Systems and methods for rapid uplink air interface synchronization

• US 20080130766A1
• Filed: 01/09/2007
• Published: 06/05/2008
• Est. Priority Date: 11/30/2006
• Status: Active Grant

• Current Assignee: Adaptix, Inc. (Acacia Research Corporation)
• Original Assignee: Adaptix, Inc. (Acacia Research Corporation)
• Inventors: Li, Xuan, Xing, Guanbin, Shen, Manyuan
• Granted Patent: US 8,259,777 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• 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

11. An air interface communication system comprising:

means for removing phase ambiguity from ranging signals transmitted over a plurality of sub-carrier signals by said mobile device and received at said base station; and

means for, when said phase ambiguity has been removed, determining identifying codes sent by said mobile device.

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 over a plurality of sub-carrier signals by said mobile device and received at said base station; and

when said phase ambiguity has been removed, determining identifying codes sent by said mobile device.

2. The method of claim 1 further comprising:

determining a propagation time between said mobile device and said base station; and

determining an acceptable power level for air interface communication between said base station and said mobile device.

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

phase detection.

4. The method of claim 2 wherein said determining a 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 wherein said determining identifying codes comprises:

correlating said signals with possible codes; and

comparing correlated values with a threshold.

7. The method of claim 6 wherein said correlating comprises:

multiplying said sub-carriers with local replicas of said possible codes; and

summing results of said multiplication.

8. The method of claim 1 further comprising:

instructing said mobile device to increase transmission power if no identifying code is determined.

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

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

12. The system of claim 11 further comprising:

means for determining a propagation time between said mobile device and said base station; and

means for determining an acceptable power level for air interface communication between said base station and said mobile device.

13. The system of claim 12 wherein said means for determining a propagation time uses phase detection.

14. The system of claim 12 wherein said means for determining a propagation time uses one of:

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

15. The system of claim 11 wherein said means for removing phase ambiguity comprises:

means for differentially multiplying adjacent ranging sub-carriers.

16. The system of claim 11 wherein said means for determining identifying codes comprises:

means for correlating said signals with possible codes; and

means for comparing correlated values with a threshold.

17. The system of claim 16 wherein said means for correlating comprises:

means for multiplying said sub-carriers with local replicas of said possible codes; and

means for summing results of said multiplication.

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

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

17-1. The system of claim 11 further comprising:

means for instructing said mobile device to increase transmission power if no identifying code is determined.