A decoder configured to decode a signal received through a transmission channel represented by a channel matrix using a search sphere radius, the decoder comprising a radius determination device for determining said search sphere radius from a preliminary radius, wherein the radius determination device is configured to determine the search sphere radius according to an iterative process by updating a current radius during a number of iterations until a termination condition is satisfied, wherein the radius determination device is configured to: i. apply a machine learning algorithm to input data derived from said received signal, said channel matrix and a current radius, said input data derived from said received signal being a vector of information symbols, the current radius being initially set to the preliminary radius, which provides a current predicted number of lattice points associated with said current radius; ii. compare said current predicted number of lattice points to a given threshold; iii. update said current radius if said current predicted number of lattice points is strictly higher than said given threshold, said current radius being updated by applying a linear function to said current radius; steps i to iii being iterated until the termination condition is satisfied, said termination condition being related to the current predicted number, the radius determination device being configured to set the search sphere radius to the current radius in response to the termination condition being satisfied, the termination condition being satisfied if the current predicted number of lattice points is smaller than or equal to said given threshold, wherein said linear function applied to update the current sphere radius provides the current sphere radius r s i at an iteration of index i as a function of the sphere radius r s i − 1 obtained at the previous iteration of index (i-1), wherein the decoder further comprises a symbol estimation unit configured to determine at least one estimate of a vector of information symbols carried by the received signal by applying a sphere search-based estimation algorithm that determines said at least one estimate of vector of information symbols from lattice points found inside a spherical region centered at a point representing said received signal and defined by said search sphere radius. i. apply a machine learning algorithm to input data derived from said received signal, said channel matrix and a current radius, said input data derived from said received signal being a vector of information symbols, the current radius being initially set to the preliminary radius, which provides a current predicted number of lattice points associated with said current radius; ii. compare said current predicted number of lattice points to a given threshold; iii. update said current radius if said current predicted number of lattice points is strictly higher than said given threshold, said current radius being updated by applying a linear function to said current radius; steps i to iii being iterated until the termination condition is satisfied, said termination condition being related to the current predicted number, the radius determination device being configured to set the search sphere radius to the current radius in response to the termination condition being satisfied, the termination condition being satisfied if the current predicted number of lattice points is smaller than or equal to said given threshold, wherein said linear function applied to update the current sphere radius provides the current sphere radius r s i at an iteration of index i as a function of the sphere radius r s i − 1 obtained at the previous iteration of index (i-1), wherein the decoder further comprises a symbol estimation unit configured to determine at least one estimate of a vector of information symbols carried by the received signal by applying a sphere search-based estimation algorithm that determines said at least one estimate of vector of information symbols from lattice points found inside a spherical region centered at a point representing said received signal and defined by said search sphere radius. steps i to iii being iterated until the termination condition is satisfied, said termination condition being related to the current predicted number, the radius determination device being configured to set the search sphere radius to the current radius in response to the termination condition being satisfied, the termination condition being satisfied if the current predicted number of lattice points is smaller than or equal to said given threshold, wherein said linear function applied to update the current sphere radius provides the current sphere radius r s i at an iteration of index i as a function of the sphere radius r s i − 1 obtained at the previous iteration of index (i-1), wherein the decoder further comprises a symbol estimation unit configured to determine at least one estimate of a vector of information symbols carried by the received signal by applying a sphere search-based estimation algorithm that determines said at least one estimate of vector of information symbols from lattice points found inside a spherical region centered at a point representing said received signal and defined by said search sphere radius.