In an overlay, U-TDOA-based, Wireless Location System, LMUs typically co-located with BTSs, are used to collect radio signaling both in the forward and reverse channels. Techniques are used to compensate for sparse LMU deployments where sections of the U-TDOA service area are uplink demodulation or downlink...http://www.google.fr/patents/US8041367?utm_source=gb-gplus-shareBrevet US8041367 - Sparsed U-TDOA wireless location networks
