Integrated Wireless-pon access Network Architectures Milos Milosavljevic

A.2.1 FFT and Channel Equalisation
A.2.1.1
 
FFT 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% %
%% Name: receiver.m %
%% %
%% Description: This function performs FFT and CP removal %
%% %
%% Parameters: %
%% SymbolRx = QAM symbols. SymbolTx = OFDM symbol %
%% margin = CP size in samples. %
%% %
%% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function
SymbolRx=receiver(SymbolTx, Guard, Nfft)
%Cyclic prefix removal
margin=length(SymbolTx)*Guard;
margin=margin/(1+Guard);
cyclic_removed=SymbolTx(margin+1:end);
%FFT
SymbolRx=fft(cyclic_removed,Nfft); 
A.2.1.2
 
Channel equalisation 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% %
%% Name: chanelestimate.m %
%% %
%% Description: This code estimates the channel coefficients and %
%% perform data recovery. %
%% %
%% %
%% Parameters: %
%% data_rx = Equalised symbols. estimate = channel coeficients % 
%% 
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function
data_rx = channelestimate(dataafterFFT,channel)
estimate = fft(channel,256);
estimate = conj(estimate');
data_rx = dataafterFFT ./ estimate; 

---

 
172 
A.3
 
Multi-path SUI Channel Modelling
function
channel = channelSUI(N_SUI,G,BW)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% %
%% Name: channelSUI.m %
%% %
%% Description: The function generates the Channel Impulse Response %
%% of the channel variant by using Jakes Model. %
%% %
%% SUI channels from 1-6 with different bandwidths could be simulated %
%% %
%% %
%% Parameters: %
%% n = Oversampling factor. channel = output coefficients %
%% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Nfft = 256;
% fixed WiMAX
BW = BW*1e6;
% oversampling factor defined by 802.16d
if
mod(BW,1.75)==0
n = 8/7;
elseif
mod(BW,1.5)==0
n = 86/75;
elseif
mod(BW,1.25)==0
n = 144/125;
elseif
mod(BW,2.75)==0
n = 316/275;
elseif
mod(BW,2)==0
n = 57/50;
else
n = 8/7;
end
Fs = floor(n*BW/8000)*8000; 
% Oversampling rate
deltaF = Fs / Nfft;
% OFDM subcarrier spacing
Tb = 1/deltaF;
% Symbol duration
Ts = Tb * (1+G);
% Symbol duration with CP
T = 1/(Fs*1e-6);
% OFDM symbol duration
[variances,Lc,Dop]=CIRpowers(N_SUI,T); 
% variance calculated
hfr=[];
for
ih=1:Lc+1
hfr=[hfr;genh(FrameLength,Dop,Ts)]; 
% generates coefs according to 
Jakes Model
end
hfr=diag(variances.^0.5)*hfr;
% Channel coefficients are normilised.
channel = hfr ./ norm(hfr); 

---

 
173 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% %
%% Name: CIRpowers.m %
%% %
%% Description: It generates variance of each path of the channel %
%% %
%% %
%% Parameters: %
%% SUI = Channel type to simulate. T = Symbol duration %
%% tap_variances = Output variance. BW = Bandwidth of the channel % 
%%
L= length of the variance
%
%% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function
[tap_variances,L,Dop]=CIRpowers(SUI,T)
[powers,K,delays,Dop,ant_corr,Fnorm] = SUI_parameters(SUI);
Dop = max (Dop);
delays=delays/T; 
% delay expressed in terms of samples
nbtaps=length(powers);
% Number of paths
len_cir=1+round(max(delays)); 
% Length of the channel impulse response
tap_variances=zeros(1,len_cir); 
% Output variance variable initialisation
variances=10.^(powers/10);
% convert power to linear units
variances=variances/sum(variances); 
% normalise the variance
for
i=1:nbtaps
tap_variances(1+round(delays(i)))=tap_variances(1+round(delays(i)))+ 
variances(i);
end
L=length(tap_variances)-1;