1. A method, comprising: receiving a Cyclic Shift (CS) parameter from a Base Station (BS); and transmitting, to the BS, reference signals for N layers, the reference signals being generated based on the CS parameter and an Orthogonal Cover Code (OCC), N being an integer, wherein if the CS parameter comprises one of 000, 001, 010 and 111, OCCs of a first layer and a second layer are identical and OCCs of a third layer and a fourth layer are identical while the OCC of the third layer is different from the OCC of the first layer, and wherein if the CS parameter comprises one of 101, 011, 100 and 110, an OCC is identically allocated to all of the N layers.