Cedric Roux
56c66c09aa
Pre-ci test passed git-svn-id: http://svn.eurecom.fr/openair4G/trunk@4000 818b1a75-f10b-46b9-bf7c-635c3b92a50f
66 lines
1.8 KiB
Matlab
Executable File
66 lines
1.8 KiB
Matlab
Executable File
%MAC to BC Transformation
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%Authors: Nihar Jindal, Wonjong Rhee, Sriram Vishwanath, Syed Jafar, Andrea
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%Goldsmith
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%Date: 6/20/05
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function Downlink = MAC_to_BC(H, Uplink);
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%assumes users decoded in increasing order for uplink: 1,2,...,K,
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%opposite encoding order for downlink (K, K-1,..., 1)
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%Function Inputs
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%H: triply indexed UPLINK channel
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% H(:,:,k) refers to the UPLINK channel of the kth receiver
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% H(:,:,k) is an (M x N) matrix
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%Uplink: triply indexed matrices containing the UPLINK covariance matrices
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% Uplink(:,:,k) is the (N x N) covariance of user k
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%Function Outputs
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%Downlink: triply indexed matrices containing the DOWNLINK covariance matrices
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% Downlink(:,:,k) is the (M x M) covariance of user k
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%Other Variables
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%M: # of transmit antennas in downlink channel
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%N: # of receive antennas in downlink channel
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%K: # of receivers
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%Determine # of antennas, users
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[M,N,K] = size(H);
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for k = 1:K
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%Compute A_i (equation 34)
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temp_sum = eye(M,M);
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for l = (k+1):K
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temp_sum = temp_sum + H(:,:,l) * Uplink(:,:,l) * H(:,:,l)';
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end;
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B(:,:,k) = temp_sum;
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%Compute B_i (equation 34)
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temp_sum = eye(N,N);
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for l = 1:(k-1)
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temp_sum = temp_sum + H(:,:,k)' * Downlink(:,:,l) * H(:,:,k);
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end;
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A(:,:,k) = temp_sum;
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%take SVD of effective channel
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Hk_eff = B(:,:,k)^(-0.5) * H(:,:,k) * A(:,:,k)^(-0.5);
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[r,t] = size(Hk_eff);
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if (t > r)
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[F,D,G] = svd(Hk_eff',0);
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Fk = G;
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Gk = F;
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else
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[Fk,D,Gk] = svd(Hk_eff,0);
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end;
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%Compute downlink covariance (equation 35)
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Downlink(:,:,k) = B(:,:,k)^(-0.5) * Fk * Gk' * A(:,:,k)^(0.5) * Uplink(:,:,k) * A(:,:,k)^(0.5) * Gk * Fk' * B(:,:,k)^(-0.5);
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end;
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