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MIMO maximum-likelihood space-time architecture

  • US 7,680,211 B1
  • Filed: 05/18/2005
  • Issued: 03/16/2010
  • Est. Priority Date: 05/18/2005
  • Status: Active Grant
First Claim
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1. A method for the design and implementation of maximum-likelihood (ML) architecture for MIMO systems with M receive antennas and N transmit antennas and with epoch T>

  • 1, comprising the steps;

    constructing the new space-time TM×

    TN transmission matrix H0 as the matrix-diagonal matrix generated by the tensor product of the T×

    T identity diagonal matrix with the M×

    N transmission matrix H to generate the TM×

    TN matrix H0 whose matrix elements on the diagonal are the H and zeros elsewhere and whereinsymbol “

    T”

    is the number of time epochs which are the number of repeated transmissions,symbol “

    TM×

    TN”

    reads “

    TM rows by TN columns”

    ,transmission matrix H has transmission elements hi,j which measure the transmitter, path, and receiver transmission loss from transmitter j in column j=1, . . . , M to receiver i in row i=1, . . . , M,transmission elements hi,j are complex measurements of the transmission loss from j to i, anda matrix-diagonal matrix has matrices along the diagonal and zeros elsewhere;

    constructing the new space-time TN×

    N code matrix C0 as the matrix product C0=A•

    B of a TN×

    TN matrix A with a TN×

    N matrix B and whereinsymbol “





    is a matrix or vector product,matrix A is the TN×

    TN matrix-diagonal matrix whose diagonal matrix elements are the T N×

    N diagonal matrices A1, . . . , AT,matrices An for n=1, . . . , T are orthogonal matrices satisfying An



    An=NIN wherein An

    is the conjugate transpose of An and IN is the N×

    N identity diagonal matrix,matrix B=[B1;

    . . . ;

    BN] is the TN×

    N matrix whose elements are the N×

    N orthogonal matrices B1, . . . , BT each with elements including L and using the Matlab construction operator “

    ;



    for stacking matrices, vectors, or elements in a column format,matrices Bn for n=1, . . . , T are orthogonal matrices with the property Bn



    Bn=NIN,matrix element “

    L”

    is the new complex-conjugate operator defined by the operation “

    L(w)=w*=complex-conjugate of the element w” and

    L(L(w))=w,space-time TN×

    N code matrix C0 satisfies the orthogonality equation C0



    C0=NIN for the column vectors of C0 wherein “

    (o)′



    is the complex-conjugate transpose of (o),current space-time TN×

    1 codes C combine the space-time codes and the transmitted data symbols,current space-time codes C cannot be factored into the product of a code matrix with the transmitted data symbol vector except for a few codes,space-time code matrix C0 architecture enables all known space-time codes C to be represented by the C0

    X architecture wherein X is the N×

    1 transmitted signal column vector and which means there exists a C0 that satisfies the identity C=C0

    X for all existing space-time codes C and for all future space-time codes C, andfactorization of the code matrix and the transmitted data symbol vector is a requirement for a ML solution;

    using an alternate construction of the new space-time TN×

    N code matrix C0 as the matrix C0=[A1

    B1;

    . . . ;

    AN

    BN] whose elements are the N×

    N matrix products An

    Bn for n=1 , , , , , T wherein the matrices An, Bn and the operator “

    ;



    are defined in the previous;

    constructing the new linear MIMO matrix transmission equation for the TM×

    1 output received data symbol vector Y
    Y=H0

    C
    0

    X+N
    o which factors out the input transmitted N×

    1 data symbol vector X and replaces the current MIMO matrix equation Y=HC+No whereincurrent MIMO practice does not factor the H and C into a matrix product since it is difficult to separate the elements of H and C and which means HC is the current MIMO TM×

    1 encoded data vector input whose elements are the space-time encoded data symbol elements multiplied by the appropriate transmission elements,receive TM×

    1 data symbol vector Y=[y(1,1);

    . . . ;

    y(M,1);

    y(M,2);

    . . . ;

    y(M,T)] elements are the detected data symbol values y(m,i) indexed on the receive antenna m=1, . . . , M and the time epoch i−

    1, . . . , T for the MIMO signal set being addressed,transmitted N×

    1 data symbol column vector X=[X1;

    . . . ;

    XN] elements are the set of N data signals Xn being transmitted over T time epochs, andNo is the TM×

    1 receive noise vector;

    implementing a new ML solution to Y=H0

    C0

    X+No to derive the estimate {circumflex over (X)} of X by solving the ML equation when L is absent
    {circumflex over (X)}=[(H0C0)′

    Q

    1
    (H0C0)]

    1
    (H0C0)′

    Q

    1
    Y wherein Q=E{N0N0

    } is the noise covariance, E{o} is the mathematical expectation of “

    o”

    , assuming the determinant det(H0



    H0)≠

    0 and det(C0



    C0)≠

    0, and when the TM×

    1 receive noise vector No is zero-mean additive white Gaussian noise (AWGN) with no cross-correlation this estimate reduces to
    {circumflex over (X)}=[(H0C0)′

    (H0C0)]

    1
    (H0C0)′

    Y and for the applications where (H0C0) is a square matrix and assuming the determinant det(H0C0)≠

    0 reduces the solution to
    {circumflex over (X)}=(H0C0)

    1
    Y; and

    implementing a new ML solution to Y=H0

    C0

    X+No to derive the estimate {circumflex over (X)} of X by solving the ML equation with L present
    {circumflex over (X)}=[H2

    1


    H
    1

    H
    1*

    1


    H
    2*]

    1


    [H
    2

    1


    H
    1*

    1


    L]•

    Y
    wherein by definition
    H0

    C
    0=H1+H2

    L
    assuming the determinant det((H0

    C0)′

    (H0

    C0))≠

    0, the TM×

    1 receive noise vector No is AWGN with no cross-correlation, and the determinant det(H1



    H1)≠

    0 and det(H2



    H2)≠

    0.

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