A high performance position tracker for embedded paging, cellular telephone, and law enforcement applications

A highly compact and secure municipal area personnel tracking device is described. Position updates to a nominal accuracy of 20 meters for up to 1000 active users are required. Coverage over paging and cellular phone service areas, including most interior office space, is provided. The system is protected from unauthorized position monitoring and from jamming. Dependent tracking and independent tracking are considered. The selected tracking system uses a user beacon operating in the 900 MHz range, the signal emitted by each user consisting of 0.1-s bursts sent every 100 s. A time-bandwidth of 100000 is utilized to overcome high link attenuations and interference. To meet spoof and position-denial requirements, one-time bursts are used in each time slot. A custom all-digital signal correlation system was developed to meet the high processing gain and programmability requirements of master and remote monitor sites. Acquisition times are reduced by transmit time and time interval synchronization obtained over the existing paging or cellular-phone receive link