48 lines
1.8 KiB
Matlab
48 lines
1.8 KiB
Matlab
function p_dpss = init_dpss(p,tau_max)
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%% init DPSS
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% channel parameters
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theta_max = tau_max * p.frame_length*100 / p.useful_carriers; % TS = 1/(p.frame_length*100)
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N_sub = floor(theta_max*p.useful_carriers)+1; % number of approximate subspace dimensions
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%N_sub = 1;
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% DPSS generation
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nDmax=min(ceil(N_sub*1.25),p.useful_carriers);
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[Udps,Sdps]=dpss(p.useful_carriers,theta_max*p.useful_carriers/2,nDmax);
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% the fftshift is needed dependig in which format the frequency response is used
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%V=fftshift(diag(exp(-2*pi*1i*theta_max/2*(0:(p.nN-1))))*Udps);
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p_dpss.V=diag(exp(-2*pi*1i*theta_max/2*(0:( p.useful_carriers-1))))*Udps;
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% compute the optimal subspace dimension based on the expected SNR
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p_dpss.SNR=0:30;
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for SNR=p_dpss.SNR
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% calculate optimum subspace dimension as bias variance tradeoff for a
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% given noise variance (assuming pilot symbols with energy one)
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sigma2 = 10.^(-SNR/10);
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[~,p_dpss.Dopt(SNR+1)]=findminimumd(sigma2, p.useful_carriers,nDmax,1/theta_max*Sdps);
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end
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% % precompute the filters for DPSS estimation for the required number of
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% % basis function
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% Dvec = min(Dopt):max(Dopt);
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% for ind=1:length(Dvec)
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% Dind = Dvec(ind);
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%
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% for itx=1:p.nant_tx
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% % f_start and t_start indicate the start of the pilots in time
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% % and frequency according to the specifications (see .doc file).
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% % t_start has to be >=2, since the first symbol is the PSS.
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% f_start = mod(itx-1,2)*2+1;
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% t_start = floor((itx-1)/2)+1;
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%
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% % filter for DPSS channel estimation
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% M = conj(diag(squeeze(transmit_f(itx,t_start,f_start:4:end))) * V(f_start:4:end,1:Dind));
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% Mpinv = (M'*M)\M.';
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% % to compute the basis coefficients do
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% % psi = Mpinv*(symb0(2:6:end));
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%
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% end
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%
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% end
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