www.gusucode.com > LTE仿真Matlab源码 > LTE_channel_estimator_mini.m
function [channel_estimate] = LTE_channel_estimator_mini(LTE_params, rx_ref_symbols, RefSym, RefMapping, sigma_n2, y_rx_assembled)
% LTE channel estimator for mini receiver- to filter the output of the transmitter.
% [chan_output] = LTE_channel_model(BS_output, SNR)
% Author: Michal Simko, msimko@nt.tuwien.ac.at
% (c) by INTHFT
% www.nt.tuwien.ac.at
%
% input : ChanMod ... struct -> include info about filtering type, channel autocorrelation matrix
% output: channel_estimate ... [ x ] matrix of estimate of channel coefficients
%
% date of creation: 2010/11/16
% global LTE_params;
%% Channel estimator
channel_estimate = nan(LTE_params.Ntot,LTE_params.Nsub,LTE_params.UE_config.nRX,LTE_params.BS_config.nTx);
interpolation = false;
channel_estimation_method = LTE_params.UE_config.channel_estimation_method;
channel_interpolation_method = LTE_params.UE_config.channel_interpolation_method;
filtering = 'BlockFading';
for tt = 1:LTE_params.BS_config.nTx
for rr = 1:LTE_params.UE_config.nRX
switch filtering
case 'BlockFading'
switch channel_estimation_method
case 'LS' %LS for block fading
H_ls_one_channel = rx_ref_symbols(:,:,tt,rr)./RefSym(:,:,tt);
[position_freq,position_time] = find(RefMapping(:,:,tt)); %positons of reference symbols
if(tt>2)
%position = reshape(position_freq,length(position_freq)/2,2); %form the position of reference symbols to appropriate matrix
[notused reference_mapping] = sort(position_freq); %find the real order of reference symbols in frequency
H_ls_one_channel = reshape(H_ls_one_channel,length(position_freq),2);
H_ls_one_channel(:,2) = [];
else
position = reshape(position_freq,length(position_freq)/2,2); %form the position of reference symbols to appropriate matrix
[notused reference_mapping] = sort(position(:,1)); %find the real order of reference symbols in frequency
H_ls_one_channel = reshape(H_ls_one_channel,length(position_freq)/2,2);
end
H_ls_one_channel = mean(H_ls_one_channel,2);
H_ls_one_channel = H_ls_one_channel(reference_mapping);
interpolation = true;
case {'GENIE','GENIE_ALMMSE'}
%do nothing
otherwise
error('channel estimation not supported');
end
if(interpolation)
switch channel_interpolation_method
case {'linear', 'cubic', 'spline'}
first_ref_sym = min(position_freq); %position of first refernce symbol
channel_estimate_help = interp1(first_ref_sym:3:LTE_params.Ntot,H_ls_one_channel,1:LTE_params.Ntot,channel_interpolation_method,'extrap');
channel_estimate_help = channel_estimate_help.';
case 'sinc_freq'
pulse = zeros(LTE_params.Ntot,1);
first_ref_sym = min(position_freq); %position of first refernce symbol
pulse(first_ref_sym:3:end) = H_ls_one_channel;
channel_estimate_help = conv(pulse,sinc((-LTE_params.Ntot:LTE_params.Ntot)/3));
channel_estimate_help = channel_estimate_help((LTE_params.Ntot +1 ):(LTE_params.Ntot + LTE_params.Ntot)).';
case 'sinc_time'
pulse = zeros(LTE_params.Ntot,1);
first_ref_sym = min(position_freq); %position of first refernce symbol
pulse(first_ref_sym:3:end) = H_ls_one_channel;
PULSE = ifft(pulse,LTE_params.Nfft);
N = 3*[ones(floor(LTE_params.Nfft/(3*2)),1);zeros(LTE_params.Nfft - 2*floor(LTE_params.Nfft/(3*2)),1);ones(floor(LTE_params.Nfft/(3*2)),1)]; %rect
channel_time = PULSE.*N;
channel_estimate_help = fft(channel_time,LTE_params.Nfft);
channel_estimate_help = channel_estimate_help(1:LTE_params.Ntot);
case 'T-F'
first_ref_sym = min(position_freq); %position of first refernce symbol
channel_estimate_help = interpft(H_ls_one_channel,LTE_params.Ntot);
channel_estimate_help = circshift(channel_estimate_help,first_ref_sym-1);
otherwise
error('interpolation method not supported')
end
channel_estimate(:,:,rr,tt) = repmat(channel_estimate_help,1 , LTE_params.Nsub);
end
otherwise
error('not supported filtering type')
end
end
end
switch filtering
case 'BlockFading'
switch channel_estimation_method
case 'GENIE' %LS for block fading
% A = [];
% for ii = 1:LTE_params.Nsub
% A = [A;eye(ChanMod.nRX)];
% end
% B = [];
% for ii = 1:LTE_params.Nsub
% B = [B,eye(ChanMod.nTX)];
% end
A = [];
B = [];
index_vec = [1 2 3 4 5 6 7 8 9 10 11 12 13 14];
for sub_i = 1:LTE_params.Ntot
y_tx_assembled_genie_sub = conj(squeeze(y_tx_assembled_genie(sub_i,index_vec,:)));
if ChanMod.nTX == 1
y_tx_assembled_genie_sub = y_tx_assembled_genie_sub(:);
end
if rank(y_tx_assembled_genie_sub)~=ChanMod.nTX
A = [A;sub_i];
elseif rank(y_tx_assembled_genie_sub)==ChanMod.nTX
B = [B;sub_i];
y_rx_assembled_sub = conj(squeeze(y_rx_assembled(sub_i,index_vec,:)));
y_rx_assembled_sub = y_rx_assembled_sub(:);
kron_matrix = kron(eye(ChanMod.nRX),y_tx_assembled_genie_sub);
LS_matrix = inv(kron_matrix'*kron_matrix)*kron_matrix';
channel_help = LS_matrix*y_rx_assembled_sub;
channel_help = reshape(channel_help,ChanMod.nTX,ChanMod.nRX)';
channel_estimate(sub_i,1,:,:) = channel_help;
end
%y_tx_assembled_genie_sub =
%y_tx_assembled_genie_sub(:);
end
for tt = 1:ChanMod.nTX
for rr = 1:ChanMod.nRX
channel_estimate_help = interp1(B,squeeze(channel_estimate(B,1,rr,tt)),1:LTE_params.Ntot,channel_interpolation_method,'extrap');
channel_estimate_help = channel_estimate_help.';
channel_estimate(:,1,rr,tt) = channel_estimate_help;
end
end
channel_estimate = repmat(channel_estimate(:,1,:,:),[1,LTE_params.Nsub,1,1]);
end
end