A base station is provided. The base station comprises a downlink transmit path comprising circuitry configured to transmit a plurality of reference signals in one or more subframes. Each subframe comprises one or more resource blocks. Each resource block comprises S Orthogonal Frequency Division Multiplexing (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 the plurality of reference signals to selected resource elements of a resource block, and circularly shift the plurality of reference signals in a time domain of the resource block by an hshift value that is based at least partly upon a cell_ID of the base station.