BPSK.rar_BPSK/QPSK_QPSK_QPSK ber analysis

%************************************************************************** % DIGITAL COMMUNICATION SYSTEM % BPSK MODEL %************************************************************************** %IMORTANT VARIABLES USED %t - Modeled system time %fm - Main frequency of message signal %harm - Frequency components of the message signal %amp - Amplitude of the corresonding harmonic frequency component %sampling_rate - System sampling rate . Default rate is 20 samples per cycle of maximum freqency component %range - Range of the time sampling is done . Default range is 2 cycles of minimum frequncy component %msg - Message signal to be trasnmitted %minamp - Minimum amplitude that can be used in this model %n_sample - Number of samples per cycle of the message signal %fs - Sampling frequency for sampling the message signal %msamp - Sampled version of the message signale with sampling frequency fs %no_of_levels - Number of quantization levels %quantile - Quantile interval %code - Representation levels %mq - Quantization output of sampled message signal %mq1 - Sampled version of quantized sample message signal %bits - Binary sequence of sampled quantized signal (output of ADC) %fc - Carrier signal frequency %nsamp - System Samples per cycle of carrier signal %ncyc - Number of cycles of carrier signal for one bit interval %tb - Bit interval %t_tran - Total transmission time , in order to find diffrence between already existing time variable 't' see Note-1 %mod_sig - BPSK modulated carrier signal %tran_sig - Siganl after transmission through AWGN channel , so that Awg noise is added with the original transmitted signal %f_freq - Frequency range used for visualising FFT of the signal %f_tran - Noise added transmitted signal representation in frequency domain %f_rece - Received signal after removing noise ,in frequency domain %dec_data - Binaray data extracted from BPSK modulated carrier signal %mq_rece - Decoded sampled quantized message signal data calculated from extracted binary sequence %f_out - Reconstruted signal in frequency domain after filtering %out - Reconstruted signal from the received signal ,in time domain i.e, output of the receiver %gain - gain of the amplifier expressed in ratio not in db % %ABBREVATIONS %ADC - Analog to Digital Convertor % Converts analog signal to digital signal %AWGN - Anti-White Gaussian Noise % A channel model with zero mean noise , commonly used channel model . %DAC - Digital to Analog Convertor % Converts digital signal to analog signal %Rx - Receiver %Tx - Transmitter %*****************************-TRANSMITTER-******************************** clear all; clc; %MESSAGE SIGNAL PARAMETERS fm=1e3; %Main frequency of message signal harm=[ 1 0.5 2 1 ]; %Frequency components of the message signal %In this model the message signal is represented by fourier sine series amp=[ 1 2 3 1 ]; %Amplitude of the corresonding harmonic frequency component sampling_rate=1/(20*max(fm*harm)); %System sampling rate . Default rate is 20 samples per cycle of maximum freqency component range=2/min(fm*harm); %Range of the time sampling is done . Default range is 2 cycles of minimum frequncy component t=0:sampling_rate:range; %System timing %MESSAGE SIGNAL msg=zeros(size(t)); for k=1:length(harm) msg=msg+amp(k)*sin(2*pi*harm(k)*fm*t); end minamp=min(msg); %Minimum amplitude that can be used in this model . Normally ,it need to be kept as a global constant %But for flexibility of program it is made here as variable depending on message signal value %SAMPLING n_sample=5; fs=n_sample*max(harm*fm); %Sampling ferqency . msamp=zeros(size(msg)); msamp(1:1/(fs*sampling_rate):length(t))=msg(1:1/(sampling_rate*fs):length(t)); %Sampled output signal figure(1);plot(t,msg); grid on hold on stem(t,msamp); xlabel('time');ylabel('Message signal,Sampled signal and Quantized signal'); title('MESSAGE SIGNAL , SAMPLED MESSAGE SIGNAL AND QUANTIZED SIGNAL'); legend('Message signal','Sampled Signal','Quantized Signal'); %QUANTIZATION no_of_levels=4; %Number of quantization levels quantile=(max(msamp)-min(msamp))/(no_of_levels); %Quantile interval code=min(msamp):quantile:max(msamp); %Representation levels mq=zeros(size(msamp)); for k=1:length(code) values=(( msamp>(code(k)-quantile/2) & msamp<(code(k)+quantile/2))); mq(values)=round(code(k)); %Quantization output of sampled message signal end clear values; stem(t,mq,'r*');grid on legend('Message signal','Sampled Signal','Quantized Signal'); %ENCODING if min(mq)>=0 minamp=0; end mq1=mq-round(minamp); %Shifting negative values to postive side for conversion to binary and sampling %quantized message signal bits=de2bi(mq1(1:1/(fs*sampling_rate):length(mq)),4,'left-msb')'; bits=bits(:)'; %ADC - Generating binary sequence of sampled quantized signal figure(5);stem(bits,'*r');hold on; legend('Bit sequence in Transmitter','Bit sequence in Receiver'); %PASS BAND MODULATION (BPSK) fc=1e6; %Carrier signal frequency nsamp=10; %System Samples per cycle of carrier signal ncyc=2; %Number of cycles of carrier signal for one bit interval tb=0:1/(nsamp*fc):ncyc/fc; %Bit interval t_tran=0:1/(nsamp*fc):(ncyc*length(bits))/fc+(length(bits)-1)/(nsamp*fc); %Total transmission time mod_sig=zeros(size(t_tran)); l=1; for k=1:length(tb):length(mod_sig) if(bits(l)==1) mod_sig(k:k+length(tb)-1)=cos(2*pi*fc*tb); %Phase Modulation of carrier for repesenting binary symbol one else mod_sig(k:k+length(tb)-1)=-cos(2*pi*fc*tb); %Phase Modulation of carrier for repesenting binary symbol zero end l=l+1; end %**********************AWGN-CHANNEL**************************************** tran_sig=awgn(mod_sig,10); %Transmisson of modulated carrier signal through AWGN channel figure(2);plot(t_tran,mod_sig,'.-b',t_tran,tran_sig,'r'); axis([0 3*ncyc/fc -2 2]); xlabel('time');ylabel('Tx signal and Tx signal with noise'); title('TRANSMITTED SIGNAL AND NOISE A