells are mounted on ground-based masts, rooftops and other existing structures, at a height that provides a clear view over the surrounding buildings and terrain. Macrocell base stations have power outputs of typically tens of watts



A microcell

is a cell in a mobile phone network served by a low power cellular base station (tower), covering a limited area such as a mall, a hotel, or a transportation hub. A microcell is usually larger than a picocell, though the distinction is not always clear. A microcell uses power control to limit the radius of its coverage area.



Universal Mobile Telecommunications System
Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular technology for networks based on the GSMstandard. Developed by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the International Telecommunications UnionIMT-2000 standard set and compares with the cdma2000 standard set for networks based on the competing cdmaOne technology. UMTS employs wideband code division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators. UMTS specifies a complete network system,


Subscriber Identity Module (SIM)
Main article: Subscriber Identity Module
One of the key features of GSM is the Subscriber Identity Module, commonly known as a SIM card. The SIM is a detachable smart card containing the user's subscription information and phone book. This allows the user to retain his or her information after switching handsets. Alternatively, the user can also change operators while retaining the handset simply by changing the SIM.