Method for searching pilot signals to synchronize a CDMA receiver with an associated transmitter

• US 20020136274A1
• Filed: 02/20/2001
• Published: 09/26/2002
• Est. Priority Date: 02/23/2000
• Status: Active Grant

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: Tantivy Communications Incorporated (InterDigital, Inc.)
• Inventors: Rouphael, Antoine J., Hoffmann, John E., Proctor, James A., Nelson, George Rodney Jr.
• Granted Patent: US 7,233,627 B2
• Time in Patent Office: Days
• US Class Current: 375/142
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70775 Multi-dwell schemes, i.e. multiple accumulation times
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04L 2027/0057 quadrature phase
• CPC Class Codes: H04L 2027/0087 Out-of-band signals, (e.g. pilots)
• CPC Class Codes: H04L 27/2273 associated with quadrature demodulation, e.g. Costas loop
• CPC Class Codes: H04W 56/001 Synchronization between nodes

Abstract

A method for synchronizing a CDMA receiver to a transmitter when an adaptive antenna is utilized to receive transmitted data, wherein a receiving antenna system is adapted between a 360° reception angle pattern (i.e., an omni-directional pattern) and a fixed reception angle (i.e., a directional pattern) by permitting the receiver to identify a pilot signal having the largest magnitude. The receiver minimizes interference from other pilot signals by steering antenna pattern nulls toward other transmitters. As a result, the time required for the receiver to acquire a valid pilot signal is significantly reduced.

Claims

1. A method for synchronizing a receiver having an adaptive antenna to a transmitter, comprising the steps of:

adapting the antenna to an omni-directional pattern;

checking PN offsets of a transmitted pilot signal;

storing PN offsets of the transmitted pilot signal which produce valid correlations of PN offsets;

reloading each PN offset which produced the valid correlations of PN offsets;

steering the antenna to a directional pattern; and

monitoring a correlation value of the PN offset which produced a valid correlation of a PN offset while adapting the antenna to the directional pattern to synchronize the receiver to a strongest transmitted pilot signal.

2. The method of claim 1, wherein said adapting step comprises the step of:

steering an azimuth angle of the antenna to provide specified phase angles with respect to each element in the antenna.

3. The method of claim 1, wherein said steering an azimuth angle comprises the steps of:

setting a phase angle of perimeter elements of the antenna to zero phase; and

setting the phase angle of a middle element of the antenna to ninety degrees.

4. The method of claim 3, wherein said step of setting the phase angle comprises the steps of:

utilizing a digital to analog convertor to up-load the specified phase angles to a respective phase shifter attached to each antenna element such that the antenna system points toward a specific corresponding angle.

5. The method of claim 1, wherein said steering step comprises:

adjusting an azimuth angle of the antenna across a predefined range;

monitoring a magnitude of the correlation value at the PN offset which produced the valid correlation of the PN offset; and

determining the azimuth angle which produces a maximum correlation value at the PN offset which produced the valid correlation of the PN offset.

6. The method of claim 2, wherein the predefined range is from 0 to 360 degrees.

7. The method of claim 5, further comprising the steps of:

generating a table of PN offsets and azimuth angles which produce maximum correlation values at each PN offset which produced valid correlations of PN offsets;

searching the table to locate a PN offset and an azimuth angle having the maximum correlation value; and

reloading the PN offset and azimuth angle having the maximum correlation value.

8. The method of claim 1, wherein said checking step comprises the steps of:

comparing a threshold of the PN offsets to a predetermined value.