Systems and methods for rapid uplink air interface synchronization

• US 8,259,777 B2
• Filed: 01/09/2007
• Issued: 09/04/2012
• Est. Priority Date: 11/30/2006
• Status: Expired due to Fees

• Current Assignee: Adaptix, Inc. (Acacia Research Corporation)
• Original Assignee: Adaptix, Inc. (Acacia Research Corporation)
• Inventors: Li, Xuan, Shen, Manyuan, Xing, Guanbin
• Primary Examiner(s): Corrielus, Jean B
• Application Number:
  US11/651,239
• Publication Number:
  US 20080130766A1
• Time in Patent Office: 2,065 Days
• Field of Search: 375/130, 375/142, 375/140, 375/371, 375/150, 370/516, 370/519, 370/480, 455/522
• US Class Current: 375/142
• CPC Class Codes: H04L 27/261 Details of reference signals
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Rapid uplink synchronization is enabled by reducing a 2D search problem to two 1D search problems, which can generally be performed in less time. Advantage is taken of fact that a mobile device sends a ranging code on multiple sub-carriers. Using the assumption that adjacent sub-carriers will have approximately equivalent channel characteristics, phase ambiguity can be removed by differentially combining pairs of adjacent sub-carriers. Once the phase ambiguity is removed, the code, timing, and power level may be determined relatively quickly. In one embodiment, the values of correlations between received signals and possible codes are compared with a threshold.

Claims

1. A method of establishing an air interface communication between a base station and a mobile device, said method comprising:

removing phase ambiguity from ranging signals transmitted by said mobile device and received at said base station, said removing producing differential ranging sub-carriers; and

after said phase ambiguity has been removed, correlating said ranging signals with possible ranging codes, wherein said correlating comprises;

multiplying said differential ranging sub-carriers with one or more local replicas of possible differential ranging codes;

summing the results of said multiplying, said summing producing one or more correlation values between said local replicas and said ranging signals transmitted by said mobile device;

calculating power levels of said one or more correlation values;

selecting a set of correlation values from said one or more correlation values, wherein each of said selected set of correlation values have a power level that exceeds a predetermined threshold;

calculating a power adjustment value for said mobile device by comparing said power levels of said selected set of correlation values with a target power; and

providing to said mobile device information based on said power adjustment value.

2. The method of claim 1 further comprising:

after said correlating said ranging signals with said possible ranging codes, calculating a propagation time of said air interface communication between said mobile device and said base station.

3. The method of claim 2 wherein said calculating said propagation time comprises:

phase detection.

4. The method of claim 2 wherein said calculating said propagation time comprises a method selected from the list including:

inverse Fast Fourier Transform (FFT) and sine wave correlation.

5. The method of claim 1 wherein said removing phase ambiguity comprises:

differentially multiplying adjacent ranging sub-carriers.

6. The method of claim 1 further comprising:

after said correlating said ranging signals with said possible ranging codes, instructing said mobile device to increase transmission power of said mobile device if none of said power levels exceed said predetermined threshold.

7. The method of claim 1 for use in an orthogonal frequency division multiple access (OFDMA) system.

8. The method of claim 1 for use in an orthogonal frequency division multiplexing (OFDM) system.

9. The method of claim 1, further comprising:

calculating an identifying code from said ranging signals;

wherein said calculating includes calculating a highest correlation value of said correlation values and, if said highest correlation value exists, identifying a member of said local replica of possible ranging codes corresponding to said highest correlation value.

10. The method of claim 9, further comprising:

instructing said mobile device to increase transmission power if no ranging signal is identified from said identifying.

11. An air interface communication system comprising:

a base station including at least one processor, said at least one processor adapted for removing phase ambiguity from ranging signals transmitted by a mobile device, said removing producing differential ranging sub-carriers, and,

after said phase ambiguity has been removed, correlating said ranging signals with possible ranging codes, wherein said correlating comprises;

multiplying said differential ranging sub-carriers with one or more local replicas of possible differential ranging codes;

summing the results of said multiplying, said summing producing one or more correlation values between said local replicas and said ranging signals transmitted by said mobile device;

calculating power levels of said one or more correlation values;

selecting a set of correlation values from said one or more correlation values, wherein each of said selected set of correlation values has a power level that exceeds a predetermined threshold; and

calculating a power adjustment value for said mobile device by comparing said power levels of said selected set of correlation values with a target power.

12. The system of claim 11 wherein said at least one processor is further adapted for:

after said correlating said ranging signals with said possible ranging codes, calculating a propagation time of air interface communication between said mobile device and said base station.

13. The system of claim 12 wherein said calculating said propagation time uses phase detection.

14. The system of claim 12 wherein said calculating said propagation time uses one of:

inverse Fast Fourier Transform (FFT) and sine wave correlation.

15. The system of claim 11 wherein said removing phase ambiguity includes differentially multiplying adjacent ranging sub-carriers.

16. The system of claim 11 further comprising:

after said correlating said ranging signals with said possible ranging codes, instructing said mobile device to increase transmission power of said mobile device if said power level does not exceed said predetermined threshold.

17. The system of claim 11 wherein said air interface communication system is an orthogonal frequency division multiple access (OFDMA) system.

18. The system of claim 11 wherein said air interface communication system is an orthogonal frequency division multiplexing (OFDM) system.

19. A method comprising:

extracting received ranging sub-carriers from a signal transmitted by a mobile device;

differentially multiplying adjacent ranging sub-carriers of said received ranging sub-carriers;

multiplying said result of said differentially multiplying with one or more local replicas of possible differential ranging codes;

summing the results of said multiplying, said summing resulting in one or more correlation values between said local ranging codes and said received ranging sub-carriers;

selecting a range of transmitted ranging codes from said received ranging sub-carriers, wherein each ranging code of said selected range of said transmitted ranging codes has a power exceeding predetermined threshold, said power being calculated from said one or more correlation values corresponding to said received ranging sub-carriers;

comparing each of said power of each of said selected range of said transmitted ranging codes with a target power;

calculating power adjustment values for said mobile device based on said comparing; and

providing to said mobile device information based on said power adjustment values.

20. A base station comprising:

at least one processor configured for;

extracting received ranging sub-carriers from a signal transmitted by a mobile device;

differentially multiplying adjacent ranging sub-carriers of said received ranging sub-carriers;

multiplying said result of said differentially multiplying with one or more local replicas of possible differential ranging codes stored in memory;

summing the results of said further multiplying, said summing resulting in one or more correlation values;

selecting a range of transmitted ranging codes from said received ranging sub-carriers, wherein each ranging code of said selected range of said transmitted ranging codes has a power exceeding predetermined threshold, said power being calculated from said one or more correlation values corresponding to said received ranging sub-carriers;

comparing each of said power of each of said selected range of said transmitted ranging codes with a target power; and

calculating power adjustment values for said mobile device based on said comparing.