====== Understanding UMTS, HSPA, WCDMA and GSM relationships ======


[[wp>UMTS]] (Universal Mobile Telecommunications System) is a technology that builds upon [[wp>GSM]] (Global System for Mobile communications). The same infrastructure used for GSM (the core network that includes routing, authentication, switching etc..) can be used for UMTS. In UMTS terminology it is  called UTRAN (UMTS Terrestrial Radio Access Network). UMTS adds performance over GSM by exploiting a wider radio band which provides high speed data channels. The radio technology used in UMTS is called [[wp>WCDMA]] (Wideband Code Division Multiple Access).


WCDMA is a radio interface, it plays the role of physical and data link layer in the OSI model (The equivalent of 802.11a/b/g, Ethernet, ...). It provides better performance compared to the GSM's original air interface called [[wp>Time_division_multiple_access|TDMA]] (Time Division Multiple Access) by specifying a modulation technique that exploits better the bandwidth (spectrum) of a device's transmission frequency. 


[[wp>HSUPA]] (High Speed Uplink Packet Access) and [[wp>HSDPA]] (High Speed Downlink Pacet Access) are two technologies that upgrade the original UMTS specification to add further performance enhancements. The combination is called HSPA (High Speed Packet Access) specifies data packet encapsulation and transport in UMTS.

===== Articles on wireless networks =====
 
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