Random access preamble coding for initiation of wireless mobile communications sessions

• US 7,324,485 B2
• Filed: 06/08/2004
• Issued: 01/29/2008
• Est. Priority Date: 06/11/1999
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Dabak, Anand G.
• Primary Examiner(s): Ryman; Daniel J.
• Application Number:
  US10/864,680
• Publication Number:
  US 20040264550A1
• Time in Patent Office: 1,330 Days
• Field of Search: None
• US Class Current: 370/335
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04J 13/0048 Walsh
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes
• CPC Class Codes: H04L 7/041 using special codes as synchronising signal

Abstract

A method of operating a wireless communications unit (UE) to request a connection with a base station (10) is disclosed. The wireless unit (UE) receives a signal from the base station (10) indicating at least one time slot within which a preamble may be transmitted by the wireless communications unit (UE). The wireless unit (UE) selects one of a plurality of orthogonal codes (h_i) for the preamble and generates a spread code using the selected orthogonal code. The spread code (70) is arranged as a symbol (h_i) of the selected code, repeated a selected number of repetitions. The wireless unit (UE) transmits the preamble signal corresponding to the spread code to the base station (10).

Claims

1. A method of decoding a preamble, comprising the steps of:

extracting a first number of groups of signals having a second number of signals in each group from a data stream having a predetermined length, wherein each group has a third number of subgroups;

applying one signal from each subgroup to a respective despreader circuit of a third number of despreader circuits, each despreader circuit producing a respective output signal; and

producing at least one transform from the output signals from the third number of despreader circuits, the at least one transform having the third number of signals.

2. A method as in claim 1, comprising summing a respective signal corresponding to the at least one transform at a third number of sum circuits, thereby producing the third number of sum signals.

3. A method as in claim 2, wherein a product of the first and second numbers is equal to the predetermined length.

4. A method as in claim 3, wherein the first number is 4, the second number is 1024, the third number is 16, and the predetermined length is 4096 signals.

5. A method as in claim 2, wherein the at least one transform is a Walsh Hadamard transform.

6. A method as in claim 2, wherein the respective signal corresponding to the at least one transform is a square of the amplitude of the transform signal.

7. A method as in claim 2, wherein the sum signal corresponds to a match between the data stream and one of a plurality of codes.

8. A method as in claim 1, comprising:

producing a plurality of products, each product comprising a respective transform signal and complex conjugates of another respective transform signal; and

summing a plurality of the products at each of a third number of sum circuits, thereby producing the third number of sum signals.

9. A method as in claim 8, wherein a product of the first and second numbers is equal to the predetermined length.

10. A method as in claim 9, wherein the first number is 4, the second number is 1024, the third number is 16, and the predetermined length is 4096 signals.

11. A method as in claim 8, wherein the at least one transform is a Walsh Hadamard transform.

12. A method as in claim 8, wherein the sum signal corresponds to a match between the data stream and one of a plurality of codes.

13. A method of decoding a data sequence having a group of signals repeated a predetermined number of times, comprising the steps of:

applying one signal from each group to a respective despreader circuit of a plurality of despreader circuits, each despreader circuit of the plurality of despreader circuits producing a respective output signal; and

producing at least one transform from the output signals of the plurality of despreader circuits, the at least one transform having a second number of signals.

14. A method as in claim 13, wherein the plurality of despreader circuits comprises 64 despreader circuits.

15. A method as in claim 13, wherein the at least one transform comprises 4 transforms.

16. A method as in claim 13, wherein the at least one transform is a Walsh Hadamard transform.

17. A method as in claim 13, comprising summing a respective signal corresponding to the at least one transform at a respective sum circuit, thereby producing a plurality of sum signals, wherein the plurality of sum signals corresponds to a match between the group of signals and one of a plurality of codes.

18. A method as in claim 13, comprising summing a respective signal corresponding to the at least one transform at a respective sum circuit, thereby producing a plurality of sum signals.

19. A method as in claim 13, comprising:

producing a plurality of products, each product comprising a respective transform signal and complex conjugates of another respective transform signal; and

summing a plurality of the products at each of a plurality of sum circuits, thereby producing a plurality of sum signals.

20. A method of communicating with a remote device, comprising the steps of:

selecting a first code from a plurality of orthogonal codes;

repeating the first code a plurality of times to produce a sequence having a predetermined length;

combining the sequence with a second code having the predetermined length to produce a preamble;

transmitting the preamble to the remote device; and

receiving an acknowledgement from the remote device in response to the step of transmitting.

21. A method as in claim 20, wherein the plurality of orthogonal codes are Walsh Hadamard codes corresponding to users in a wireless cell and wherein the second code is a scrambling code corresponding to a wireless cell.