Signal detector and method employing a coherent accumulation system to correlate non-uniform and disjoint sample segments

• US 6,850,557 B1
• Filed: 04/18/2000
• Issued: 02/01/2005
• Est. Priority Date: 04/18/2000
• Status: Expired due to Term

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Gronemeyer, Steven A.
• Primary Examiner(s): Liu, Shuwang
• Assistant Examiner(s): PUENTE, EVA YI ZHENG
• Application Number:
  US09/551,047
• Time in Patent Office: 1,750 Days
• Field of Search: 375/150, 375/219, 342/357.1, 342/357.09, 342/357.12
• US Class Current: 375/150
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 2027/0034 using hypothesis testing

Abstract

A signal detector employs a coherent accumulation system that coherently combines the correlation results derived from segments of samples of a received signal. The segments may have non-uniform lengths and may have been obtained over different and non-overlapping time periods. The segments are obtained during sampling windows of arbitrary length and at arbitrary times, and the results of processing the segments are successively combined in a coherent manner (separate magnitude and phase accumulation) until a threshold signal-to-noise ratio (SNR) has been achieved. Coherent integration is enabled by introducing a carrier phase offset as well as a code phase offset, so that different segments are aligned in carrier phase as well as code phase. Although not limited to this application, in one implementation example, the signal detector is used in connection with and as part of a global positioning system (GPS) receiver.

Claims

1. A system comprising:

a receiver configured to receive a first segment of a signal and a second segment of the signal, the first and second segments acquired during separate periods of time, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

a correlator coupled to the receiver, the correlator configured to derive first correlation data representative of a first correlation between the first segment and a hypothesis, the correlator configured to impose a carrier offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment, the correlator configured to derive second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

a combiner coupled to the correlator, the combiner configured to coherently combine the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

2. The system of claim 1, wherein the combiner is further configured to determine a code phase offset between the first and second correlation data, to adjust a selected one of the first and second correlation data responsive to the code phase offset, and to combine the adjusted data with the other of the first and second correlation data.

3. The system of claim 1, wherein the receiver is an RF receiver.

4. The system of claim 1, wherein the signal of interest is a carrier signal modulated with a repeating PN code.

5. The system of claim 1, wherein the correlator is a matched filter.

6. The system of claim 1, wherein the correlator is a processor.

7. The system of claim 1, wherein the combiner is a processor.

8. The system of claim 1, wherein the combiner is configured to successively combine the correlation data for successive segments until the signal of interest or a parameter of interest can be accurately and reliably detected.

9. The system of claim 7, wherein the parameter of the signal of interest is the carrier signal.

10. The system of claim 7, wherein the parameter of the signal of interest is the presence of the signal.

14. The system of claim 1 wherein the signal of interest is a carrier signal modulated with a repeating PN code.

11. A system comprising:

first means for acquiring a first segment of a signal and a second segment of the signal during separate periods of time, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

second means for deriving first correlation data representative of a first correlation between the first segment and a hypothesis, for imposing a carrier offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment, for deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

third means for coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

12. The system of claim 11, wherein the third means further performs the function of determining a code phase offset between the first and second correlation data, to adjust a selected one of the first and second correlation data responsive to the code phase offset, and to combine the adjusted data with the other of the first and second correlation data.

13. The system of claim 11, wherein the first means is an RF receiver.

15. The system of claim 11, wherein the second means is a matched filter.

16. The system of claim 11, wherein the second means is a processor.

17. The system of claim 11, wherein the third means is a processor.

18. The system of claim 11, wherein the third means performs the function of successively combine the correlation data for successive segments until the signal of interest or a parameter of interest can be accurately and reliably detected.

19. The system of claim 11, wherein the parameter of the signal of interest is the carrier signal code phase of the signal.

20. The system of claim 11, wherein the parameter of the signal of interest is the presence of the signal.

21. A computer read able medium having a program, the program comprising:

logic to acquire a first segment of a signal and a second segment of the signal that have been sampled during separate time periods, the first and second segments having nonuniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

logic to derive first correlation data representative of a first correlation between a first segment of a signal and a hypothesis, for imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment, for deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

logic to coherently combine the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

22. A system comprising:

a receiver for receiving a first segment of a signal and a second segment of the signal, the signal representative of a plurality of signals of interest, each signal of interest representative of a repeating PN code modulated onto a carrier signal, the first and second segments having non-uniform lengths, and the first and second segments representing separate and distinct periods of time;

a correlator coupled to the receiver for deriving first correlation data representative of the correlation between the first segment and a combined PN code and code phase hypothesis, the correlator configured to impose a carrier phase offset upon the second segment so that a carier phase of the second segment corresponds to that of the first segment, the correlator configured to derive second correlation data representative of a second correlation between the phase shifted second segment and the combined code and code phase hypothesis; and

a combiner coupled to the correlator for determining a code phase difference between portions of the first and second correlation data corresponding to the PN code hypothesis, for adjusting a selected one of the portions of the first and second correlation data responsive to the code phase difference, and combining the adjusted data with the other portion to obtain cumulative correlation data useful for detecting a signal of interest or a parameter of a signal of interest.

23. A method comprising the steps of:

acquiring a first segment of a signal and a second segment of the signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

24. The method of claim 23, further comprising the steps of:

determining a code phase offset between the first and second correlation data;

adjusting a selected one of the first and second correlation data responsive to the code phase offset; and

combining the adjusted data with the other of the first and second correlation data.

25. The system of claim 23, wherein the acquiring step is performed with an RF receiver.

26. The system of claim 23, wherein the signal of interest is a carrier signal modulated with a repeating PN code.

27. The system of claim 23, wherein the deriving steps are performed using a matched filter.

28. The system of claim 23, wherein the deriving steps are performed using a processor.

29. The system of claim 23, wherein the combining step is performed using a processor.

30. The system of claim 23, wherein the parameter of the signal of interest is the carrier signal code phase of the signal.

31. The system of claim 23, wherein the parameter of the signal of interest is the presence of the signal.

32. A computer readable medium having a program comprising:

logic configured to acquire a first segment of a signal and a second segment of the signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

logic configured to derive first correlation data representative of a first correlation between a first segment and a hypothesis;

logic configured to impose a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

logic configured to derive a second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

logic configured to coherently combine the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

33. The computer readable medium of claim 32, further comprising:

logic configured to determine a code phase offset between the first and second correlation data;

logic configured to adjust a selected one of the first and second correlation data responsive to the code phase offset; and

logic configured to combine the adjusted data with the other of the first and second correlation data.

34. The computer readable medium of claim 32, wherein the logic configured to acquire a first segment of a signal and a second segment of the signal is implemented in an RF receiver.

35. The computer readable medium of claim 32, wherein the signal of interest is a carrier signal modulated with a repeating PN code.

36. The system of claim 32, wherein the logic configured to derive second correlation data is implemented in a matched filter.

37. The system of claim 32, wherein the parameter of the signal of interest is the carrier signal code phase of the signal.

38. The system of claim 32, wherein the parameter of the signal of interest is the presence of the signal.

39. A GPS receiver, comprising:

a first GPS antenna coupled to a digital memory, the digital memory storing first digitized signals obtained through the first GPS antenna;

a second GPS antenna coupled to a digital memory, the digital memory storing first digitized signals obtained through the second GPS antenna;

a digital processor coupled to the digital memory, the digital processor processing the first digitized signals after being stored in the digital memory to provide first position information and processing the second digitized signals after being stored in the digital memory to provide second position information;

a receiver configured to receive a first segment of a signal and a second segment of a signal, the first and second segments acquired during separate periods of time, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

a correlator coupled to the receiver, the correlator configured to derive first correlation data representative of a first correlation between the first segment and a hypothesis, the correlator configured to impose a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment, the correlator configured to derive second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

a combiner coupled to the correlator configured to coherently combine the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

40. A method of operating a GPS receiver, the method comprising:

receiving first GPS signals through a first GPS antenna;

digitizing the first GPS signals to provide first digitized signals and storing the first digitized signals in a first digital memory;

receiving second GPS signals through a second GPS antenna;

digitizing the second GPS signals to provide second digitized signals and storing the second digitized signals in one of the first digital memory and a second digital memory;

processing in a digital processor the stored first digitized signals to provide a first position information and processing the stored second digitized signals to provide a second position information;

selecting one of the first position information and the second position information to provide a selected position information;

when performing the processing step, performing the following steps upon one or both of the first and second GPS signals;

acquiring a first segment of a signal and a second segment of the signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

41. A method for determining a position of a mobile global positioning system receiver, the mobile global positioning system receiver receiving global positioning system signals from at least one of a plurality of global positioning system (GPS) satellites, the method comprising:

receiving a cellular communication signal in a mobile communication receiver coupled to the mobile global positioning system receiver, the cellular communication signal having a time indicator which represents a time event;

associating the time indicator with data representing a time of arrival of a GPS satellite signal at the mobile global positioning system receiver;

determining position information of the mobile global positioning system receiver, wherein the data representing the time of arrival of the GPS satellite signal and the time indicator are used to determine the position information of the mobile global positioning system receiver and wherein the cellular con nun cation signal supports 2-way communications; and

when performing the determining step;

acquiring a first segment of a signal and a second segment of the signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

42. A method of operating a global positioning system (GPS) receiver, comprising:

sensing whether GPS signals are capable of being received from GPS satellites and providing an activation signal when the GPS signals are capable of being received;

maintaining the GPS receiver in a low power state;

activating the GPS receiver form the lower power state upon detecting the activation signal;

acquiring a first segment of a signal and a second segment of a GPS signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

43. A method for using a dual mode GPS receiver, the method comprising the steps of:

activating the GPS receiver in a first mode of operation, including,

receiving GPS signals from, in view satellites;

downconverting and demodulating the GPS signals to extract Doppler information regarding in view satellites and to compute pseudorange information;

storing the Doppler information;

detecting when the GPS receiver is experiencing blockage conditions and activating a second mode of operation in response thereto, the second mode including, digitizing the GPS signals at a predetermined rate to produce sampled GPS signals;

acquiring a first segment of a signal and a second segment of a GPS signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segmnent and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

44. In a method for determining the position of a remote unit a process comprising:

receiving, at the remote unit from a transmission cell in a cellular communication system, a Doppler information of a satellite in view of the remote unit;

computing, in the remote unit, position information for the satellite by using the Doppler information without receiving and without using satellite ephemeris information; and

when computing the position information, performing the following steps;

acquiring a first segment of a signal and a second segment of the signal during separate time periods, the first and second segments having non-uniform length, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segnent so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

45. A method of using a base station for providing a communications link to a mobile GPS unit, the method comprising:

determining Doppler information of a satellite in view of the mobile GPS unit, wherein the Doppler information is used by the mobile GPS unit to determine a position information for the satellite;

transmitting from a transmission cell in a cellular communication system the Doppler information of the satellite in view to the mobile GPS unit wherein the mobile GPS unit determines the position information without receiving and without using satellite ephemeris information; and

when performing the determining step, performing the following steps;

acquiring a first segment of a signal and a second segment of the signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

46. A method of determining the location of a remote object, comprising the steps of:

transporting a positioning sensor to a remote object;

repositioning the positioning sensor to a fix position such that the positioning sensor is capable of receiving positioning signals, the fix position being in a known position relative to the position of the remote sensor;

storing a predetermined amount of data in the positioning sensor while the positioning sensor is located at the fix position, the data comprising the positioning signals;

processing the data to determine the location of the fix position;

computing the location of the remote object using the location of the fix position; and

when performing the processing step, performing the following steps;

acquiring a first segment of a signal and a second segment of a signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

47. A method of tracking a remote object comprising the steps of:

fitting a remote object with a positioning sensor configured to receive and store positioning information when the remote object is in a fix position;

positioning the remote object in a fix position such that the positioning sensor is capable of detecting an activation signal;

receiving and storing a predetermined amount of data in the positioning sensor, the data comprising positioning information;

processing the data to determine the location of the fix position; and

when processing the data, performing the following steps;

acquiring a first segment of a signal and a second segment of a signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

48. A computer readable medium containing a computer program having executable code for a GPS receiver, the computer program comprising:

first instruction for receiving GPS signals from in view satellites, the GPS signals comprising pseudorandom (RN) codes;

second instructions for digitizing the GPS signals at a predetermined rate to produce sampled GPS signals;

third instructions for storing the sampled GPS signals in a memory; and

fourth instructions for processing the sampled GPS signals by performing a plurality of convolutions on the sampled GPS signals, the processing comprising performing the plurality of convolutions on a corresponding plurality of blocks of the sampled GPS signals to provide a plurality of corresponding results of each convolution and summing a plurality of mathematical representations of the plurality of corresponding results to obtain a first position information; and

wherein the further instructions are designed to;

acquire a first segment of a signal and a second segment of a signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

derive first correlation data representative of a first correlation between the first segment and a hypothesis;

impose a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

derive second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combine the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

49. A computer readable medium containing an executable computer program for use in a digital processing system, the executable computer program when executed in the digital processing system causing the digital processing system to perform the steps of:

performing a plurality of convolutions on a corresponding plurality of blocks of sampled GPS signals to provide a plurality of corresponding results of each convolution; and

summing a plurality of mathematical representations of the plurality of corresponding results to obtain a first position information; and

when performing the plurality of convolutions step, performing at least the following steps;

acquiring a first segment of a signal and a second segment of the signal during separate time periods the first and second segments hair non-uniform lenths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a cater phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

50. A method of calibrating a local oscillator in a mobile GPS receiver, the method comprising:

receiving a precision carrier frequency signal from a source providing the precision carrier frequency signal;

automatically locking to the precision carrier frequency signal and providing a reference signal;

calibrating the local oscillator with the reference signal, the local oscillator being used to acquire GPS signals;

acquiring a first segment of a signal and a second segment of a GPS signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

51. A method of using a base station to calibrate a local oscillator in a mobile GPS receiver, the method comprising:

producing a first reference signal having a precision frequency;

modulating the first reference signal with a data signal to provide a precision carrier frequency signal;

transmitting the precision carrier frequency signal to the mobile GPS receiver, the precision carrier frequency signal being used to calibrate a local oscillator in the mobile GPS receiver, the local oscillator being used to acquire GPS signals;

acquiring a first segment of a signal and a second segment of a GPS signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

52. A method of deriving a local oscillator signal in a mobile GPS receiver, the method comprising:

receiving a precision carrier frequency signal from a source providing the precision carrier frequency signal;

automatically locking to the precision carrier frequency signal and providing a reference signal;

using the reference signal to provide a local oscillator to acquire GPS signals;

acquiring a first segment of a signal and a second segment of a GPS signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

53. A method of processing position information, the method comprising:

receiving GPS signals from at least one GPS satellite;

transmitting cell base communication signals between a communication system coupled to the GPS receiver and a first cell based transceiver which is remotely positioned relative to the GPS receiver wherein the cell based communication signals are Wireless;

determining a first time measurement which represents a time of travel of a message in the cell based communication signals in a cell based communication system which comprises the first cell based transceiver and the communication system;

determining a second time measurement which represents a time of travel of the GPS signals;

determining a position of the GPS receiver from at least the first time measurement and the second time measurement wherein the cell based communication signals are capable of communicating data messages in a two-way direction between the first cell based transceiver and the communication system;

performing the following steps during at least one of the determining steps;

acquiring a first segment of a signal and a second segment of a GPS signal during separate time periods the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

54. A method of processing position information in a digital processing system, the method comprising:

determining a first time measurement which represents a time of travel of a message in cell based communication signals in a cell based communication system which comprises a first cell based transceiver which communicates with the digital processing system and a communication system which communicates in a wireless manner with the first cell based transceiver,

determining a position of a GPS receiver from at least the first time measurement and a second time measurement which represents a time of travel of GPS Signals received at the GPS receiver which is integrated with the communication system and is remotely located relative to the first cell based transceiver and the digital processing system, wherein the cell based communication signals are capable of communicating messages from the communication system to the first cell based transceiver; and

performing the following steps when determining the position;

acquiring a first segment of a signal and a second segment of a signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising a signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segment so that a carrier phase of the second segment corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.

55. A method of controlling a communication link and processing data representative of GPS signals from at least one satellite in a GPS receiver, the method comprising:

processing the data representative of GPS signals from at least one satellite in a processing unit, including performing a correlation function to determine a pseudorange based on the data representative of the GPS signals;

controlling communication signals through the communication link by using the processing unit to perform the controlling and wherein the processing unit performs demodulation of communications signal sent to the GPS receiver; and

when performing the processing step, performing at least the following steps;

acquiring a first segment of a signal and a second segment of a GPS signal during separate time periods, the first and second segments having non-uniform lengths, the signal comprising it signal of interest perturbed by noise or pseudo-noise;

deriving first correlation data representative of a first correlation between the first segment and a hypothesis;

imposing a carrier phase offset upon the second segmnent so that a carrier phase of the second segmnent corresponds to that of the first segment;

deriving second correlation data representative of a second correlation between the phase shifted second segment and the hypothesis; and

coherently combining the first and second correlation data to obtain cumulative correlation data useful for detecting the signal of interest or a parameter of the signal of interest.