474 research outputs found
Separate Source-Channel Coding for Broadcasting Correlated Gaussians
The problem of broadcasting a pair of correlated Gaussian sources using
optimal separate source and channel codes is studied. Considerable performance
gains over previously known separate source-channel schemes are observed.
Although source-channel separation yields suboptimal performance in general, it
is shown that the proposed scheme is very competitive for any bandwidth
compression/expansion scenarios. In particular, for a high channel SNR
scenario, it can be shown to achieve optimal power-distortion tradeoff.Comment: 6 pages (with an extra proof), ISIT2011, to appea
Semantically Secure Lattice Codes for Compound MIMO Channels
We consider compound multi-input multi-output (MIMO) wiretap channels where
minimal channel state information at the transmitter (CSIT) is assumed. Code
construction is given for the special case of isotropic mutual information,
which serves as a conservative strategy for general cases. Using the flatness
factor for MIMO channels, we propose lattice codes universally achieving the
secrecy capacity of compound MIMO wiretap channels up to a constant gap
(measured in nats) that is equal to the number of transmit antennas. The
proposed approach improves upon existing works on secrecy coding for MIMO
wiretap channels from an error probability perspective, and establishes
information theoretic security (in fact semantic security). We also give an
algebraic construction to reduce the code design complexity, as well as the
decoding complexity of the legitimate receiver. Thanks to the algebraic
structures of number fields and division algebras, our code construction for
compound MIMO wiretap channels can be reduced to that for Gaussian wiretap
channels, up to some additional gap to secrecy capacity.Comment: IEEE Trans. Information Theory, to appea
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