WIRELESS COMMUNICATIONS APPARATUS
First Claim
1. A method for determining soft estimates of transmitted bit values from a received signal in a lattice-reduction-aided receiver based wireless communications system, the method comprising:
- obtaining an estimate of a channel response;
applying lattice reduction to said channel response and equalization of said received signal in accordance with a reduced basis channel; and
determining probabilities of transmitted bits having particular values, wherein the determining step includesdetermining an initial candidate vector in the reduced basis; and
determining Log Likelihood Ratios (LLR) of each transmitted bit, said LLRs being based on Euclidian distances of candidate vectors from said channel response, wherein the step of determining LLRs includesdetermining a Euclidian distance between said initial candidate vector and said channel response;
determining a reduced basis matrix corresponding to a reduced basis description of the lattice, wherein said reduced basis matrix comprises substantially orthogonal basis vectors;
determining column norms for said basis vectors; and
determining distances for further determined candidate vectors, each distance being determined as a sum of (1) said calculated distance for said initial candidate symbol vector;
(2) a product of a selected one of the predetermined column norms and an integer multiple of the minimum inter-candidate distance; and
(3) either a positive or a negative multiple of 2 of a scalar product of said selected predetermined column with a vector difference between the channel response vector and the initial candidate vector.
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Accused Products
Abstract
In a lattice-reduction-aided receiver based wireless communications system, soft estimates of transmitted bit values are determined from a received signal by applying lattice reduction to the channel estimate and equalising the received signal in accordance with the reduced basis channel, and determining probabilities of transmitted bits having particular values. The method includes selecting an initial candidate vector in the reduced basis and determining further candidate vectors in the reduced basis dependently of the initial candidate vector, determining a corresponding transmitted symbol vector for each candidate vector and, on the basis of the received signal determining the probability of each transmitted bit value having been transmitted and log-likelihood ratios of transmitted bits. Determination of the log-likelihood ratio includes determining a first Euclidean distance corresponding to the initial symbol vector and a modified channel state matrix corresponding to the wireless communication system and then iteratively using the determined information to determine further Euclidean distances of further symbol vectors.
17 Citations
13 Claims
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1. A method for determining soft estimates of transmitted bit values from a received signal in a lattice-reduction-aided receiver based wireless communications system, the method comprising:
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obtaining an estimate of a channel response; applying lattice reduction to said channel response and equalization of said received signal in accordance with a reduced basis channel; and determining probabilities of transmitted bits having particular values, wherein the determining step includes determining an initial candidate vector in the reduced basis; and determining Log Likelihood Ratios (LLR) of each transmitted bit, said LLRs being based on Euclidian distances of candidate vectors from said channel response, wherein the step of determining LLRs includes determining a Euclidian distance between said initial candidate vector and said channel response; determining a reduced basis matrix corresponding to a reduced basis description of the lattice, wherein said reduced basis matrix comprises substantially orthogonal basis vectors; determining column norms for said basis vectors; and determining distances for further determined candidate vectors, each distance being determined as a sum of (1) said calculated distance for said initial candidate symbol vector;
(2) a product of a selected one of the predetermined column norms and an integer multiple of the minimum inter-candidate distance; and
(3) either a positive or a negative multiple of 2 of a scalar product of said selected predetermined column with a vector difference between the channel response vector and the initial candidate vector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 13)
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9. An apparatus for determining soft estimates of transmitted bit values from a received signal in a lattice-reduction-aided receiver based wireless communications system, the apparatus comprising:
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means for obtaining an estimate of a channel response; means for applying lattice reduction to said channel response and equalization of said received signal in accordance with a reduced basis channel; and means for determining probabilities of transmitted bits having particular values, said means for determining probabilities including means for determining an initial candidate vector in the reduced basis; and means for determining Log Likelihood Ratios (LLR) of each transmitted bit, said LLRs being based on Euclidian distances of candidate vectors from said channel response, wherein said means for determining LLRs includes means for determining a Euclidian distance between said initial candidate vector and said channel response; means for determining a reduced basis matrix corresponding to a reduced basis description of the lattice, wherein said reduced basis matrix comprises substantially orthogonal basis vectors; means for determining column norms for said basis vectors; and means for determining distances for further determined candidate vectors, said means for determining distances being configured to determine each distance as a sum of (1) said calculated distance for said initial candidate symbol vector;
(2) a product of a selected one of the predetermined column norms and an integer multiple of the minimum inter-candidate distance; and
(3) either a positive or a negative multiple of 2 of a scalar product of said selected predetermined column with a vector difference between the channel response vector and the initial candidate vector. - View Dependent Claims (10, 11, 12)
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Specification