System and method for the mitigation of cdma cross-corrlation artifacts and the improvement of signal-to-noise ratios in tdma location networks

• US 20070058591A1
• Filed: 08/03/2004
• Published: 03/15/2007
• Est. Priority Date: 08/04/2003
• Status: Active Grant

• Current Assignee: David Small, James Lamance
• Original Assignee: David Small, James Lamance
• Inventors: Small, David, Lamance, James
• Granted Patent: US 7,463,617 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04B 2001/70706 using a code tracking loop, e.g. a delay locked loop
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713

Abstract

A correlation system for Time Division Multiple Access (TDMA) positioning systems is disclosed, whereby a position receiver acquires, tracks, and demodulates a plurality of Code Division Multiple Access (CDMA) modulated positioning signals are pulsed in a Time Division Multiple Access (TDMA) scheme. A specialized correlation processor within the position receiver is configured to internally generate pseudo-random number (PRN) code signal replicas of Code Division Multiple Access (CDMA) positioning signals in synchronicity with their respectively received Time Division Multiple Access (TDMA) positioning signals. This correlation system provides the position receiver with range measurements free from the deleterious effects of Code Division Multiple Access (CDMA) cross-correlation artifacts and degraded signal-to-noise ratios, therefore allowing the computation of high accuracy position solutions.

Claims

1. A method for providing accurate positioning signals In a TDMA positioning system to a position receiver configured with at least one correlator, said positioning receiver mitigating cross-correlation artifacts and exhibiting high signal-to-noise ratios, the method comprising:

a) transmitting said positioning signals in a known TDMA sequence;

b) chronologically synchronizing said position receiver to said known TDMA sequence of said positioning signals;

c) configuring said at least one correlator to sequentially track said positioning signals in synchronicity with said known TDMA sequence.

2. The method of claim 1, wherein said configuring further includes said at least one pseudo-random number (PRN) code sequence generator replicating the pseudo-random number (PRN) code sequence of said positioning signals in synchronicity with said known TDMA sequence.

3. A method of sequentially receiving a plurality of TDMA positioning signals broadcast in a known TDMA sequence, the method comprising:

a) deploying a position receiver containing;

i) means to receive and interpret said TDMA positioning signals;

ii) at least one correlator communicatively coupled to said position receiver, each correlator configured with;

I. means for providing a master timing reference for said correlator;

II. means to analyse the relationship between the reception time of the TDMA positioning signals and said master timing reference, and subsequently determine the start and stop times of the correlator integration interval relative to said master timing reference;

III. means to sequentially generate the next PRN code of the known TDMA sequence responsive to said determined start and stop times;

b) receiving at least one TDMA positioning signal at said position receiver and determining said reception time of said TDMA signals;

c) communicating said determined reception time to said at least one correlator, thereby generating a PRN sequence in synchronicity with the reception of said TDMA positioning signals.