METHOD FOR SEARCHING PILOT SIGNALS TO SYNCHRONIZE A CDMA RECEIVER WITH AN ASSOCIATED TRANSMITTER

• US 20110170493A1
• Filed: 03/28/2011
• Published: 07/14/2011
• Est. Priority Date: 02/23/2000
• Status: Active Grant

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Inventors: Nelson, George R. JR., Proctor, James A. JR., Rouphael, Antoine J., Hoffmann, John E.
• Granted Patent: US 8,315,294 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• 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. An apparatus for searching for a pilot signal and optimizing reception of the pilot signal in wireless communications, comprising:

a steerable antenna comprising a plurality of antenna elements;

phase shifters coupled to respective antenna elements, the phase shifters configured to steer the antenna;

a pseudorandom noise (PN) sequence generator, configured to generate a PN sequence as output;

a modulator, configured to receive demodulated in-phase (I) and quadrature (Q) signals and modulate the I and Q signals with the output of the PN sequence generator;

a first integrator configured to integrate the modulated I signal;

a second integrator configured to integrate the modulated Q signal;

a first squarer configured to square an output of the first integrator;

a second squarer configured to square an output of the second integrator;

a summer configured to add outputs of the first and second squarers;

a third integrator configured to integrate an output of the summer; and

a threshold circuit configured to set a plurality of thresholds and determine if an output of the third integrator exceeds at least one of the thresholds.

2. The apparatus of claim 1, further comprising:

a first memory configured to store a phase angle;

a digital-to-analog converter configured to receive the phase angle and supply antenna direction setting information to the phase shifters;

a second memory configured to store a frequency offset;

a frequency incrementing circuit configured to increment the frequency offset by a predetermined offset increment; and

a PN offset circuit configured to apply a PN offset to the PN sequence from the PN sequence generator;

wherein the apparatus detects the pilot signal by incrementing the frequency offset, incrementing the PN offset, and comparing the output of the third integrator to the thresholds, and maximizes a magnitude of the detected pilot signal by steering the antenna.

3. A wireless transmit/receive unit (WTRU) comprising:

an adaptive antenna configured to have a receiving pattern adaptable to be directional or omnidirectional;

steering circuitry configured to;

adapt the receiving pattern into the directional or the omnidirectional receiving pattern; and

steer a direction of the directional pattern over a range of azimuth angles;

detection circuitry configured to detect a pseudorandom (PN) offset of a pilot signal received by the antenna while the antenna is adapted to the omnidirectional receive pattern; and

monitoring circuitry configured to monitor a received signal strength of the pilot signal as the directional receive pattern is steered in order to determine a maximizing azimuth angle of the directional pattern for receiving the pilot signal at the detected PN offset.

5. The WTRU of claim 5, wherein the detection circuitry is further configured to detect the PN offset of the pilot signal by using a method comprising:

searching a set of PN offsets at an initial frequency;

if no pilot signal is detected,

stepping through one or more frequency bins; and

scanning the set of PN offsets at each of the one or more frequency bins until a pilot signal is detected.

4. The WTRU of claim 5, wherein the steering circuitry is further configured to adapt the antenna to a directional receive pattern at an azimuth angle that maximizes the received signal strength of the pilot signal.

6. A wireless transmit/receive unit (WTRU) comprising:

a receiver;

an adaptive antenna connected to the receiver and configured to have a receiving pattern adaptable to be directional or omnidirectional;

steering circuitry configured to;

adapt the receiving patter into a directional or an omnidirectional receiving pattern; and

steer a direction of the directional pattern over a range of azimuth angles;

detection circuitry configured to detect a plurality of PN offsets of a multipath pilot signal received by the antenna while the antenna is adapted to the omnidirectional receive pattern;

monitoring circuitry configured to monitor, for each PN offset of the plurality of PN offsets, a received signal strength of the pilot signal as the directional receive pattern is steered in order to determine a maximizing azimuth angle of the directional pattern for maximizing a received signal strength of the pilot signal at that detected PN offset; and

synchronization circuitry configured to synchronize the receiver to a selected one of the plurality of PN offsets and further adapting the antenna to a directional receive pattern at an azimuth angle that produces a maximal signal strength of the pilot signal.