Exploiting Position Information for Synchronization in Coordinated Multipoint Transmission

Abstract

Cellular communications systems suffer from interference in particular at cell edge regions. This is also the case for downlink synchronization signals. Such synchronization signals are base station specific and uperimpose at a mobile terminal with different delays and amplitudes. This causes inter cellular interference depending on the cross correlation properties of the particular synchronization signals. Assuming knowledge about the positions of the serving and interfering base stations and having available a position estimate of the mobile terminal, there is a-priori information about the different signal propagation delays at the mobile terminal's position. Using this information, synchronization signals received from adjacent base stations can be timely related. For this reason, former interference can at least partly be turned into useful signal and exploited for improving synchronization performance especially at the critical cell edge regions. Within this paper we evaluate the benefit of position information for a mobile terminal in order to improve mobile terminal synchronization performance. The analysis is based on calculating the Cramer-Rao lower for this particular problem. In particular, we will derive additional Fisher information about OFDM symbol timing from position information about the mobile terminal.