all.m

matlab仿真

%OFDM仿真程序
%参数设置
%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;		%调制前每个符号的信息bit数目，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;	%IFFT点数，size fourier transform to generate signal (it is equal to the
			%number of samples in the symbol.) Note : must be > 2* NumCarr
NumCarr = 400;		%子载波数目，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.
			%？？？？？？？用在什么地方？The window is applied to the base band time waveform.

FrameGuard = ifftsize+guardtime;  %帧信号长度，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);
%发送部分
Function BaseSignal = transmit(Datatx,ifftsize,carriers,wordsize,guardtype,guardtime,windowtype,DataAvg)
%TRANSMIT Generates a COFDM waveform from an input data.
%	  function BaseSignal = transmit(DataIn,ifftsize,carriers,...
%		    wordsize,guardtype,guardtime,windowtype,DataAvg)
%
%	  This function generates a COFDM time waveform based on the input parameters
%	  and the data given. The data is transmformed into a single frame COFDM signal. 
%	  This for the simulation of a COFDM phone system.
%	  INPUTS:
%	  ========
%	  Datatx     : Data to transmit in the wordsize given. eg. for wordsize = 2
%		       Data is from 0-3, for wordsize = 8, data is from 0-255
%		       The data should be a single row vector. See convbase.m to
%		       convert from 8bit data to the required wordsize.
%		       e.g. datatx = convbase(datain, 8, wordsize);
%	  ifftsize   : Size of ifft to use for generating the waveform
%	  carriers   : Which carriers to use for the transmission
%	  wordsize   : Number of bits to transmit on each carrier eg. 2 => QPSK
%		       1 => BPSK, 4 => 16PSK, 8 => 256PSK.
%		       Must be one of: 1,2,4 or 8
%	  guardtype  : What type of guard period to use
%		       Options:
%		       0 = No Guard period
%		       1 = zero level guard period
%		       2 = cyclic extension of end of symbols
%		       3 = same as 2 but with the first half of the guard period = zero
%	  guardtime  : Number of sample to use for the total guard time
%	  windowtype : Type of window to apply to the time waveform of the symbol
%		       Options: 
%		       0 = No windowing
%		       1 = Hamming window
%	  DataAvg    : Data Averaging. Number of repeats to send of each data word, so
%		       that the repeats can be combined at the receiver to reduce the 
%		       phase error, and thus to BER. DataAvg = 1 (No duplication)
%			
%	  OUTPUTS:
%	  ========
%	  BaseSignal : This is the output time signal for the COFDM waveform. The format
%		       of the output is a row vector.
%	  Datatx     : Data transmitted. This is the input data (DataIn) converted to 
%		       the number base used for transmission, based on wordsize.
%	  
%	  Copyright (c) Eric Lawrey 1997
%
%	  See:	RECEIVE, RDFILE.

%===============================
%	External Functions Used :
%	None

%===============================
%	Modifications:
%	8/6/97	Redo of the previous simulation script. (based on distort.m)
%	15/6/97	Continuing work on this function, currently not finished
%	16/6/97 Continued work on function, it is now finished and works, but not all 
%		the features have been tested.
%		I have tested the windowing and the zeroed guard period. The code has also
%		been optimized a bit and runs ~10 times faster then it used to, plus
%		it can handle much bigger files (tested upto 87kbytes, wordsize=4), in 35sec
%		It appears to work as a function.
%		The function needs to be changed so that it does not read the file directly
%		but instead get the data as input.
%	17/6/97	Modified the function so that it does read the input file from within 
%		the transmit function. This is so that the file can be read else where
%		then split up into smaller frames, then processed by transmit.
%		Fixed up some logical errors in the program, and removed the output phase
%		variable as it can be easily calculated from the data being transmitted.
%	12/8/97	Changed the input requirements for Datatx. It is now DataIn which is a 
%		serial vector of byte data. The base conversion, reshaping of the data
%		into symbols, and padding of the input data is done by transmit.m. I also
%		data averaging that send duplicates of the data words. The duplicates are
%		sent as the very next data word. (No the best spreading, but easy to do).

%====================
% Initialization
%====================

%rand('seed',3567);
NumCarr = length(carriers);	%find the number of carriers


%=====================
% Apply Data Averaging
%=====================
%Duplicate data to be transmitted, duplicate each dataword having the next carrier
%also transmitting the same data word. This will not give the best diversity
%performance but is the easiest to implement.
DataOut = zerohold(Datatx,DataAvg);

%=============
% Pad the Data
%=============
%Format the input serial data stream into symbols
%Reshape the data to fit the number of carriers
numsymb = ceil(length(DataOut)/NumCarr);

%If the data length is not a multiple of the number of carrier the pad the data
%with zeros
if length(DataOut)/NumCarr ~= numsymb,
	DataPad = zeros(1,numsymb*NumCarr);
	DataPad(1:length(DataOut)) = DataOut;
	DataOut = DataPad;
end

clear DataPad;

%==============================
% Reshape the data into symbols
%==============================
DataOut = reshape(DataOut,NumCarr,numsymb)';	%Reshape the data into symbols

numsymb = size(DataOut,1)+1;	%find the total number of symbols 
				%including the phase reference symbol
%========================================
% Convert to DQPSK & add phase reference
%========================================
PhaseRef = round(rand(1,NumCarr)*(2^wordsize)+0.5);	%generate random phase ref.
DPSKdata = zeros(size(DataOut,1)+1,size(DataOut,2));
DPSKdata(1,:) = PhaseRef;
for k = 1:numsymb-1
	DPSKdata(k+1,:)=rem((DataOut(k,:) + DPSKdata(k,:)-1),(2^wordsize))+1;
end
%clear DataOut;

%=====================================
%Find the required spectrums
%=====================================
[X,Y] = pol2cart(DPSKdata*(2*pi/(2^wordsize)),ones(size(DPSKdata)));
CarrCmplx = X+i*Y;

NegCarriers = ifftsize-carriers+2;	%find the bins for the negative frequency carriers
TxSpectrums = zeros(numsymb,ifftsize);

for k = 1:numsymb
	%Place the carriers used into the full spectrum
	TxSpectrums(k,carriers) = CarrCmplx(k,:);
	TxSpectrums(k,NegCarriers) = conj(CarrCmplx(k,:));
end
clear NegCarriers;
%==================================
%Find the time waveform using IFFT
%==================================
BaseSignal = real(ifft(TxSpectrums'));

clear TxSpectrums;	%Save Memory