A decoder for decoding a signal received through a transmission channel in a communication system, said signal comprising a vector of information symbols, said transmission channel being represented by a channel matrix, wherein the decoder comprises: - an initial radius determination unit configured to determine an initial radius depending on a noise variance and/or a predefined number of target lattice points; - a symbol estimation unit configured to search a lattice point inside a current spherical region defined by a current radius centered at a point representing said signal, each lattice point found in said current spherical region being stored in association with a metric determined from the Euclidean distance between said signal and said lattice point, said current radius being initially set to said initial radius, said symbol estimation unit being configured to determine a second radius and iteratively update said current radius by applying a linear function having a slope parameter strictly inferior to one, to: • the metric associated with the found lattice point, if a lattice point is found in said current spherical region and if said second radius is smaller than a value, said value being determined by applying said linear function to said metric, or • the sum of the metric associated with the found lattice point and said second radius if said second radius is larger than or equal to said value determined by applying the linear function to said metric, or • the sum of the metric associated with the last found lattice point and the value of said second radius, if the current radius is larger than said second radius and no lattice point is found in the current spherical region, the second radius being updated to said current radius; the symbol estimation unit being further configured to terminate the updating of the current radius when no lattice point is found in the current spherical region and the current radius is smaller than or equal to the second radius; the decoder is configured to determine at least one estimate of said vector of information symbols from at least one of the lattice points found by the symbol estimation unit. - an initial radius determination unit configured to determine an initial radius depending on a noise variance and/or a predefined number of target lattice points; - a symbol estimation unit configured to search a lattice point inside a current spherical region defined by a current radius centered at a point representing said signal, each lattice point found in said current spherical region being stored in association with a metric determined from the Euclidean distance between said signal and said lattice point, said current radius being initially set to said initial radius, said symbol estimation unit being configured to determine a second radius and iteratively update said current radius by applying a linear function having a slope parameter strictly inferior to one, to: • the metric associated with the found lattice point, if a lattice point is found in said current spherical region and if said second radius is smaller than a value, said value being determined by applying said linear function to said metric, or • the sum of the metric associated with the found lattice point and said second radius if said second radius is larger than or equal to said value determined by applying the linear function to said metric, or • the sum of the metric associated with the last found lattice point and the value of said second radius, if the current radius is larger than said second radius and no lattice point is found in the current spherical region, the second radius being updated to said current radius; the symbol estimation unit being further configured to terminate the updating of the current radius when no lattice point is found in the current spherical region and the current radius is smaller than or equal to the second radius; the decoder is configured to determine at least one estimate of said vector of information symbols from at least one of the lattice points found by the symbol estimation unit. • the metric associated with the found lattice point, if a lattice point is found in said current spherical region and if said second radius is smaller than a value, said value being determined by applying said linear function to said metric, or • the sum of the metric associated with the found lattice point and said second radius if said second radius is larger than or equal to said value determined by applying the linear function to said metric, or • the sum of the metric associated with the last found lattice point and the value of said second radius, if the current radius is larger than said second radius and no lattice point is found in the current spherical region, the second radius being updated to said current radius;