Patent ID: 8630360

Claim:
A method of transmitting a reference signal by a user equipment (UE) in a wireless communication system, the method comprising: generating, by the UE, an uplink reference signal in a subframe, the uplink reference signal used by a base station to demodulate a hybrid automatic repeat request (HARQ) ACK/NACK signal of the UE, the subframe comprising a plurality of orthogonal frequency division multiplexing (OFDM) symbols in time domain and a plurality of subcarriers in frequency domain; and transmitting, by the UE to the base station, the uplink reference signal only in a first set of the OFDM symbols of the subframe; and transmitting, by the UE to the base station, the HARQ ACK/NACK signal only in a second set of the OFDM symbols of the subframe different from the first set of the OFDM symbols of the subframe, wherein the step of generating the uplink reference signal includes: determining a sequence group from a plurality of frequency sequence groups based on a cell specific hopping parameter; determining a basic frequency spreading sequence based on the determined sequence group; generating a frequency spreading sequence by cyclically shifting the determined basic frequency spreading sequence; and generating the uplink reference signal by spreading the frequency spreading sequence only over the first set of the OFDM symbols with an orthogonal spreading code.