Despreading spread spectrum data

• US 7,593,452 B1
• Filed: 08/11/2008
• Issued: 09/22/2009
• Est. Priority Date: 03/18/2008
• Status: Active Grant

• Current Assignee: Ingenu Inc.
• Original Assignee: On-Ramp Wireless Incorporated
• Inventors: Myers, Theodore J.
• Primary Examiner(s): DEPPE, BETSY LEE
• Application Number:
  US12/189,533
• Publication Number:
  US 20090238245A1
• Time in Patent Office: 407 Days
• Field of Search: 375/141, 375/12, 375/145, 375/147, 375/149, 375/150, 370/335, 370/342, 370/441, 370/320
• US Class Current: 375/147
• CPC Class Codes: H03J 7/02 Automatic frequency control H03J7/18 takes precedence
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70752 Partial correlation
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/0074 Code shifting or hopping
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04J 3/0685 Clock or time synchronisation in a node; Intranode synchronisation
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04L 7/0004 Initialisation of the receiver H04L7/0075 and H04L7/10 take precedence

Abstract

A method for de-spreading spread data includes receiving a data stream by multiple access communication where the received data stream is spread using a pseudo-noise (PN) code; multiplying a first portion of the received data stream including data from a first user by a first portion of a PN signal to obtain a first product; providing the first product to a first counter; multiplying a second portion of the received data stream including data from a second user by the first portion of the PN signal to obtain a second product; providing the second product to a second counter; and determining whether the first portion of the PN signal and the second portion of the PN signal produce valid sequences based at least in part on the first product and the second product.

Claims

1. A method for de-spreading spread data, the method comprising:

receiving a data stream by multiple access communication, wherein the spread data is spread using a pseudo-noise (PN) code;

multiplying a first portion of the received data stream including data from a first user by a first portion of a PN signal to obtain a first product;

providing the first product to a first counter;

multiplying a second portion of the received data stream including data from a second user by a second portion of the PN signal to obtain a second product;

providing the second product to a second counter; and

determining whether the first portion of the PN signal and the second portion of the PN signal produce valid sequences based at least in part on the first product and the second product.

2. The method of claim 1, wherein the spread data is spread using the PN code with a randomly selected chip offset.

3. The method of claim 2, further comprising determining whether the data stream is valid using a cyclic redundancy checking check.

4. The method of claim 1, further comprising iterating the PN signal over multiple spreading factors until valid sequences are determined.

5. The method of claim 1, wherein the second portion of the PN signal is obtained by imposing a delay on the first portion of the PN signal.

6. The method of claim 1, further comprising utilizing a plurality of contiguous timing hypothesis until valid sequences are determined.

7. The method of claim 1, further comprising iterating over fine automatic frequency control (AFC) hypothesis until valid sequences are determined.

8. A system for de-spreading spread data, the system comprising:

a first de-spread element comprising

a first combiner configured to multiply a first portion of a data stream from a first user by first portion of a pseudo-noise (PN) signal to obtain a first product, wherein the spread data is spread with a PN code; and

a first counter configured to receive the first product from the first combiner;

a second de-spread element comprising

a second combiner configured to multiply a second portion of the data stream from a second user by a second portion of the PN signal to obtain a second product; and

a second counter configured to receive the second product from the second combiner; and

a multiplexer configured to receive outputs of the first and second counters, wherein the multiplexer is used at least in part to determine whether the first portion of the PN signal and the second portion of the PN signal produce valid sequences based at least in part on the first product and the second product.

9. The system of claim 8, wherein the spread data is spread using the PN code with a randomly selected chip offset.

10. The system of claim 9, wherein the PN signal is iterated over multiple spreading factors until valid sequences are determined.

11. The system of claim 9, further comprising a delay module configured to impose a delay on the PN signal such that the second portion of the data stream is multiplied by the second portion of the PN signal.

12. The system of claim 8, wherein the first product is part of a first timing hypothesis and the second product is part of a second timing hypothesis.

13. The system of claim 12, wherein the first timing hypothesis and the second timing hypothesis are simultaneously determined.

14. An access point configured to de-spread spread data, the access point comprising:

a receiver configured to receive a data stream that is spread with a pseudo-noise (PN) code; and

a de-spreader in communication with the receiver, wherein the de-spreader comprises

a first de-spread element comprising

a first combiner configured to multiply a first portion of the data stream from a first user by a first portion of a pseudo-noise (PN) signal to obtain a first product; and

a first counter configured to receive the first product from the first combiner;

a second de-spread element comprising

a second combiner configured to multiply a second portion of the data stream from a second user by a second portion of the PN signal to obtain a second product; and

a second counter configured to receive the second product from the second combiner; and

a multiplexer configured to receive outputs of the first and second counters, wherein the multiplexer is used at least in part to determine whether the first portion of the PN signal and the second portion of the PN signal produce valid sequences based at least in part on the first product and the second product.

15. The access point of claim 14, wherein the data stream is spread using the PN code with a randomly selected chip offset.

16. The access point of claim 14, wherein the de-spreader further comprises a delay module configured to impose a delay on the PN signal such that the second portion of the data stream is multiplied by the second portion of the PN signal.

17. The access point of claim 14, wherein the first product is part of a first timing hypothesis and the second product is part of a second timing hypothesis, and further wherein the first timing hypothesis and the second timing hypothesis are a chip apart.

18. The access point of claim 14, wherein the PN signal is iterated over multiple spreading factors until valid sequences are determined.