bài số 1 mô phỏng kênh rayleigh theo phương pháp rice

rs_i=rs_framei,:+ISI; else rs_i=rs_framei,:; end; %Giai ma OFDM Demodulated_signal_i=OFDM_Demodulatorrs_i,NFFT,NFFT,G; d=Demodulated_signal_i./H; demodulated_symbol_i=ddemodced,1,1,''''QAM''''

Ph l c ụ ụ

Mã ngu n Matlab và các k t qu mô ph ng ồ ế ả ỏ

Bài s 1: Mô ph ng kênh Rayleigh theo ph ố ỏ ươ ng pháp Rice

Bài 1.1: Tính các thông s f, C, ố θ:

%================================

%Tinh cac thong so f, C, th

%================================

clear

f_m=91; %Tan so Doppler lon nhat

b=1; %Phuong sai cua qua trinh g(t)

N1=9; %So phan tu g(t) phan thuc mo phong

N2=10; % So phan tu g(t) phan ao mo phong

for n=1:1:N1;

c1(n)=sqrt(2*b/N1);

f1(n)=f_m*sin(pi*(n-0.5)/(2*N1));

th1(n)=2*pi*n/(N1+1);

end

for n=1:1:N2;

c2(n)=sqrt(2*b/N2);

f2(n)=f_m*sin(pi*(n-0.5)/(2*N2));

th2(n)=2*pi*n/(N2+1);

end

save ex4p1_Res f1 f2 c1 c2 th1 th2

Bài 1.2: L p hàm g.m đ tính toán ậ ể

%=======================================

%Ham tao qua trinh g(t)

%=======================================

function y=g(c,f,th,t)

y=zeros(size(t));

for n=1:length(f);

y=y+c(n)*cos(2*pi*f(n).*t+th(n));

end;

Bài 1.3: Vi t hàm đ đ a ra biên đ kênh ế ể ư ộ và v hàm : ẽ

%=====================================

%Tinh bien do kenh va ham alpha

%=====================================

clear;

load ex4p1_Res f1 f2 c1 c2 th1 th2

f_s=270800; %Tan so lay mau

T_sim=0.4; %Thoi gian mo phong

t=0:1/f_s:T_sim; % Thoi gian mo phong t

g1=g(c1,f1,th1,t);

g2=g(c2,f2,th2,t);

g=g1+j*g2;

alpha=abs(g);

alpha_dB=20*log10(alpha);

Hoàng S Tân – MSSV: 20083473 – L p ĐT3-K53 ỹ ớ

title('Bien do kenh (dB)');

xlabel('\alpha(t)');

legend('\alpha(t)in dB',0);

Đ th : ồ ị

Bài 1.4: xác đ nh các thông s giá tr trung bình, đ bi n đ i, hàm m t đ xác su t (PDF): ị ố ị ộ ế ổ ậ ộ ấ

%======================================

%Ham tinh gia tri trung binh va

% do bien doi cua g1(t), g(t), alpha(t)

%Ham mat do xac suat cua cac qua trinh

% bang bieu do

%======================================

clear;

load ex4p1_Res f1 f2 c1 c2 th1 th2

f_s=50000; %Tan so lay mau

T_sim=20; %Thoi gian mo phong

t=0:1/f_s:T_sim;

g1=g(c1,f1,th1,t);

g2=g(c2,f2,th2,t);

g=g1+j*g2;

mean_g=mean(g); %Gia tri trung binh cua g

mean_g1=mean(g1); % Gia tri trung binh cua g1

mean_alpha=mean(alpha); % Gia tri trung binh cua alpha

var_g=var(g); %Do bien doi cua g

var_g1=var(g1); % Do bien doi cua g1

var_alpha=var(alpha); % Do bien doi cua alpha

n=length(alpha);

x=0:0.1:3; %Thoi gian tinh bang giay

b=hist(alpha,x); %Bieu do mat do xac suat cua alpha

figure(1);

stem(x,b/n/(x(2)-x(1)));%Ve tin hieu roi rac

hold on;

k=0; %He so k'=s^2/(2*b_0)

total_p=2; %Cong suat nhan duoc

alpha_p=(2.*x.*(k+1)/total_p).*exp(-k-((k+1).*x.^2/total_p)).*besseli(0, (2.*x.*sqrt(k*(k+1)/total_p)));

plot(x,alpha_p,'r');

title('Mat do xac suat cua alpha(x)');

xlabel('x');

ylabel('P_{\alpha}(x)');

legend('p_{\alpha}(x)' 'Phan bo Rayleigh', );

hold off;

figure(2);

n1=length(g1);

x1=-4:0.1:4;

c=hist(g1,x1); %Bieu do mat do xac suat cua g1

stem(x1,c/n1/(x1(2)-x1(1)));

hold on;

p=(1/sqrt(2*pi))*exp(-x1.^2/2);

plot(x1,p,'r');

title('Mat do xac suat PDF cua g1');

xlabel('x');

ylabel('P_{g1}(x)');

legend('p_{g1}(x)' 'Phan bo Gaussian', );

hold off;

Đ th : ồ ị

Hoàng S Tân – MSSV: 20083473 – L p ĐT3-K53 ỹ ớ

Hoàng S Tân – MSSV: 20083473 – L p ĐT3-K53 ỹ ớ

Bài s 2: Mô hình kênh Fadding phân t p đa đ ố ậ ườ ng theo ph ươ ng pháp

Monte Carlo

Bài 2.1: Mô hình kênh phân t p đa đ ậ ườ ng :

Hàm mô hình Monte Carlo

%==========================================================================

%Ham mo hinh kenh phan tap da duong theo phuong phap Monte Carlo

%========================================================================== function [h,t_next]

=MCM_channel_model(u,initial_time,number_of_summations,symbol_duration,f_dmax ,channel_coefficients);

%u la bien ngau nhien duoc dung de roi rac tan so, pha cua hieu uong Doppler

%number_of_summation: so luong hoac pha roi rac duoc su dung trong

%phuong phap Monte Carlo

%symbol+duration la khoang thoi gian lay mau cua tin hieu

%f_fmax La tan so Doppler lon nhat

t=initial_time; %thoi gian bat dau quan sat kenh

Channel_Length=length(channel_coefficients); % Chieu dai dap ung kenh

h_vector=[]; %Vector mo hinh CIR

for k=1:Channel_Length;

u_k=u(k,:);

%Mot bien ngau nhien cua k

phi=2*pi*u_k;

%tan so Doppler roi rac su dung trong Monte Carlo

f_d=f_dmax*sin(2*pi*u_k);

h_tem=channel_coefficients(k)*1/

(sqrt(number_of_summations))*sum(exp(j*phi).*exp(j*pi*f_d*t));

h_vector=[h_vector,h_tem];

end;

h=h_vector;

t_next=initial_time+symbol_duration;

end

Ch ươ ng trình chính:

%==========================================================================

%Chuong trinh chinh mo phong phuong phap Monte Carlo

%==========================================================================

clear all;

%Dat cac thong so

NFFT=64; %Chieu dai FFT

t_a=8.0000e-007; %Thoi gian lay mau tin hieu 1/t_a

T_S=NFFT*t_a; %Thoi gian quan sat

number_of_summations=40;

f_dmax=0.0; %Tan so Doppler lon nhat

channel_profile=[1.0000,0.8487,0.7663,0.7880,0.6658,0.6658,0.5174,0.0543,0.04 56];

%He so cong suat tre

rho=channel_profile;

N_P=length(rho); %Chieu dai dap ung kenh

u=rand(N_P,number_of_summations);

%Bien ngau nhien

h=[]; %vector CIR

H=[]; %vector CTF

for i= 1:100;

h_i=MCM_channel_model(u,initial_time,number_of_summations,T_S,f_dmax,rho); h_i_tem=[h_i,zeros(1,NFFT-N_P)];

H_i_tem=fft(h_i_tem);

H_i=[H_i_tem(NFFT/2+1:NFFT),H_i_tem(1:NFFT/2)];

initial_time=initial_time+T_S;

h=[h;h_i];

H=[H;H_i];

end;

figure(2);

mesh(abs(H))

xlabel('f in B=1.25MHz')

ylabel('t in 1.024e-0.4s')

zlabel('H(f,t)')

title('f_{D,max}=0.0Hz')

L n l ầ ượ t thay b ng 0.0Hz, 5.0Hz và 500.0Hz ta có k t qu mô ph ng: ằ ế ả ỏ

Đ th : ồ ị

Hoàng S Tân – MSSV: 20083473 – L p ĐT3-K53 ỹ ớ

Hoàng S Tân – MSSV: 20083473 – L p ĐT3-K53 ỹ ớ

Bài 2.2: So sánh hàm t t ự ươ ng quang th i gian c a kênh cho 2 tr ờ ủ ườ ng h p: ợ

%==========================================================================

%chuong trinh uoc luong ham tu tuong tuong quan thoi gian cua kenh

%==========================================================================

clear all;

NFFT=64;

t_a=8.0000e-007;

T_S=NFFT*t_a;

number_of_summations=40;

f_dmax1=90.0;

f_dmax2=9.0;

channel_profile=[1.0000,0.8487,0.7663,0.7880,0.6658,0.5644,0.5174,0.0543,0.04 65];

rho=channel_profile;

N_P=length(rho);

u=rand(N_P,number_of_summations);

T_S=NFFT*t_a;

NofSymbol=1000;

t=0.1;

H_sequence1=[];

[h1]=MCM_channel_model(u,t,number_of_summations,T_S,f_dmax1,rho); [h2]=MCM_channel_model(u,t,number_of_summations,T_S,f_dmax2,rho); h_extended1=[h1,zeros(1,NFFT-length(h1))];

h_extended2=[h2,zeros(1,NFFT-length(h2))];

H1=fft(h_extended1);

H2=fft(h_extended2);

H_f11=H1(3);

H_f12=H2(3);

H_sequence1=[H_sequence1,H_f11];

H_sequence2=[H_sequence2,H_f12];

t=t+T_S;

end;

time_autoc1=xcorr(H_sequence1,'coeff');

time_autoc2=xcorr(H_sequence2,'coeff');

tau1=-(NofSymbol-1)*T_S:T_S:(NofSymbol-1)*T_S;

tau2=-(NofSymbol-1)*T_S:T_S:(NofSymbol-1)*T_S;

plot(tau1,real(time_autoc1),'k.');

xlabel('\Delta t (s)');

ylabel('Tuong quan thoi gian R(\Delta t)');

hold on;

plot(tau2,real(time_autoc2),'k.');

legend('f_{D,max}=9.0Hz' 'f_{D,max}=90.0Hz', );

Đ th : ồ ị

Hoàng S Tân – MSSV: 20083473 – L p ĐT3-K53 ỹ ớ

Bài s 3: Mô ph ng h th ng OFDM qua kênh vô tuy n ố ỏ ệ ố ế

Bài 3.1: mô ph ng h th ng đa sóng mang t n tr c giao (OFDM) s d ng các thông s l y t ỏ ệ ố ầ ự ử ụ ố ấ ừ chu n HyperLAN/2: ẩ

Code hàm “OFDM_Modulator”

function [y] = OFDM_Modulator(data,NFFT,G)

chnr=length(data);

N=NFFT;

x=[data,zeros(1,NFFT-chnr)];

a=ifft(x);%fft

y=[a(NFFT-G+1:NFFT),a];%chen khoang bao ve

end

Code hàm “OFDM_Demodulator”

function [y] = OFDM_Demodulator(data,chnr,NFFT,G)

%Chen khoang bao ve

x_remove_gaurd_interval=[data(G+1:NFFT+G)];

x=fft(x_remove_gaurd_interval);

y=x(1:chnr);

end

Code ch ươ ng trình chính:

%=============================

%Chuong trinh chinh

clear all;

NFFT=64; %Chieu dai NFFT

G=9; %Khoang bao ve

M_ary=16; %Dang dieu che QAM

t_a=50*10^(-9);%Thoi gian lay mau

channel_profile=[1.0000,0.8487,0.7663,0.7880,0.6658,0.5644,0.5174,0.0543,0.04 65];

rho=channel_profile;

h=sqrt(rho);

N_P=length(rho);

H=fft([h,zeros(1,NFFT-N_P)]);

NofOFDMSymbol=100; %So ky tu cua OFDM

length_data=(NofOFDMSymbol)*NFFT; %Chieu dai tong cong cua du lieu

%Bits nguon

source_data=randint(length_data,sqrt(M_ary));

%Bit de ma hoa

symbols=bi2de(source_data);

%Dieu che QAM trong dai tan co so

QAM_Symbol=dmodce(symbols,1,1,'qam',M_ary);

%Chuan bi lay mau du lieu

Data_Pattern=[];

for i=0:NofOFDMSymbol-1;

QAM_tem=[];

for n=1:NFFT;

QAM_tem=[QAM_tem,QAM_Symbol(i*NFFT+n)];

end;

Data_Pattern=[Data_Pattern;QAM_tem];

clear QAM_tem;

end;

ser=[];%Dat so ky tu bi loi la vector rong

snr_min=0;

snr_max=25;

step=1;

for snr=snr_min:step:snr_max;

snr=snr-10*log10((NFFT-G)/NFFT);

rs_frame=[];%Ma tran tin hieu nhan

for i=0:NofOFDMSymbol-1;

%Dieu che OFDM

OFDM_signal_tem=OFDM_Modulator(Data_Pattern(i+1,:),NFFT,G);

%Tin hieu nhan duoc qua kenh da duong duoc tao ra boi phep chap

rs=conv(OFDM_signal_tem,h);

%Nhieu duoc them vao

rs=awgn(rs,snr,'measured' 'dB', );

rs_frame=[rs_frame;rs];

clear OFDM_signal_tem;

end;

%Nhan tin hieu

Receiver_Data=[];%Chuan bi ma tran de nhan ky tu

d=[];%Ky tu giai ma

data_symbol=[];

for i=1:NofOFDMSymbol;

if(N_P>G+1)&(i>1)

previous_symbol=rs_frame(i-1,:);

ISI_term=previuos_symbol(NFFT+2*G+1:NFFT+G+N_P-1);

Hoàng S Tân – MSSV: 20083473 – L p ĐT3-K53 ỹ ớ

rs_i=rs_frame(i,:)+ISI;

else

rs_i=rs_frame(i,:);

end;

%Giai ma OFDM

Demodulated_signal_i=OFDM_Demodulator(rs_i,NFFT,NFFT,G);

d=Demodulated_signal_i./H;

demodulated_symbol_i=ddemodce(d,1,1,'QAM',M_ary);

data_symbol=[data_symbol,demodulated_symbol_i];

end;

data_symbol=data_symbol';

%Tinh toan ky tu loi

[number,ratio]=symerr(symbols,data_symbol);

ser=[ser,ratio];

end;

snr=snr_min:step:snr_max;

semilogy(snr,ser,'bo');

ylabel('SER');

xlabel('SNR in dB');

K t qu mô ph ng: ế ả ỏ

Bài 3.2: Thay G=0 (không có kho ng b o v ) và công su t tr : ả ả ệ ấ ễ

channel_profile=[1.0000,0.6095,0.4945,0.3940,0.2371,0.1900,0.1159,0.0699,0.0462];

ta có đ th SER c a h th ng: ồ ị ủ ệ ố

Hoàng S Tân – MSSV: 20083473 – L p ĐT3-K53 ỹ ớ