Mobile positioning for third generation WCDMA systems
Mats Cedervall · 2002
For wideband mobile CDMA systems the paper describes three positioning methods and their performance is examined by means of computer simulations. These methods are the ones that seem to be of particular interest because of their performance. Briefly, the first method is an uplink (UL) method in which the mobile is ordered to switch its operation mode into transmitting a known training sequence at an increased power. This method is referred to as the known-UL method. The second method is also a UL method, but with unknown data transmitted by the mobile station (MS). The method can also use optional short codes (SC). By doing this the receiver time-of-arrival (TOA) estimation algorithms are simplified and the prior knowledge of the timing can be relaxed. This method is referred to as unknown-UL. The third method is a downlink method in which the base stations (BSs) cease the transmission of all downlink transmission for short time-periods, in order to improve the detection for the MSs. The method is called idle slot DL (IS-DL). Without using idle periods, the MS suffers from severe near-far problems if it is close to a BS. An advantage with the IS-DL method is that it is possible to place a test-MS in each BS in order to obtain relative timing. By doing this there is no need for e.g. GPS receivers in the BSs. We mainly focus on radio layer problems. It is assumed that there is functionality for the higher level signaling that is required.