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% Rayleigh fading %

% AUTHOR: Wenbin Luo % DATE : 04/27/01 %

% FUNCTION SYNOPSIS:

% [env,phi] = fade_diversity(L,para) %

% Parameter Description:

% L : number of samples needed % variance : variance

%********************************************************** function [env1,env2] = fade_diversity(L,variance) % Error check if variance <= 0

error('Positive variance needed') elseif nargin ~= 2

error('Insufficient input parameters') end

% Generate bivariate Gaussian uncorrelated % random variables mu = zeros(1,4); C = variance*eye(4,4); r = mvnrnd(mu,C,L);

% Convert to polar coordinates and compute

% magnitude and phase z1 = r(:,1) + j*r(:,2); z2 = r(:,3) + j*r(:,4); env1 = abs(z1); env2 = abs(z2);

%********************************************************** %*********************************************************** % This mfunction generates frequency selective % Rayleigh fading %

% AUTHOR: Wenbin Luo % DATE : 05/02/01 %

% FUNCTION SYNOPSIS: % y = fade_fs(x,L) %

% Parameter Description: %

y

: output signal

% x : input signal % L %

: number of independent Rayleigh

fading process

%********************************************************** function y = fade_fs(x,L)

% Generate bivariate Gaussian uncorrelated % random variables

tmp1 = 0:1:(L-1); tmp1 = exp(-tmp1); tmp(1:2:2*L-1) = tmp1; tmp(2:2:2*L) = tmp1;

mu = zeros(1,2*L); C = *diag(tmp); x_len = length(x); r = mvnrnd(mu,C,x_len);

% Convert to polar coordinates and compute magnitude x = x(:);

y = zeros(x_len,1); for i = 1:L,

z = r(:,2*i-1) + j*r(:,2*i); env = abs(z); %phi = angle(z); tmp_y = env.*x;

tmp_y = [zeros(i-1,1); tmp_y(1:x_len-i+1)]; y = y + tmp_y; end

%**********************************************************

%********************************************************************** % This program computes the average BER of a DS-SS/BPSK %

communication system with binary BCH code in the AWGN channel

%

% AUTHOR: Wenbin Luo % DATE : 04/28/01 % % %

%**********************************************************************

%function Plot_Pe = final11_extra() clear all; %close all;

format long;

%set up the threshold Vt Vt = 0;

Plot_Pe = []; N = 16; x_num = 2500; plot_EbNo = -20:2:10; for EbNo = -20:2:10,

%convert back from dB Eb_No = EbNo; ?

Eb_No = 10.^(Eb_No/10); %assume No = 2; No = 2;

Eb = No * Eb_No; êlculate power p Tc = 1; Ts = N * Tc; p = Eb / Ts;

%generate BPSK symbols randomly with value +1 or -1 x = bingen(x_num); x_org = x;

-ds error-correcting code

enc_N = 15; enc_K = 5; %7/4 or 15/5 x(find(x < 0)) = 0;

x = encode(x,enc_N,enc_K,'bch'); x = x';

x(find(x == 0)) = -1;

%DS-SS modulate symbols with user code c = bingen(N); y = ds_mod(c(:),x);

%scale by appropriate power factor