Demodulator of base station in orthogonal frequency division multiple access

1. A base station demodulator for demodulating channel quality information (CQI) or an automatic repeat request (ARQ) response signal transmitted from a subscriber station to a base station, the base station demodulator comprising:

a vector index demodulator for demodulating quadrature phase shift keying (QPSK) modulation signals transmitted by using m subcarriers in a tile by multiplying the QPSK modulation signals, in parallel, by m conjugate complexes corresponding to the m subcarriers, and determining the greatest value of the demodulation results as a vector index when the CQI tiles or the ARQ acknowledgement/negative-acknowledgement (ACK/NACK) channel tiles are sequentially inputted; and

a channel value detector for inputting n vector indexes demodulated by the vector index demodulator to a first shift register, inputting n subsequent vector indexes to a second shift register, performing the above vector index input to the first and second shift registers m-times, and detecting a channel value for the CQI or the ARQ ACK/NACK;

wherein m and n are integers.

2. The base station demodulator of claim 1 , wherein the vector index demodulator comprises:

m multiplexers for multiplying the QPSK modulation signals transmitted by using the m subcarriers in a tile by the conjugate complexes corresponding to them subcarriers in parallel when the CQI tiles or the ARQ ACK/NACK channel tiles are sequentially inputted;

m adders for respectively adding values obtained by multiplying the m QPSK modulation signals by the m conjugate complexes;

m signal amplitude measuring units for measuring amplitude of the m QPSK modulation signals; and

m determining units for determining the greatest value of the demodulation results as the corresponding vector index according to values measured by the m signal amplitude measuring units.

3. The base station demodulator of claim 2 , wherein the conjugate complexes are multiplied without the multiplier and the adder when the conjugate complexes are multiplied by

exp

⁡

(

j

·

π

4

)

.

4. The base station demodulator of claim 1 or claim 2 , wherein m includes 8.

5. The base station demodulator of claim 1 , wherein the QPSK modulation signals respectively become 1 when the QPSK modulation signals are respectively multiplied by the conjugate complexes of the QPSK modulation signals, and the QPSK modulation signals respectively become 0 when the QPSK modulation signals are multiplied by the other conjugate complexes.

6. The base station demodulator of claim 1 , wherein the channel value detector comprises:

a first shift register for receiving the n vector indexes demodulated by the vector index demodulator;

a second shift register for receiving the subsequent n vector indexes demodulated by the vector index demodulator; and

a channel value determining unit for performing the vector index input to the first and second shift registers m-times, and determining a channel value for the CQI or the ARQ ACK/NACK.

7. The base station demodulator of claim 6 , wherein the channel value determining unit determines a value having the least difference between an output value of the second shift register and a predetermined value as the channel value for the CQI or the ARQ ACK/NACK after comparing the output value of the second shift register with the predetermined value.

8. The base station demodulator of claim 7 , wherein the CQI is determined to be one of the 32 levels according to the determination of the channel value determining unit.

9. The base station demodulator of claim 7 , wherein the ARQ signal is determined to be one of ACK and NACK according to the determination of the channel value determining unit.

10. The base station demodulator of claim 1 or claim 6 , wherein n includes 6.