258 research outputs found
Diversity-Multiplexing Tradeoff for the MIMO Static Half-Duplex Relay
In this work, we investigate the diversity-multiplexing tradeoff (DMT) of the
multiple-antenna (MIMO) static half-duplex relay channel. A general expression
is derived for the DMT upper bound, which can be achieved by a
compress-and-forward protocol at the relay, under certain assumptions. The DMT
expression is given as the solution of a minimization problem in general, and
an explicit expression is found when the relay channel is symmetric in terms of
number of antennas, i.e. the source and the destination have n antennas each,
and the relay has m antennas. It is observed that the static half-duplex DMT
matches the full-duplex DMT when the relay has a single antenna, and is
strictly below the full-duplex DMT when the relay has multiple antennas.
Besides, the derivation of the upper bound involves a new asymptotic study of
spherical integrals (that is, integrals with respect to the Haar measure on the
unitary group U(n)), which is a topic of mathematical interest in itself.Comment: 19 pages, 2 figures, submitted to the IEEE Transactions on
Information Theor
Cooperative Lattice Coding and Decoding
A novel lattice coding framework is proposed for outage-limited cooperative
channels. This framework provides practical implementations for the optimal
cooperation protocols proposed by Azarian et al. In particular, for the relay
channel we implement a variant of the dynamic decode and forward protocol,
which uses orthogonal constellations to reduce the channel seen by the
destination to a single-input single-output time-selective one, while
inheriting the same diversity-multiplexing tradeoff. This simplification allows
for building the receiver using traditional belief propagation or tree search
architectures. Our framework also generalizes the coding scheme of Yang and
Belfiore in the context of amplify and forward cooperation. For the cooperative
multiple access channel, a tree coding approach, matched to the optimal linear
cooperation protocol of Azarain et al, is developed. For this scenario, the
MMSE-DFE Fano decoder is shown to enjoy an excellent tradeoff between
performance and complexity. Finally, the utility of the proposed schemes is
established via a comprehensive simulation study.Comment: 25 pages, 8 figure
Optimal space-time codes for the MIMO amplify-and-forward cooperative channel
In this work, we extend the non-orthogonal amplify-and-forward (NAF)
cooperative diversity scheme to the MIMO channel. A family of space-time block
codes for a half-duplex MIMO NAF fading cooperative channel with N relays is
constructed. The code construction is based on the non-vanishing determinant
criterion (NVD) and is shown to achieve the optimal diversity-multiplexing
tradeoff (DMT) of the channel. We provide a general explicit algebraic
construction, followed by some examples. In particular, in the single relay
case, it is proved that the Golden code and the 4x4 Perfect code are optimal
for the single-antenna and two-antenna case, respectively. Simulation results
reveal that a significant gain (up to 10dB) can be obtained with the proposed
codes, especially in the single-antenna case.Comment: submitted to IEEE Transactions on Information Theory, revised versio
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