orthogonality in cyclic shift and orthogonal cover code selection for dmrs in mimo is improved by new n dmrs to n dmrs mapping patterns . values in the mapping tables are arranged in sets , with minimum cs separation between the values in each set . additionally , the semi - static n dmrs is independently configurable for each ul component carrier in the case of cross - cc scheduling in carrier aggregation , and the phich allocation formula that defines the allocation of the phich process relative to the k th codeword on the c th ul cc is a function of both the cs index n dmrs , k , c that is dynamically assigned to a certain layer of the considered cw and the semi - static cs offset n dmrs , c for the c th cc .