Method for determining a most likely sequence of states
First Claim
1. A method for determining the most likely state sequence ending in a state s at a time t corresponding to a sequence of observations from an initial time interval to time t, comprising the steps of:
- a. receiving the sequence of observations;
b. comparing the observations to known parameters for N number of states;
c. determining a best state sequence for each of the N number of states at time t-1 based on this comparison;
d. identifying a first number of the best state sequences at t-1, the first number being less than N, one of which sequences will provide an optimal state sequence to s at time t;
e. processing only the first number of the best state sequences; and
f. selecting an optimal state sequence from the processed best state sequences; and
wherein the step of determining comprises determining the best state sequences by iteratively calculating the most likely state sequences for each of the N states from the initial time to time t-1.
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Abstract
The number of calculations to determine the most likely path is reduced by eliminating a number of paths that are impossible to provide an optimal result. How to eliminate these non-optimal paths, thus greatly reducing the number of calculations performed by a signal processor. The determination of the probability score of the best path to state s at time t may be found as follows. First, transition probabilities to state s are sorted in order of descending probability. Second, the k highest probability scores at time t-1 are identified. Third, the highest transition probability associated with the k highest probability scores at t-1 is identified and designated maxrank. Fourth, the k highest probability scores at t-1 are multiplied with their associated transition probabilities with the highest product being designated maxvalue. Fifth, all transition probabilities higher than maxrank are multiplied with their associated probability scores at t-1. If the product of one of these multiplications is greater than the current maxvalue, this product becomes the new maxvalue. The final maxvalue is multiplied by an observation probability to determine a most likely path sequence to state s at time-1. K is chosen to be √N, where N is the total number of possible states.
10 Citations
9 Claims
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1. A method for determining the most likely state sequence ending in a state s at a time t corresponding to a sequence of observations from an initial time interval to time t, comprising the steps of:
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a. receiving the sequence of observations; b. comparing the observations to known parameters for N number of states; c. determining a best state sequence for each of the N number of states at time t-1 based on this comparison; d. identifying a first number of the best state sequences at t-1, the first number being less than N, one of which sequences will provide an optimal state sequence to s at time t; e. processing only the first number of the best state sequences; and f. selecting an optimal state sequence from the processed best state sequences; and
wherein the step of determining comprises determining the best state sequences by iteratively calculating the most likely state sequences for each of the N states from the initial time to time t-1. - View Dependent Claims (2, 3, 4, 5)
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6. A method for determining a most likely state sequence at a time t for a state s in a system having N possible states, comprising the steps of:
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a. receiving a number of observations from an initial time to time t; b. sorting a plurality of transition probabilities to state s associated with the N states in order of descending probability; c. identifying k highest state probability scores among the N states at a time t - 1; d. designating as maxrank a highest transition probability associated with the k highest state probability scores at time t-1; e. multiplying the k highest state probability scores at time t-1 with their associated transition probabilities; f. designating as a current maxvalue a highest product of this multiplication; g. multiplying all transition probabilities higher than maxrank with their associated state probability scores; h. replacing the current maxvalue with a new maxvalue if a product of one of the multiplications of a transition probability higher than maxrank is greater than the current maxvalue. - View Dependent Claims (7, 8, 9)
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Specification