Abstract:
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This paper proposes a differential quantization
strategy to be used in the feedback link of a multiple-input
multiple-output (MIMO) communication system. This algorithm
is applied to the channel Gram matrix using geodesic curves and
exploiting the intrinsic geometry of positive definite Hermitian
matrices. It also exploits the temporal correlation of the channel,
and follows on average the gradient of the cost function associated
to the transmitter design criterion. A full description of the
algorithm, including the computational cost and a numerical
analysis of the effect of delays and errors in the feedback link is
presented. Simulation results show that the proposed algorithm
improves other techniques based on the direct quantization of
the channel response matrix or the quantization of the subspace
spanned by the strongest eigenmodes of the MIMO channel, i.e.,
Grassmannian based techniques. The main drawback of Grassmannian
based algorithms is that the transmitter is constrained
to apply a uniform power allocation among spatial transmission
modes, which is not forced in the algorithm proposed in this
paper. |