Research On Noncoherent Unitary Space-time Constellation Over Grassmann Manifold

MIMO wireless communication system is an information transmission with multipleantennas at both the transmitter and receiver. MIMO attracts much attention because of itsspectrum efficiency and strong resistance to fading. If the receiver has no knowledge ofchannel state information, then the communication framework is non-coherent, whereas ifthe receiver has complete channels state information, the framework is coherent. Researchresults of information theory show that the input signals which enable communication atrates approaching capacity have structure of unitary matrix. Because Grassmann manifoldis a set of linear subspace which can be formed by the columns of unitary matrix, the non-coherent unitary space time constellation design problem is equivalent to the packingproblem in the Grassmann manifold.There are many ways to design non-coherent unitary space-time constellation. In thispaper, we have studied the non-coherent unitary space-time constellation design problemover Grassmann manifold.This paper has developed the existing design method of unitary space time constellationover Grassmann manifold. Firstly, I proposed a new family of full-diversity and full-ratecoherent space time code with arbitrary size of frame. Then the non-coherent unitary spacetime codes can be built from the coherent space time code via matrix exponential map. Itis the first instance of designing constellation based on Grassmann manifold.Based on the above, this paper presents a non-coherent space-time Grassmannianconstellation with search technique. Firstly, we define a unitary matrix framework toencode the QAM symbols. Based on the distance measure of chordal Frobenius-norm, wecan get the candidate constellation points by changing the amplitude and phase of eachelement in the unitary matrix. Finally, we get the whole unitary space-time constellationwith minimum chordal Frobenius-norm maximum. Numerical simulations indicate thatthis new constellation performances better than the present codes.