A base station demodulator according to the exemplary embodiment of the present invention includes a vector index demodulator, and a channel value detector. The vector index demodulator demodulates CQI or ARQ ACK/NACK channels by multiplying QPSK modulation signals transmitted as m subcarriers in a tile by m conjugate complexes corresponding to the m subcarriers, and determines the greatest value of the demodulation results as a vector index. The channel value detector inputs n vector indexes demodulated by the vector index demodulator to a first shift register, inputs n subsequent vector indexes to a second shift register, and detects a channel value for the CQI or the ARQ ACK/NACK by repeating the above vector index input to the first and second shift registers m-times.