Method and apparatus for implementing PN masks for a truncated M-sequence

• US 6,246,676 B1
• Filed: 12/13/1999
• Issued: 06/12/2001
• Est. Priority Date: 12/13/1999
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Rotstein, Ron, Chen, Jiangnan, Luz, Yuda Y.
• Primary Examiner(s): Patel, Ajit
• Application Number:
  US09/459,688
• Time in Patent Office: 547 Days
• Field of Search: 370/328, 370/335, 370/342, 370/431, 370/340, 370/441, 375/130, 375/140, 375/141-145
• US Class Current: 370/342
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/0074 Code shifting or hopping
• CPC Class Codes: H04J 13/10 Code generation

Abstract

Method and apparatus to provide a pseudo random noise (PN) sequence having a particular code phase offset for use in a radio in a Code Division Multiple Access (CDMA) radio system (100). In one embodiment, a first mask (320) is applied to shift a reference PN sequence to the assigned PN code phase (416). Upon reaching the end of the reference PN sequence, the initial state is reloaded (420) into the PN generator state register to reset the state value to its initial value, thereby producing a cyclical sequence. In a second embodiment, a first mask (622) and a second mask (624) are applied to the reference sequence produced by the PN generator state registers (620) to produce the appropriate portions of the output sequence.

Claims

1. A method for providing a pseudo random noise (PN) sequence having a particular phase offset, the method comprising:

(a) starting at a state of a reference PN sequence corresponding to the particular phase offset, generating a PN symbol;

(b) shifting the PN symbol to produce a shifted PN symbol;

(c) generating a next PN symbol of the PN sequence;

(d) repeating steps (b)-(c) to produce the PN sequence; and

(e) when a difference between a length of the reference PN sequence and an offset value corresponding to the particular phase offset substantially matches a sequence position, returning to an initial state of the reference PN sequence.

2. The method of claim 1 further comprising:

(f) incrementing the sequence position for each PN symbol;

(g) when the sequence position substantially matches the length of the reference PN sequence, resetting the sequence position.

3. The method of claim 1 further comprising:

receiving initial state of the reference PN sequence; and

receiving the offset value corresponding to the particular phase offset.

4. The method of claim 1 wherein shifting the PN symbol comprises:

applying a mask to the PN symbol to produce the shifted PN symbol, the mask corresponding to the particular phase offset.

5. The method of claim 4 further comprising:

receiving the mask.

6. The method of claim 1 wherein the reference PN sequence is non-cyclical.

7. The method of claim 6 wherein the reference PN sequence is a truncated cyclical PN sequence.

8. A radio comprising:

a processor which controls the radio;

a pseudo random noise (PN) generator configured to generate a PN symbol, the PN symbol being one element of a reference PN sequence;

a masking circuit coupled to the PN generator and configured to shift the PN symbol to produce a shifted PN symbol corresponding to a particular PN phase offset;

a comparator configured to produce a signal when a difference between a length of the reference PN sequence and an offset value corresponding to the particular PN phase offset substantially matches a sequence position; and

a storage circuit configured to store an initial state of the reference PN sequence and transfer the original state of the reference PN sequence to the PN generator in response to the signal.

9. The radio of claim 8 further comprising a counter which stores the sequence position.

10. The radio of claim 9 further comprising a clock circuit generating a clock signal to increment the counter for each PN symbol generated by the PN symbol generator.

11. The radio of claim 10 further comprising;

a second comparator configured to produce a second signal when the sequence position substantially matches the length of the reference PN sequence,

the counter configured to be reset to an initial value in response to the second signal.

12. The radio of claim 11 wherein the radio comprises a mobile station of a Code Division Multiple Access radio system.

13. The radio of claim 11 wherein the radio comprises a base station of a Code Division Multiple Access radio system.

14. A method for generating a particular pseudo random noise (PN) code phase in a code division multiple access (CDMA) radio, the method comprising:

receiving initial values corresponding to the particular PN code phase;

generating PN symbols starting at a first state of a reference PN sequence and continuing through the reference PN sequence;

shifting the PN symbols to form shifted PN symbols which correspond to states of the particular PN code phase; and

when a difference between a length of the reference PN sequence and an offset value corresponding to the particular PN code phase substantially matches a sequence position, generating the PN symbols by again starting at the first state of the reference PN sequence.

15. The method of claim 14 wherein receiving the initial values comprises:

receiving the first state of the reference PN sequence;

receiving the offset value; and

receiving a mask for shifting the PN symbols in correspondence with the particular PN code phase.

16. The method of claim 14 further comprising:

upon generation of each PN symbol, incrementing a count of sequence position; and

when the count of sequence position substantially matches the length of the reference PN sequence.

17. A method for providing a pseudo random noise (PN) sequence having a particular phase offset, the method comprising:

(a) starting at an initial state of a reference PN sequence corresponding to the particular phase offset, generating a PN symbol;

(b) applying a first mask and producing a shifted PN symbol as one element of the PN sequence;

(c) repeating steps (a) and (b) until a final element of the reference PN sequence is reached;

(d) applying a second mask and producing the shifted PN symbol as one element of the PN sequence; and

(e) when an element of the reference PN sequence corresponding to the initial state of the reference PN sequence is reached,

applying the first mask, and

returning to step (a) to continue producing the PN sequence.

18. The method of claim 17 further comprising:

incrementing a sequence position counter;

when contents of the sequence position counter substantially matches the difference between a length of the reference PN sequence and an offset corresponding to the particular phase offset, applying the second mask.

19. The method of claim 18 further comprising:

comparing contents of the sequence position counter and the offset corresponding to the particular phase offset;

when the contents of the sequence position counter substantially match the offset, applying the first mask and returning to step (a).

20. A radio comprising:

a pseudo random noise (PN) generator configured to generate a PN synbol, the PN symbol being one element of a reference PN sequence, the PN generator having an initial state related to a particular PN code phase assigned to the radio and a final state;

a first masking circuit coupled to the PN generator and configured to shift the PN symbol a first predetermined amount to produce a shifted PN symbol corresponding to a particular PN phase offset;

a second masking circuit coupled to the PN generator and configured to shift the PN symbol a second predetermined amount to produce a shifted PN symbol corresponding to a particular PN phase offset;

a switching circuit configured to selectively couple one of the first masking circuit and the second masking circuit to an output in response to a control signal; and

a comparing circuit coupled to the switching circuit which generates the control signal in response to the relative state of the PN generator between the initial state and the final state.

21. The radio of claim 20 wherein the comparing circuit comprises:

a counter which stores sequence position;

a comparator which generates the control signal in response to comparison of contents of the counter and a difference between a length of the reference PN sequence and an offset corresponding to the particular PN code phase assigned to the radio.

22. The radio of claim 20 wherein the radio comprises a base station of a Code Division Multiple Access radio system.

23. The radio of claim 20 wherein the radio comprises a mobile station of a Code Division Multiple Access radio system.