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US 7,117,427 B2Granted
Reduced complexity decoding for trellis coded modulation
AssigneeTexas Instruments Incorporated
InventorsLior Ophir, Itay Lusky
Life of this patent
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Abstract
The present application describes a method of implementing a Viterbi algorithm (VA) for trellis coded modulation (TCM) decoding in communication equipment. According to an embodiment, a branch metric is calculated by adding the absolute value of the real and imaginary parts of a complex vector resulting from the subtraction of a received symbol and a constellation point that is the closest to the symbol in each subset.
Claims16
A method of TCM decoding, the method comprising the steps of:
- a) receiving a soft symbol;
- b) choosing a constellation point closest to the received soft symbol for each TCM subset;
- c) calculating the metric of each branch based on the distance of the chosen point from the received symbol, wherein the distance is Euclidean distance;
- d) calculating new state metrics for each trellis state as the minimum of the sums of all possible previous states and appropriate branch that lead to a new state;
- e) selecting the state with the smallest metric;
- and
- f) tracing back from the state with the smallest metric, to determine the state and appropriate transmitted symbol(s) having a delay based on the traceback length,
- wherein steps b and c together choose between parallel branches between states in the trellis, and assign branch metrics to each branch and each branch metric is calculated by adding the absolute value of the real and imaginary parts of the complex vector resulting from the subtraction of the received symbol and the closest symbol in each subset to implement simplified metric VA decoding.
5 more elements
A method of implementing a VA on a DSP, the method comprising the steps of:
- a) receiving a soft symbol;
- b) for each TCM subset, choosing the constellation point closest to the received symbol;
- c) calculating the distance of this selected point from the received symbol, via choosing between parallel branches between states in the trellis, and assigning branch metrics to each branch;
- d) Examining each trellis state and calculating new state metrics as the minimum of the sums of all possible previous states and appropriate branch that lead to this state;
- e) Selecting the state with the smallest metric, and tracing back from this state to decide in the state and appropriate transmitted symbol(s) with delay based on the traceback length;
- and
- f) Repeating steps a–e,
- wherein steps b and c together choose between parallel branches between states in the trellis, and assign branch metrics to each branch and each branch metric is calculated by adding the absolute value of the real and imaginary parts of the complex vector resulting from the subtraction of the received symbol and the closest symbol in each subset to implement simplified metric VA decoding.
5 more elements
Dependencies are inferred from the claim text.