A 16-QAM signal X, whose power is normalized as unity, is transmitted with OFDM over the discrete-time channel model h which has been used in Homework #2 and #3. As depicted in the below figure, the transmitter (TX) is now equipped with an N-point IDFT and the receiver (RX) with an N-point DFT, along with adding cyclic prefix (CP) and removing CP removal, respectively. The complex AWGN n is set with 20 dB SNR. Suppose that N=256 and the length of CP is 64. Assuming the OFDM system works with perfect synchronization. -Generate two pseudo random (PN) sequences for X, each with a length of 256 samples which are taken　{+1,-1}, and add them before the 16-QAM data with a proper CP. The OFDM frame is depicted in the following figure. PN1 and PN2 are used for channel estimation now. Suppose the PN patterns are known at RX. Use the least squares (LS) method to estimate the channel by averaging the results obtained individually　PN1 and PN2. (When perfoming the DFT window for the received signal at RX, you need to notice that the channel results in a delay of 22 samples.)