A base station includes a reference signal allocator that allocates a first layer of dedicated reference signals and a second layer of reference signals to the same resource elements in a first resource block. The reference signals are allocated to two adjacent resource elements corresponding to a first OFDM symbol and a second OFDM symbol on a first, second, and third subcarriers of the first resource block. The base station also includes a reference signal multiplexer that multiplexes the first layer with the second layer. A first cover code W1 is applied to the first layer. A second cover code W2, different from the first cover code, is applied to the second layer in a first and third subcarriers, and a variation of the second cover code W2′ is applied to the second layer in a second subcarrier.