OFDM transmission over an acoustic channel

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					                             OFDM transmission over an acoustic channel
                                                                                             2010

             OFDM transmission over an acoustic channel
        Weiqing zhou (weiqing.zhou@usi.ch), Hassan Mustafa (eng.hasan.power@gmail.com)

    Part 1 Data flow of OFDM transmission over an acoustic channel.



      Binary Sequence • '011001001...
        of Meida File   ... '
                               • Mapping From Binary to Complex
                    QAM          Number.
                 Modulate      • M-ary equals to 4, 16 or 64

                              OFDM Data
                                Packet


Transmitter                         Train Packet    • Train Frames added at
                                                      head of OFDM packet
                                            • IFFT on each coloum of OFDM
                             IFFT             packet

                   Cyclic                   • add cyclic prefix
                   Prefix                     onto each coloum


                            Fianl Transmitter       • That is!
                                Sequence            • Sent to receiver




                                                                                         1
                              OFDM transmission over an acoustic channel
                                                                                                              2010



                                                       Acoustic Channel



   Remove            FFT on each         Get Channel                           OFDM              QAM
                                                            Equalization
    Prefix             coloum            Coefficient                         Demodulate        Demodulate




1.2 File description:
                                          Receiver
run.m/run_image.m: main control file. Read an audio or image as input, convert to binary sequence
format, then send to acoustic channel, reconstruct the signal after transmission, and play the audio or
show the image.
ofdm_experiment_acoustic_channel.m: OFDM transmission over acoustic channel.
qam_demod.m/qam_mod.m: QAM demodulate and modulate file.
Ber.m/ser.m: calculate BER and SER.
Image_file.mat/media_file.mat: an image and an audio signal used for testing.

Part 2 Estimation of communication system parameters

2.1 The acoustic channel is time-varying. Though the training frames are used to compensate this channel
influence, result goes worse when the size of OFDM packet grows; but too small the OFDM packet size is,
transmission rate decrease. So the first experiment is the exploration on size of OFDM packet to establish
a proper size.

Part 3 Communication system evaluation

3.1 Objective evaluation
the final Bit Error Rate is 0.09, and Symbol Error Rate is 0.19.

3.2 subjective evaluation




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