A decoder for decoding a signal received through a transmission channel in a communication system, said transmission channel being represented by an upper triangular matrix, said signal comprising a vector of information symbols, wherein the decoder comprises: - a processing unit configured to determine at least two candidate sets of division parameters and to perform a division of said vector of information symbols into a set of sub-vectors in association with each candidate set of division parameters and a division of said upper triangular matrix into at least two sub-matrices, a pair of sub-vectors comprised in said set of sub-vectors being associated with a rectangular sub-matrix from said at least two sub-matrices and a division metric, said division metric being derived from the components of said rectangular sub-matrix; - a selection unit configured to select one of said candidate sets of division parameters according to a selection criterion depending on said division metric; and - a decoding unit configured to determine at least one estimate of each sub-vector associated with said selected set of division parameters by applying a symbol estimation algorithm, wherein the decoder is configured to determine at least one estimate of the vector of information symbols from said at least one estimate of each sub-vector of information symbols, wherein said division metric is a ratio between: - the number of the components comprised in the rectangular sub-matrix that have an absolute value lower than or equal to a reference value, and - the total number of components comprised in the rectangular sub-matrix, said reference value being a positive real number higher than or equal to zero, wherein said selection criterion comprises: - determining, for each candidate set of division parameters, a reference division metric corresponding to the lowest division metric value among the division metrics associated with the pairs of sub-vectors of the set of sub-vectors associated with the candidate set of division parameters, - determining, among the candidate sets of division parameters, the candidate set of division parameters that has the highest value of the reference division metric. - a processing unit configured to determine at least two candidate sets of division parameters and to perform a division of said vector of information symbols into a set of sub-vectors in association with each candidate set of division parameters and a division of said upper triangular matrix into at least two sub-matrices, a pair of sub-vectors comprised in said set of sub-vectors being associated with a rectangular sub-matrix from said at least two sub-matrices and a division metric, said division metric being derived from the components of said rectangular sub-matrix; - a selection unit configured to select one of said candidate sets of division parameters according to a selection criterion depending on said division metric; and - a decoding unit configured to determine at least one estimate of each sub-vector associated with said selected set of division parameters by applying a symbol estimation algorithm, wherein the decoder is configured to determine at least one estimate of the vector of information symbols from said at least one estimate of each sub-vector of information symbols, wherein said division metric is a ratio between: - the number of the components comprised in the rectangular sub-matrix that have an absolute value lower than or equal to a reference value, and - the total number of components comprised in the rectangular sub-matrix, - the number of the components comprised in the rectangular sub-matrix that have an absolute value lower than or equal to a reference value, and - the total number of components comprised in the rectangular sub-matrix, said reference value being a positive real number higher than or equal to zero, wherein said selection criterion comprises: - determining, for each candidate set of division parameters, a reference division metric corresponding to the lowest division metric value among the division metrics associated with the pairs of sub-vectors of the set of sub-vectors associated with the candidate set of division parameters, - determining, among the candidate sets of division parameters, the candidate set of division parameters that has the highest value of the reference division metric. - determining, for each candidate set of division parameters, a reference division metric corresponding to the lowest division metric value among the division metrics associated with the pairs of sub-vectors of the set of sub-vectors associated with the candidate set of division parameters, - determining, among the candidate sets of division parameters, the candidate set of division parameters that has the highest value of the reference division metric.