A pilot sequence generator arranged to generate pilot sequences for an uplink and/or for a downlink transmission, wherein the pilot sequence generator is configured to: - generate a pilot sequence set comprising M+1 pilot sequence sub-sets, wherein M is a positive integer that is equal to or greater than one, wherein the pilot sequence generator is configured to generate the pilot sequence set comprising the M+1 pilot sequence sub-sets by executing the following: - dividing an initial pilot sequence set, comprising orthogonal pilot sequences, in a non-processed pilot sequence sub-set and M to-be-processed pilot sequence sub-sets; and - generating M processed non-orthogonal pilot sequence sub-sets, wherein a processing unit is configured, for each to-be-processed pilot sequence sub-set of the M to-be-processed pilot sequence sub-sets, to generate a processed non-orthogonal pilot sequence sub-set by multiplying a to-be-processed pilot sequence sub-set matrix, comprising pilot sequences of the respective to-be-processed pilot sequence sub-set as columns, with a complex matrix, wherein columns of matrix resulting from the multiplication represent the respective processed non-orthogonal pilot sequence sub-set; the M+1 pilot sequence sub-sets comprise the non-processed pilot sequence sub-set and the M processed non-orthogonal pilot sequence sub-sets, wherein the complex matrix is a N non-orth × K non-orth matrix, N non-orth < K non-orth, and columns of the complex matrix are any K non-orth points on a N non-orth -dimensional complex sphere of radius 1 with a minimal pairwise angle that is as large as possible, wherein the pilot sequences of the respective non-orthogonal pilot sequence sub-set are not orthogonal to each other, wherein each non-orthogonal pilot sequence sub-set of the M non-orthogonal pilot sequence sub-sets is orthogonal to each other non-orthogonal pilot sequence sub-set of the M non-orthogonal pilot sequence sub-sets; - assign the M+1 pilot sequence sub-sets to M+1 groups of user communication devices, wherein each pilot sequence sub-set of the M+1 pilot sequence sub-sets is assigned to one group of user communication devices, wherein each group of user communication devices comprises one or more user communication devices, and wherein, by the assignment, the one or more user communication devices of each group of user communication devices of the M+1 groups of user communication devices are configured to use, for the uplink and/or for the downlink transmission, pilot sequences of the pilot sequence sub-set assigned to the respective group of user communication devices. - generate a pilot sequence set comprising M+1 pilot sequence sub-sets, wherein M is a positive integer that is equal to or greater than one, wherein the pilot sequence generator is configured to generate the pilot sequence set comprising the M+1 pilot sequence sub-sets by executing the following: - dividing an initial pilot sequence set, comprising orthogonal pilot sequences, in a non-processed pilot sequence sub-set and M to-be-processed pilot sequence sub-sets; and - generating M processed non-orthogonal pilot sequence sub-sets, wherein a processing unit is configured, for each to-be-processed pilot sequence sub-set of the M to-be-processed pilot sequence sub-sets, to generate a processed non-orthogonal pilot sequence sub-set by multiplying a to-be-processed pilot sequence sub-set matrix, comprising pilot sequences of the respective to-be-processed pilot sequence sub-set as columns, with a complex matrix, wherein columns of matrix resulting from the multiplication represent the respective processed non-orthogonal pilot sequence sub-set; the M+1 pilot sequence sub-sets comprise the non-processed pilot sequence sub-set and the M processed non-orthogonal pilot sequence sub-sets, wherein the complex matrix is a N non-orth × K non-orth matrix, N non-orth < K non-orth, and columns of the complex matrix are any K non-orth points on a N non-orth -dimensional complex sphere of radius 1 with a minimal pairwise angle that is as large as possible, wherein the pilot sequences of the respective non-orthogonal pilot sequence sub-set are not orthogonal to each other, wherein each non-orthogonal pilot sequence sub-set of the M non-orthogonal pilot sequence sub-sets is orthogonal to each other non-orthogonal pilot sequence sub-set of the M non-orthogonal pilot sequence sub-sets; - assign the M+1 pilot sequence sub-sets to M+1 groups of user communication devices, wherein each pilot sequence sub-set of the M+1 pilot sequence sub-sets is assigned to one group of user communication devices, wherein each group of user communication devices comprises one or more user communication devices, and wherein, by the assignment, the one or more user communication devices of each group of user communication devices of the M+1 groups of user communication devices are configured to use, for the uplink and/or for the downlink transmission, pilot sequences of the pilot sequence sub-set assigned to the respective group of user communication devices.