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

• US 7,916,772 B2
• Filed: 06/14/2007
• Issued: 03/29/2011
• Est. Priority Date: 02/23/2000
• Status: Expired due to Fees

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Inventors: Rouphael, Antoine J., Nelson, George Jr., Proctor, James Jr., Hoffmann, John E.
• Primary Examiner(s): VO, DON NGUYEN
• Application Number:
  US11/818,293
• Publication Number:
  US 20080225991A1
• Time in Patent Office: 1,384 Days
• Field of Search: 375/267, 375/147, 375/152, 375/148, 375/149, 375/347
• US Class Current: 375/148
• 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 of searching for, and optimizing reception of, a pilot signal in wireless communications, comprising:

setting an antenna to an omnidirectional receiving pattern;

loading a frequency offset stored in an offset memory;

setting a pseudorandom number (PN) sequence offset to zero;

detecting a signal from the antenna;

comparing a magnitude of the signal to a first threshold;

on a condition that a PN epoch is beginning;

determining whether a valid pilot signal is present for the frequency offset, PN offset, and antenna receiving pattern; and

on a condition that a valid pilot signal is not detected, changing the frequency offset by a predetermined offset increment on a condition that the frequency offset is less than a second threshold,

and repeating the setting a PN sequence offset to zero; and

on a condition that a valid pilot signal is detected, ending the method; and

on a condition that a PN epoch is not beginning, repeating the comparing.

2. The method of claim 1, further comprising:

on a condition that the signal magnitude is greater than the first threshold, increasing the first threshold to a new first threshold; and

on a condition that the magnitude is less than the new first threshold, changing the PN offset by a predetermined offset increment.

3. The method of claim 1, further comprising:

on a condition that the signal magnitude exceeds a predetermined maximum threshold;

changing the receiving pattern of the antenna from omnidirectional to directional;

sweeping a reception angle of the antenna in predetermined increments;

determining a peak reception angle for the antenna at which the pilot signal is at its peak and storing the peak reception angle;

changing the PN offset by the predetermined offset increment; and

on a condition that a PN epoch is beginning, repeating the determining whether a valid pilot signal is present for the frequency offset, changed PN offset, and directional antenna receiving pattern.

4. The method of claim 1 further comprising:

on a condition that a valid pilot signal is not detected, adjusting the first threshold; and

repeating the detecting and comparing to the adjusted first threshold.

5. A wireless transmit/receive unit (WTRU) configured to search for, and optimize reception of, a pilot signal in wireless communications, comprising:

an antenna array;

steering circuitry configured to set the antenna array to a receiving pattern selected from a plurality of receiving patterns, wherein the plurality of receiving patterns includes an omnidirectional receiving pattern and directional receiving patterns;

an offset memory configured to store a frequency offset;

pseudorandom number (PN) sequence generation circuitry having a variable PN offset;

detection circuitry configured to detect a signal from the antenna array and compare a magnitude of the signal to a first threshold;

epoch processing circuitry configured to determine whether a PN epoch is beginning;

pilot signal circuitry configured to determine whether a valid pilot signal is present for the frequency offset, PN offset, and antenna receiving pattern; and

to end the searching on a condition that a pilot signal of a desired magnitude is detected, wherein the pilot signal circuitry operates on a condition that the epoch processing circuitry determines that a PN epoch is beginning; and

offset circuitry configured to change the frequency offset by a predetermined offset increment on a condition that a valid pilot signal is not detected, wherein the offset circuitry operates on a condition that the epoch processing circuitry determines that a PN epoch is beginning.

6. The WTRU of claim 5, further comprising threshold circuitry configured to increase the first threshold to a new first threshold on a condition that the signal magnitude is greater than the first threshold, the offset circuitry being further configured to change the PN offset by a predetermined offset increment on a condition that the magnitude is less than the new first threshold.

7. The WTRU of claim 5, wherein the steering circuitry is further configured to:

change the receiving pattern of the antenna from omnidirectional to directional on a condition that the signal magnitude exceeds a predetermined maximum threshold; and

sweep a reception angle of the antenna in predetermined increments.

8. The WTRU of claim 7, further comprising peak detection circuitry configured to determine a peak reception angle of the antenna at which angle the pilot signal is at its peak and to store the peak reception angle.

9. The WTRU of claim 6 wherein the threshold circuitry is further configured to adjust the first threshold on a condition that the pilot signal circuitry determines that a valid pilot signal is not detected.