System and method for generating pseudorandom numbers

• US 20050207574A1
• Filed: 03/19/2004
• Published: 09/22/2005
• Est. Priority Date: 03/19/2004
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Teutsch, Alexander, Cunningham, Nicole, Pitz, Jeanne Krayer
• Granted Patent: US 7,512,645 B2
• Time in Patent Office: Days
• US Class Current: 380/46
• CPC Class Codes: G06F 7/584 using finite field arithmetic, e.g. using a linear feedback shift register

Abstract

A system that has a pseudorandom number generator and a mapping system. The pseudorandom number generator generates a random number that is mapped by the mapping system to an output value that is selected from a set of predetermined output values. To increase the randomness of the sequence of numbers generated by the pseudorandom number generator, a tap and/or seed value of the pseudorandom number generator can be varied.

Claims

1. A system for generating a pseudorandom number, comprising:

a pseudorandom number generator; and

a mapping system that assigns each number generated by the pseudorandom number generator to an output value selected from a set of predetermined output values.

2. The system of claim 1, further comprising a programmable input for selecting the set of predetermined output values.

3. The system of claim 1, the pseudorandom number generator further comprising a linear feedback shift register that includes at least one feedback tap.

4. The system of claim 1, further comprising a tap selector system configured to set at least one tap of the pseudorandom number generator.

5. The system of claim 4, the tap selector system comprises a linear feedback shift register to pseudo-randomly set the at least one tap.

6. The system of claim 5, further comprising a seeding system configured to provide a seed to the linear feedback shift register.

7. The system of claim 6, the seeding system further comprising a second linear feedback shift register to pseudo-randomly provide the seed.

8. The system of claim 1, further comprising a seeding system configured to provide a pseudo-randomly generated seed to the pseudorandom number generator.

9. The system of claim 8, the seeding system further comprising a linear feedback shift register.

10. The system of claim 1, the mapping system being operative to

determine a plurality of substantially equal intervals based on a range of the numbers capable of being generated by the pseudorandom number generator and a number of elements in the set of predetermined output values;

and

to assign an output value from the set of predetermined output values to each of the intervals.

11. A system for generating a pseudorandom delay, comprising:

a first linear feedback shift register for generating a pseudorandom number, the first linear feedback shift register comprises at least one tap and a variable seed value; and

a mapping system configured to assign each pseudorandom number value to a corresponding coarse delay value, the coarse delay value associated with an interval from a plurality of substantially equal intervals based on a range of the first linear feedback register and a number of coarse delay values.

12. The system of claim 11, further comprising a tap selector linear feedback shift register to pseudo-randomly set the at least one tap of the first linear feedback shift register.

13. The system of claim 11, further comprising a seed selector linear feedback shift register to pseudo-randomly set the seed value of the first linear feedback shift register.

14. The system of claim 11, further comprising a second linear feedback shift register configured to provide a fine delay value, the fine delay value including a fractional portion of the coarse delay value.

15. The system of claim 14, further comprising a control for selecting an output delay from the group consisting of the coarse delay value, the fine delay value, and a combination of the coarse delay value and the fine delay value.

16. The system of claim 11, the mapping system configured to assign each pseudorandom number value to a corresponding coarse delay value and a fine delay value, the fine delay value including a fractional portion of the coarse delay value.

17. A system for generating a pseudorandom number, comprising:

means for producing a pseudorandom number; and

means for mapping the pseudorandom number to an output value selected from a set of output values.

18. The system of claim 17, the set of output values having fewer members than a set of possible values of the pseudorandom number.

19. The system of claim 17, further comprising means for pseudo-randomly changing at least one tap associated with the means for producing a pseudorandom number.

20. The system of claim 17, further comprising means for pseudo-randomly changing an initial seed value for the means for producing a pseudorandom number.

21. A system for generating a randomized delay for a plurality of devices where each device has an associated delay, each device comprising:

a pseudorandom number generator for generating a sequence of pseudorandom numbers, each pseudorandom number of the sequence of pseudorandom numbers corresponding to a delay factor, the pseudorandom number generator comprising;

a pseudorandom number generator for generating the sequence of pseudorandom numbers;

a mapping system for mapping each of the pseudorandom numbers to a one of a discrete number of delay values; and

a system for pseudo-randomly generating at least one of a tap setting value and a seed value for each sequence of pseudorandom numbers.

22. The system of claim 21, the pseudorandom number generator further comprising:

a first pseudorandom number generator for generating a coarse delay; and

a second pseudorandom number generator for generating a fine delay value, the fine delay value including a fractional portion of the coarse delay value.

23. A method, comprising:

pseudo-randomly generating a number within a predefined range of a plurality of numbers; and

mapping the pseudo-randomly generated number to an output value based on an interval associated with the pseudo-randomly generated number.

24. The method of claim 23, further comprising

determining a set of intervals for mapping the pseudo-randomly generated number by dividing a maximum range for a pseudorandom generator used to generate the pseudo-randomly generated number by a number of desired output values;

and

associating each output value with a corresponding interval from the set of intervals.

25. The method of claim 23, further comprising:

pseudo-randomly changing at least one of a tap and a seed value to increase the randomness of a sequence of numbers being generated.