settings.m
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上传日期：2014-07-30
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- %SETTINGS Contains the settings to use for the COFDM transmission
- % This is a common file used for the transmission and reception
- % It specifies all the link properties, channel properties,
- % data to send and filenames for input an output files
- %
- % NOTE: Not all setting combinations work as only a few have been
- % fully debugged. If the receiver is giving very high error rates,
- % then it is likely that there is a synchronisation error. If a
- % different ifft_size, NumCarr and guardtime is used this may fix the
- % error. For example: ifftsize = 2048, NumCarr = 800 guardtime = 512
- % didn't sync propoerly for the Corrs.wav data set, but changing it
- % to ifftsize = 1024, NumCarr = 400 and guardtime = 256, works.
- % Also NumCarr must be < ifftsize/2 as the generated waveform
- % is real and not complex.
- %
- % Due to processing and memory limitations, the maximum size input
- % data is approx. 20-100kB depending on the modulation scheme.
- %
- % This code is not likely to work using the student version of Matlab 4.2
- % due to the array size limitation of the student version.
- %
- % There may be some capability problems when running this code in Matlab 5.
- % I think the main problem is with the scripts used to read and write the
- % wave files. These could be changed to the in-built Matlab 5 wave scripts.
- %
- % Written by Eric Lawrey 12/8/97
- %================
- % COMMON SETTINGS
- %================
- wordsize = 8; %Number of bits per carrier per symbol to send
- %Allowable values are 1,2,4,8. 1 = BPSK, 2=QPSK, 4=16PSK, 8=256PSK
- OutWordSize = 8; %Base wordsize of input data to the COFDM transmission,
- %typically 8 bit. The input and output data is converted from
- %the OutWordSize to wordsize during the transmission
- ifftsize = 1024; %size fourier transform to generate signal (it is equal to the
- %number of samples in the symbol.) Note : must be > 2* NumCarr
- NumCarr = 400; %Number of transmission carriers
- CarrSpacing = 1; %Spacing between carriers. (1 = use all fft bins,
- %2 = every second bin)
- guardtime = 256; %Total guard time in samples.
- %(This is typically 25% of the FFT size)
- guardtype = 3; %1 = Zeroed signal, 2 = cyclic extension, 3 = half zero, half cyclic
- %Note: Only type 3 has been tested fully
- windowtype = 0; %0 = No window, 1 = Hanning window of symbol.
- %The window is applied to the base band time waveform.
- FrameGuard = ifftsize+guardtime; %Guard Time between success frames (1 symbol)
- PictureComp = 1; %Fraction of picture amplitude to compress
- %by to over come, wrap around from black to white
- %due to a phase error (set to 1 for no compression)
- DataAvg = 1; %Data Averaging, dupticate transmission of
- %data words to reduce the phase error. (Normally set to 1)
- SymbPerFrame = 30; %Number of data symbols per frame. The timing is resynchronized
- %at the start of each frame. Set to 0 if only
- %want all the data to be transmitted with one frame.
- %=====================
- % TRANSMITTER SETTINGS
- %=====================
- NoFrames = 3; %Number of duplicate data frames to generate Only valid
- %if SymbPerFrame = 0
- %==================
- % RECEIVER SETTINGS
- %==================
- quickrate = round(FrameGuard/128)+1;
- %Amount of subsampling to find the approx starting position of the
- %start frame. The larger quickrate is the faster the search is but
- %the lower the probability of finding the correct starting location.
- %quickrate needs to be lower as the SNR worsens. Typical values
- %are from 10 - 200
- %=================
- % CHANNEL SETTINGS
- %=================
- Comp = 0; %Peak Power Compression (in dB relative to peak signal power)
- %set to zero for no signal compression or clipping
- SNR = 300; %Signal to noise ratio of received signal in dB, setting > 300
- %adds no noise.
- Delay = 1; %Delay of single reflection multipath signal in samples
- %Set to 1 for no multipath.
- MultiMag = 1; %Magnitude of the reflection with respect to the direct signal
- %e.g. Setting to 0.5 makes the reflection half the amplitude of the
- %direct signal
- %====================
- % INFORMATION FORMATS
- %====================
- DataType =4; %Type of data to send in the transmission
- % 1 = random data (Amount set by NoRandData)
- % 2 = grey scale bitmap image (only the picture data is sent
- % not the file header or colour map) This is useful for high
- % error rate conditions
- % 3 = general binary data file. This allows for any data file to be
- % sent, e.g. a recorded wavefile, a gif image, a jpg image, an excel
- % document etc. The file is sent simply as a binary file with no
- % knowledge of the file structure. Thus an error in the file header
- % could corrupt the entire file. In a practical system the forward
- % error correction would be required to reduce the error to
- % an acceptable level to send general data.
- % To make the data link easier to implement the number of data words
- % sent and the number of frames used is not transmitted, but sent via
- % a file.
- % 4 = Wave Sound file. This reads in an 8bit windows 3.1 wav file
- NoRandData =12000; %Number of random data words to transmit if the DataType = 1.
- RandSeed = 1234; %Random Seed used for generating the random data sent. Both the
- %transmitter and receiver needs to know the seed. Only valid if
- %DataType = 1.
- Fs = 44100; %Sample rate of COFDM wav file generated
- res = 16; %No. bits/sample of saved wavefile
- txwavfile = 'imagetx.wav'; %Filename of the wavefile generated
- rxwavfile = 'imagetx.wav'; %Filename of the wavefile to decode
- infile = 'corrs11.wav'; %input filename of the bmp file or general file to transmit
- outfile = 'out.wav'; %Filename to store the received image
- errorfile = 'errorpic.bmp'; %Filename of the picture of the
- %errors induced in the received image.
- %Only valid for DataType = 2;
- fileknown = 1; %Indicates whether the OFDM signal file being read is known
- %i.e. whether transmitted data file exists so that the
- %exact data size can be found.
- %if fileknown = 0, the OFDM signal is read straight from
- %the file given with no regard for transmitted data file.
- %Error analysis can not be done on files read in this way
- %as there is nothing to check the received data against.
- %Also padding may be added to the received data.
- %fileknown = 1, is the normal operation where the original
- %received data is checked against the transmitted data.
- %==================================================
- %Calc Carriers used for a single wide COFDM channel
- %==================================================
- %This section calculates the carriers used to transmit the signal.
- %carriers is a vector of the carriers used in the transmission, e.g. [3,5,7,8,9]
- %Modifying carrier, allows the spectrum to be tailored to the requirements of the channel
- MidFreq = ifftsize/4; %find the middle of the spectrum
- StartCarr = MidFreq - round(((NumCarr-1)*CarrSpacing/2));
- FinCarr = MidFreq + floor(((NumCarr-1)*CarrSpacing/2));
- carriers = [StartCarr:CarrSpacing:FinCarr ]+1;
- %carriers = [2:NumCarr];
- NumCarr = length(carriers);
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