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We investigate the problems encountered in mobile position locating (PL) in cellular networks. The two main problems are the inaccuracy of the estimated position and the hearability of the PL terminal, i.e., the ability to receive sufficient signals from at least 3 base stations (BS) to estimate its position. Our work is based on the downlink time difference of arrival (TDOA) positioning technique proposed for the LoCating Services (LCS) in GSM and wideband CDMA. We also study the effect of the non-line-of-sight (NLOS) link between the BS and mobile terminal (MT) on the accuracy of the estimated position. The idle period downlink (IPDL) scheme, proposed for the WCDMA network to mitigate the inaccuracy and hearability problems caused by interferences from other 'active' users or BS, is also addressed.