Reduced complexity signature based mobile terminal location relying on the knowledge of directional channel impulse responses

In mobile radio scenarios with multipath propagation the impulse responses of the channels between a mobile terminal (MT) and the base stations (BS) are in general unique signatures of the position of the MT. This fact can be exploited for MT location by first determining the channel impulse responses (CIR) off-line for sufficiently densely spaced reference points and storing these data in a data base, and then matching on-line measured CIRs to the data base entries. Unfortunately, this rationale would require a prohibitively large data base, because the CIRs may be totally different even for MT positions separated from each other by less than one wavelength λ. In the paper a CIR-based location scheme is proposed which can do with a data base of substantially reduced size. This reduction resorts to the observation that the CIRs are made up by individual wave fronts which remain unaltered over geographical areas with dimensions much larger than λ.