Spread spectrum with doppler optimization

• US 7,733,945 B2
• Filed: 05/27/2009
• Issued: 06/08/2010
• Est. Priority Date: 03/18/2008
• Status: Active Grant

• Current Assignee: Ingenu Inc.
• Original Assignee: On-Ramp Wireless Incorporated
• Inventors: Myers, Theodore J., Werner, Daniel Thomas
• Primary Examiner(s): BURD, KEVIN MICHAEL
• Application Number:
  US12/472,642
• Publication Number:
  US 20090238248A1
• Time in Patent Office: 377 Days
• Field of Search: 375/130, 375/140, 375/142, 375/147, 375/150
• US Class Current: 375/149
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase

Abstract

A method of compensating for doppler phase errors includes receiving a signal at a receiver wherein the signal is spread using a pseudo-noise code, dividing the signal into a plurality of smaller coherent units and then compensating for induced doppler phase errors by analyzing the plurality of smaller coherent units. Analysis may include producing a plurality of coherent sums by summing across the smaller coherent units and then summing non-coherently the plurality of coherent sums. Analysis may also include demodulating a symbol from the smaller coherent units. A modulation technique may be selected from a plurality of modulation techniques and then be used to encode and transmit a symbol stream.

Claims

1. A method of compensating for induced doppler phase errors while communicating through a multiple access spread spectrum communication interface, the method comprising:

receiving a first signal at a receiver, wherein the first signal is spread using a predetermined pseudo-noise (PN) code;

dividing the first signal into a plurality of first smaller coherent units;

summing across each of the plurality of first smaller coherent units to produce a plurality of first coherent sums;

summing non-coherently the plurality of first coherent sums to detect a magnitude of the first signal;

selecting a coherent integration length based on the magnitude of the first signal to configure a demodulation;

receiving a second signal at the receiver, wherein the second signal is spread using the predetermined pseudo-noise (PN) code;

dividing the second signal into a plurality of second smaller coherent units; and

demodulating a first symbol from the plurality of first smaller coherent units and the plurality of second smaller coherent units comprises cross multiplying the complex conjugate of a unit of the first smaller coherent units with a unit of the second smaller coherent units.

2. The method of claim 1, wherein the demodulation of the first symbol relies on a first unit of the plurality of first smaller coherent units and a last unit of the plurality of second smaller coherent units.

3. The method of claim 1, wherein the first signal neighbors the second signal in a sequence of signals.

4. The method of claim 1, wherein the first signal has a first random timing offset.

5. The method of claim 1, wherein the second signal has a second random timing offset.

6. The method of claim 1, further comprising:

detecting an induced doppler phase error in the first signal;

selecting a modulation technique from a plurality of modulation techniques from among the following modulation techniques;

differential binary phase shift keyed modulation or 2-ary modulation;

encoding a symbol stream using the selected modulation technique; and

transmitting the encoded symbol stream.

7. The method of claim 6, further wherein the selected modulation technique is based on the detected induced doppler phase error.

8. The method of claim 6, further comprising:

selecting a second modulation technique from the plurality of modulation techniques; and

encoding a second symbol stream using the selected second modulation technique.

9. A device for communicating in a spread spectrum system comprising:

a receiver in communication with a processor and configured to receive a first signal and a second signal, wherein the first signal is spread using a predetermined pseudo-noise (PN) code and the second signal is spread using the predetermined pseudo-noise (PN) code; and

a processor operatively coupled to the receiver and configured to;

divide the first signal into a plurality of first smaller coherent units,

sum across each of the plurality of first smaller coherent units to produce a plurality of first coherent sums;

sum non-coherently the plurality of first coherent sums to detect a magnitude of the first signal;

select a coherent integration length based on the magnitude of the first signal to configure a demodulation;

divide the second signal into a plurality of second smaller coherent units; and

demodulate a first symbol from the plurality of first smaller coherent units and the plurality of second smaller coherent units comprises cross multiplying the complex conjugate of a unit of the first smaller coherent units with a unit of the second smaller coherent units.

10. The device of claim 9, wherein the first signal has a first random timing offset.

11. A spread spectrum communication system comprising:

a device having a receiver configured to receive a first signal and a second signal, wherein the first signal is spread using a predetermined pseudo-noise (PN) code and the second signal is spread using the predetermined pseudo-noise (PN) code; and

a processor operatively coupled to the receiver and configured to;

divide the first signal into a plurality of first smaller coherent units;

sum across each of the plurality of first smaller coherent units to produce a plurality of first coherent sums;

sum non-coherently the plurality of first coherent sums to detect a magnitude of the first signal;

select a coherent integration length based on the magnitude of the first signal to configure a demodulation;

divide the second signal into a plurality of second smaller coherent units; and

demodulate a first symbol from the plurality of first smaller coherent units and the plurality of second smaller coherent units comprises cross multiplying the complex conjugate of a unit of the first smaller coherent units with a unit of the second smaller coherent units; and

an access point in communication with the device, wherein the access point comprises a transmitter configured to transmit the first signal.

12. The system of claim 11, wherein the first signal has a first random timing offset.