function rec_symbol = fft_cp_rx_blk(ofdm_symbol,num_subc,guard_interval)
%------------------------------
%FFT和去除循環前綴
%------------------------------
%輸入：
%   ofdm_symbol ----接收來自信道的OFDM符號
%   num_subc ----子載波數
%   guard_interval ----保護間隔
%輸出： 
%   rec_symbol ----移除循環前綴和經過FFT的接收信號在頻域的形式
%------------------------------
if(guard_interval>length(ofdm_symbol))
    error('The guard interval is greater than the ofdm symbol duration');
end

%The guard symbol(cyclic prefix) is removed from  the ofdm symbol
rec_time_symbol = ofdm_symbol(guard_interval+1:end);

%The FFT of the time domain signal after the removal of cyclic prefix
rec_symbol= fft(rec_time_symbol,num_subc);