V. N. Makovsky, I. V. Chebotar, V. V. Kuzmin, Yu. N. Gaichuk

Subsystems of mobile terminal position-finding in GSM and UMTS networks are examined in this article. Differences between GSM and UMTS network position-finding system architecture which are specified by more represented core network partitioning in UMTS networks as well as possibility in principle of various implementations of access networks have been reviewed. It has been detected that the fundamental difference of GSM network structure from UMTS network structure is the final assignment of SMLC (Serving Mobile Location Center) functions to RNC (Radio Network Controller) ? similarity of base station controller in GSM network. Moreover, GMLC (Gateway Mobile Location Center) is more functionally separated as an independent unit. It is physically separated from the rest of the basic network components. Gateway Mobile Location Centers of other mobile networks can address to a service nodes for the required information to determine a position. It has been discovered that the most unsophisticated methods of positioning (Cell ID, Cell ID - TA for GSM standard) use only information available in that network for a mobile terminal position-finding. But these methods have a rather poor accuracy of positioning therefore they can be implemented in restricted spheres. More exact methods require major modification of the network components, for example, installing of smart antennas at base stations, creating libraries of templates "radiostamps" for any base station, creating of reference nodes, etc. It appreciably raises the price of a system; makes it more sophisticated in operation, which in turn establish unacceptable conditions for practical implementation. We've got to face up to the fact that A-GPS should be recognized as the most accurate method of positioning. Mobile terminal is actively involved in position-finding during the implementation of this method while the main part of calculations is performed in the hardware of the communication network. To solve tasks of estimation of mobile subscriber spatial characteristics without total access to information within cellular-radio system the structural and statistical estimation method was suggested. The essence of this method is position determination of mobile station within only one cell based on a comparison of the distribution of changes in the transmitter power in the base station control channel with reference. This method allows obtaining information about the spatial position of the mobile subscribers even we have a short-time reception of the base station control channel.