Fast space-time decoding using soft demapping with table look-up
First Claim
1. A method comprising:
- a) providing a symbol vector table comprising symbol vectors corresponding to potential combinations of transmitted symbols;
b) determining first Euclidean distances between a received signal and a plurality of the symbol vectors in light of corresponding channel responses;
c) selecting a first smallest distance from the first Euclidean distances as a hard decision;
d) determining a bit vector corresponding to the first smallest distance; and
e) for each bit in the bit vector;
i) selecting second Euclidean distances corresponding to a competing bit from the first Euclidean distances; and
ii) selecting a competing smallest distance from the second Euclidean distances as a soft demapping value.
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Abstract
From potential symbol combinations transmitted from a transmitter, Euclidean distances between the received signals and the symbol vectors are determined in light of the corresponding channel responses and stored in a Euclidean distance table, from which the smallest Euclidean distance is selected as a hard decision. The hard decision is used to find a bit vector corresponding to the estimated symbol vector associated with the hard decision. For each bit in the bit vector, a reduced Euclidean distance table is created to include only Euclidean distances associated with a competing bit associated with the hard decision. The minimum Euclidean distance from each reduced Euclidean distance table becomes a soft demapping decision for a corresponding bit. Log likelihood ratios for each bit are determined by the difference between the hard decision and respective soft demapping decisions. The differences are provided to a channel decoder to recover the originally transmitted bits.
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Citations
36 Claims
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1. A method comprising:
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a) providing a symbol vector table comprising symbol vectors corresponding to potential combinations of transmitted symbols;
b) determining first Euclidean distances between a received signal and a plurality of the symbol vectors in light of corresponding channel responses;
c) selecting a first smallest distance from the first Euclidean distances as a hard decision;
d) determining a bit vector corresponding to the first smallest distance; and
e) for each bit in the bit vector;
i) selecting second Euclidean distances corresponding to a competing bit from the first Euclidean distances; and
ii) selecting a competing smallest distance from the second Euclidean distances as a soft demapping value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A system for receiving signals comprising decoder circuitry adapted to:
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a) provide a symbol vector table comprising symbol vectors corresponding to potential combinations of transmitted symbols;
b) determine first Euclidean distances between a received signal and a plurality of the symbol vectors in light of corresponding channel responses;
c) select a first smallest distance from the first Euclidean distances as a hard decision;
d) determine a bit vector corresponding to the first smallest distance; and
e) for each bit in the bit vector;
i) select second Euclidean distances corresponding to a competing bit from the first Euclidean distances; and
ii) select a competing smallest distance from the second Euclidean distances as a soft demapping value. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A method comprising:
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a) determining first terms associated with differences between a received signal and a plurality of symbol vectors in light of corresponding channel responses, the symbol vectors corresponding to potential combinations of transmitted symbols;
b) selecting a first smallest term from the first terms as a hard decision;
c) determining bits corresponding to the first smallest term; and
d) for each bit of the bits;
i. selecting second terms corresponding to a competing bit from the first terms; and
ii. selecting a competing smallest term from the second terms as a soft demapping value. - View Dependent Claims (32, 33, 34, 35, 36)
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Specification