A base station is provided. The base station comprises a downlink transmit path comprising circuitry configured to transmit a plurality of reference signals in two or more subframes. Each subframe comprises one or more resource blocks. Each resource block comprises S OFDM symbols. Each of the S OFDM symbols comprises N subcarriers, and each subcarrier of each OFDM symbol comprises a resource element. The base station further comprises a reference signal allocator configured to allocate a first group of the plurality of reference signals to selected resource elements of a first subframe according to a reference signal pattern. The first group of the plurality of reference signals is for a first group of antenna ports. The reference signal allocator also configured to allocate a second group of the plurality of reference signals to selected resource elements of a second subframe according to the same reference signal pattern. The second group of the plurality of reference signals is for a second group of antenna ports different from the first group of antenna ports.