Estimation of Bias Location Error due to Absence of the LOS-Signal in a UMTS-System

Current location methods for cellular communication systems TOA and E-OTD exploit time delays and time differences of various base station signals measured in a mobile phone to determine its location. These methods assume line-of-sight (LOS) connections to all utilized base stations. Since mobile radio channels are mainly characterized by scattered propagation paths and non-line-of-sight (NLOS) propagation, bias errors occur when measured time delays and time differences are utilized in position calculation algorithms. In this paper, the distribution of the time error due to NLOS propagation is estimated based on the channel model proposed in [1]. In combination with actual channel measurements in [2] the NLOS time error and its probability distribution function is estimated. With this information being determined for each received signal, position calculation algorithms can utilize the reliability information to enhance positioning accuracy. [1] L. J. Greenstein, V. Erceg, Y. S. Yeh, M. V. Clark, {grqq}A new path-gain/delay-spread propagation model for digital cellular channels'', IEEE Transactions on Vehicular Technology, Vol. 46, No. 2, May 1997 [2] H. Asplund, {grqq}Wideband Channel Measurements in Central Stockholm'', T1P1.5/98-242r1