An method for, in a cellular telecommunication system, generating reference sequence matrices and for mapping elements of said reference sequence matrices to reference signal positions having predetermined locations in two-dimensional multi-carrier time-frequency symbol spaces is provided. According to the method, a matrix SN of dimension N×N having N orthogonal rows or columns and orthogonal parts of rows or columns, respectively, N being a positive integer >3, is generated. N reference sequence matrices OS(k), k=0, . . . , N−1, are then generated by forming rows or columns of the kth reference sequence matrix OS(k) based on at least part of the (k+1)th row or column, respectively, of said orthogonal matrix SN. Further, in a cell, within a given time period, mapping elements of one of said N reference sequence matrices OS(k) to reference signal positions having predetermined locations in two-dimensional multi-carrier time-frequency symbol spaces.