| 摘要 |
In a network overlay wireless location solution for a GSM or UMTS communications network, spectrum utilization can be made far more efficient by synchronizing the BTSs, which can require distributing a timing signal to all BTSs, or installing a satellite-based timing unit in each site. The present invention provides an architecture in which Location Measurement Units (LMUs) are installed at some or all of the BTS sites for the purpose of locating wireless devices. The LMUs are used to measure the timing of various uplink and/or downlink signals in the cellular network in support of various location techniques. These LMUs may include a GPS-based timing reference module, which may be used to synchronize the time bases of all LMUs. To reduce the overall cost of BTS synchronization, the LMU distributes timing signals, including a periodic electrical pulse as well as time description information, on a serial or other interface, which is available for other nodes to use for synchronization. The format of the electrical pulse and time description information is modified through hardware and software to adapt to the various formats required by various BTS types. For example, the BTSs with co-located LMUs can receive a synchronization signal with little or no hardware cost. The External Interface Unit (EIU) described herein may be used to adapt to various BTS hardware formats. For BTS sites not equipped with an LMU, a Timing Measurement Unit (TMU) can be used. The TMU has the single function of providing BTS time signals in the same formats as provided by the LMUs. The time signals provided by the TMUs are synchronous to the signals provided by the LMUs. This timing-only TMU has a lower cost than the LMU because it does not support the uplink or downlink signal measurement functions. This approach allows a cellular operator to synchronize BTSs at a relatively low cost.
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