Method of despreading GPS spread spectrum signals

• US 6,525,689 B2
• Filed: 05/22/2001
• Issued: 02/25/2003
• Est. Priority Date: 05/31/2000
• Status: Expired due to Term

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Yule, Andrew T., Dooley, Saul R.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/862,291
• Publication Number:
  US 20020001339A1
• Time in Patent Office: 644 Days
• Field of Search: 342/357.1, 342/357.09, 342/357.12, 701/213
• US Class Current: 342/357.43
• CPC Class Codes: G01S 19/06 employing an initial estimate of the location of the receiver as aiding data or in generating aiding data
• CPC Class Codes: G01S 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker

Abstract

A method of despreading a GPS spread spectrum signal received at a mobile unit MSl with assistance from a base station BS1 includes (a) receiving and despreading GPS signals at the base station and deriving GPS signal information therefrom; (b) estimating the location of the mobile unit; (c) modifying the OPS signal information so as reflect the GPS signal characteristics as would be observed at the estimated location of the mobile unit; (d) transmitting the GPS signal information from the base station to the mobile unit; (e) generating replica signals containing PRN codes corresponding to those of the GPS signal using the modified GPS signal information; and (f) performing a correlation of the GPS signal and the replica signals in order to acquire the GPS signal.

Claims

1. A method of despreading a GPS spread spectrum signal received at a mobile unit with assistance from a base station comprising the steps of:

(a) receiving and despreading GPS signals at the base station and deriving GPS signal information therefrom;

(b) estimating the location of the mobile unit;

(c) modifying the GPS signal information so as reflect the GPS signal characteristics as would be observed at the estimated location of the mobile unit;

(d) transmitting the GPS signal information from the base station to the mobile unit;

(e) generating replica signals containing PRN codes corresponding to those of the GPS signal using the modified GPS signal information; and

(f) performing a correlation of the GPS signal and the replica signals in order to acquire the GPS signal.

2. A method according to claim 1 wherein step (c) is done before step (d).

3. A method according to claim 2 wherein the initial estimate of the location of the mobile unit is determined in the mobile unit and transmitted to the base station.

4. A method according to claim 1 wherein the GPS signal information comprises Doppler information.

5. A method according to claim 1 wherein the GPS signal information comprises code phase information.

6. The combination of a base station (BS1) and a mobile unit (MS1) for despreading a GPS spread spectrum signal received at a mobile unit with assistance from a base station by a method according to claim 1.

7. The combination of a base station and a mobile unit for despreading a GPS spread spectrum signal received at a mobile unit with assistance from a base station;

wherein the base station comprises a GPS receiver for receiving and despreading GPS signals at the base station and deriving GPS signal information therefrom, a processor arranged to modify the GPS signal information so as reflect the GPS signal characteristics as would be observed at an estimated location of the mobile unit; and

a transmitter for transmitting the modified GPS signal information from the base station to the mobile unit; and

wherein the mobile unit comprising a GPS receiver for receiving the GPS signal, a communications receiver for receiving GPS signal information from a base station; and

a processor arranged to generate replica signals containing PRN codes corresponding to those of the GPS signal using the modified GPS signal information and perform a correlation of the GPS signal and the replica signals in order to acquire the GPS signal.

8. The combination of a base station (BS1) and a mobile unit (MSl) for despreading a GPS spread spectrum signal received at a mobile unit with assistance from a base station;

wherein the base station comprises a GPS receiver (35) for receiving and despreading GPS signals at the base station and deriving GPS signal information therefrom, and a transmitter (31) for transmitting the modified GPS signal information from the base station to the mobile unit; and

wherein the mobile unit comprising a GPS receiver (24) for receiving the GPS signal;

a communications receiver (21) for receiving GPS signal information from a base station; and

a processor (26) arranged to modify the GPS signal information so as reflect the GPS signal characteristics as would be observed at an estimated location of the mobile unit, generate replica signals containing PRN codes corresponding to those of the GPS signal using the modified GPS signal information and perform a correlation of the GPS signal and the replica signals in order to acquire the GPS signal.

9. A base station for providing assistance to a mobile unit for despreading GPS spread spectrum signals received at the mobile unit comprising a GPS receiver for receiving and despreading GPS signals at the base station and deriving GPS signal information therefrom, a processor arranged to modify the GPS signal information so as reflect the GPS signal characteristics as would be observed at an estimated location of the mobile unit;

and a transmitter for transmitting the modified GPS signal information from the base station to the mobile unit.

10. A mobile unit for despreading a received GPS spread spectrum signal with assistance from a base station comprising a GPS receiver for receiving the GPS signal;

a communications receiver for receiving GPS signal information from a base station; and

a processor arranged to modify the GPS signal information so as reflect the GPS signal characteristics as would be observed at an estimated location of the mobile unit, generate replica signals containing PRN codes corresponding to those of the GPS signal using the modified GPS signal information and perform a correlation of the GPS signal and the replica signals in order to acquire the GPS signal.