Viterbi decoder with reduced number of data move operations
First Claim
1. In a Viterbi decoder for determining a maximum likelihood path from a plurality of surviving paths through a trellis, said trellis having a plurality of states repeated for each one of a plurality of time units, with the number of said surviving paths being equal to the number of states in said trellis, said Viterbi decoder having means for storing and retrieving said plurality of surviving paths, the improvement in said means for storing and retrieving said plurality of surviving paths comprising:
- memory means having a plurality of groups of addressable locations, the number of said groups being equal to the number of said states in said trellis and each one of said groups being associated with a unique one of said states;
said memory means further having each one of said addressable locations of each said group associated with a unique one of said plurality of time units;
means for storing in each said addressable location, associated with one of said states of one of said surviving paths, the previous state of said one of said surviving paths; and
means for retrieval of said maximum likelihood path by repeatedly reading one of said addressable locations associated with said maximum likelihood path to obtain said previous state of said maximum likelihood path and thereby to determine for the previous time unit which of said addressable locations is to be read.
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Accused Products
Abstract
Disclosed is a modem including a transmitter having a convolutional encoder for transforming each time unit digital data into an expanded bit sequence having symbol-selecting bits and subset-selecting bits, the transmitter further providing modulation of a carrier signal and a receiver wherein a Viterbi decoder determines the maximum likelihood path through a trellis from a plurality of surviving paths using a wraparound memory wherein in each addressable location indexed to a current state of a surviving path there is stored a previous state of that surviving path.
76 Citations
22 Claims
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1. In a Viterbi decoder for determining a maximum likelihood path from a plurality of surviving paths through a trellis, said trellis having a plurality of states repeated for each one of a plurality of time units, with the number of said surviving paths being equal to the number of states in said trellis, said Viterbi decoder having means for storing and retrieving said plurality of surviving paths, the improvement in said means for storing and retrieving said plurality of surviving paths comprising:
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memory means having a plurality of groups of addressable locations, the number of said groups being equal to the number of said states in said trellis and each one of said groups being associated with a unique one of said states; said memory means further having each one of said addressable locations of each said group associated with a unique one of said plurality of time units; means for storing in each said addressable location, associated with one of said states of one of said surviving paths, the previous state of said one of said surviving paths; and means for retrieval of said maximum likelihood path by repeatedly reading one of said addressable locations associated with said maximum likelihood path to obtain said previous state of said maximum likelihood path and thereby to determine for the previous time unit which of said addressable locations is to be read. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a Viterbi decoder for determining a minimum cost path from a plurality of surviving paths through a trellis which has a plurality of states repeated in each of a plurality of time units, the improvement comprising:
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memory means having an addressable location indexed to each combination of one of said time units with one of said states; means for storing in each said addressable location, indexed to a current said state of one of said surviving paths, a previous said state of said one of said surviving paths; and means for retrieving said minimum cost path by repeatedly reading one of said addressable locations associated with one of said current states of said minimum cost path to provide said previous state of said minimum cost path which in turn becomes a new said current state of said minimum cost path for a subsequent said reading. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. In a method for determining a minimum cost path from a plurality of surviving paths through a trellis which has a plurality of states repeated in each of a plurality of time units, the improvement comprising the steps of:
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indexing an addressable location in a memory to each unique combination of one of said time units with one of said states; storing in each said addressable location, indexed to one of said states of one of said surviving paths, a previous said state of said one of said surviving paths; and starting with said addressable locations indexed to the newest said time unit, retrieving said minimum cost path by repeatedly reading one of said addressable locations associated with one of said states of said minimum cost path to provide said previous state of said minimum cost path which in turn defines which one of said addressable locations indexed to the next prior time unit is to be read next. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification