Method, apparatus and software for verifying a parameter value against a predetermined threshold function

1. A computer-implemented method for verifying a parameter value against a predetermined threshold function, said method comprising the steps of:

a) retrieving a sequence of three reference values, each reference value being associated with respective time based sampling points N−1, N and N+I, said reference values representing a threshold function at said respective sampling points N−1, N and N+I;

b) associating a profile type with said threshold function;

c) receiving a parameter value for verification against said threshold function, said parameter value being associated with a discrete time P;

d) combining at least some of said sequence of reference values with said profile type to provide an approximation of said threshold function for a region of said threshold function between said reference values; and

e) verifying said parameter value against said approximation of said threshold function.

2. A method according to claim 1 in which said sequence of reference values comprises three reference values but in step d) only the two reference values associated with sampling points N closest to said time P are combined with said profile type.

3. A method according to claim 2 in which said method comprises a further step of comparing said time P to said sampling points and if N<=P<=N+1, then replacing said reference value N−1 with a new reference value N+2 for use with a subsequently received parameter value.

4. A method according to claim 2 in which said method comprises a further step of comparing said time P to said sampling points and if P<N+1, then replacing said sequence with a further sequence of reference values N′−1, N′ and N′+1 for use in step e).

5. An apparatus for verifying a parameter value against a predetermined threshold function, said apparatus being configured to:

retrieve a sequence of three reference values, each reference value being associated with respective time based sampling points N−1, N and N+1, said reference values representing a threshold function at said respective sampling points N−1, N and N+1;

associate a profile type with said threshold function;

receive a parameter value for verification against said threshold function, said parameter value being associated with a discrete time P;

combine at least some of said sequence of reference values with said profile type to provide an approximation of said threshold function for a region of said threshold function between said reference values; and

verify said parameter value against said approximation of said threshold function.

6. An apparatus according to claim 5 in which said sequence of reference values comprises three reference values but only the two reference values associated with sampling points N closest to said time P are combined with said profile type.

7. An apparatus according to claim 6 in which said apparatus is further configured to compare said time P to said sampling points and if N<=P<=N+1, then replace said reference value N−1 with a new reference value N+2 for use with a subsequently received parameter value.

8. An apparatus according to claim 6 in which said apparatus is further configured to compare said time P to said sampling points and if P<N+1, then replace said sequence with a further sequence of reference values N′−1, N′ and N′+1 for use in verifying said parameter value against said approximation of said threshold function.

9. A computer-readable medium with program code embodied therein for causing when executed, a computer system, to perform a method of:

a) retrieving a sequence of three reference values, each reference value being associated with respective time based sampling points N−1, N and N+1, said reference values representing a threshold function at said respective sampling points N−1, N and N+1;

b) associating a profile type with said threshold function;

c) receiving a parameter value for verification against said threshold function, said parameter value being associated with a discrete time P;

d) combining at least some of said sequence of reference values with said profile type to provide an approximation of said threshold function for a region of said threshold function between said reference values; and

e) verifying said parameter value against said approximation of said threshold function.

10. A computer-readable medium according to claim 9 , wherein said sequence of reference values comprises three reference values but in step d) only the two reference values associated with sampling points N closest to said time P are combined with said profile type.

11. A computer-readable medium according to claim 9 , wherein said method comprises a further step of comparing said time P to said sampling points and if N<=P<=N+1, then replacing said reference value N−1 with a new reference value N+2 for use with a subsequently received parameter value.

12. A computer-readable medium according to claim 9 , wherein said method comprises a further step of comparing said time P to said sampling points and if P<N+1, then replacing said sequence with a further sequence of reference values N′− 1 , N′ and N′+1 for use in step e).