Position enhanced communication system including system for embedding CDMA navigation beacons under the communications signals of a wireless communication system
US5604765A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 23, 1994 |
| Grant date | Feb 18, 1997 |
| Priority date | — |
| Expiry date | Dec 23, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L5/1469
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A cellular telephone system having three or more cell sites with each cell site having a source of cellular communication signals and an RF transmitter and antenna for broadcasting the cellular communication signals. A direct sequence spread spectrum waveform carrying navigation signals is embedded in the cellular communication signals, including controlling the signal strength of the navigation signals so that the combined energy of the navigation signals from all cell sites at any location is at least a predetermined energy level below the energy level of the cellular communication signals. Each cell site includes timing for timing the operation of a GPS receiver. An RF signpost system comprising a plurality of low powered RF broadcast stations, one each at a plurality of scattered geographic locations, each low powered RF broadcast station broadcasting a direct sequence spread spectrum digital RF waveform and a modulator to modulate the digital RF waveform with location information identifying the geographic locations, respectively.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.