321 research outputs found
Robust Transceiver Design for IRS-Assisted Cascaded MIMO Systems
{Robust transceiver design against unresolvable system uncertainties is of
crucial importance for reliable communication. We consider a MIMO multi-hop
system, where the source, the relay, and the destination are equipped with
multiple antennas. Further, an intelligent reconfigurable surface (IRS) is
established to cancel the RSI as much as possible. The considered
decode-and-forward (DF) hybrid relay can operate in either half-duplex or
full-duplex mode, and the mode changes adaptively depending on the RSI
strength. We investigate a robust transceiver design problem, which maximizes
the throughput rate corresponding to the worst-case RSI under a
self-interference channel uncertainty bound constraint. To the best of our
knowledge, this is the first work that uses the IRS for RSI cancellation in
MIMO full-duplex DF relay systems. The yielded problem turns out to be a
non-convex optimization problem, where the non-convex objective is optimized
over the cone of semidefinite matrices. We propose a closed-from lower bound
for the IRS worst case RSI cancellation. Eventually, we show an important
result that, for the worst case scenario, IRS can be helpful only if the number
of IRS elements are at least as large as the size of the interference channel.
Moreover, a novel method based on majorization theory is proposed to find the
best response of the transmitters and relay against worst case RSI.
Furthermore, we propose a multi-level water-filling algorithm to obtain a
locally optimal solution iteratively. Finally, we obtain insights on the
optimal antenna allocation at the relay input-frontend and output-frontend, for
relay reception and transmission, respectively.Comment: arXiv admin note: substantial text overlap with arXiv:1912.1283
Resource Allocation for Secure Gaussian Parallel Relay Channels with Finite-Length Coding and Discrete Constellations
We investigate the transmission of a secret message from Alice to Bob in the
presence of an eavesdropper (Eve) and many of decode-and-forward relay nodes.
Each link comprises a set of parallel channels, modeling for example an
orthogonal frequency division multiplexing transmission. We consider the impact
of discrete constellations and finite-length coding, defining an achievable
secrecy rate under a constraint on the equivocation rate at Eve. Then we
propose a power and channel allocation algorithm that maximizes the achievable
secrecy rate by resorting to two coupled Gale-Shapley algorithms for stable
matching problem. We consider the scenarios of both full and partial channel
state information at Alice. In the latter case, we only guarantee an outage
secrecy rate, i.e., the rate of a message that remains secret with a given
probability. Numerical results are provided for Rayleigh fading channels in
terms of average outage secrecy rate, showing that practical schemes achieve a
performance quite close to that of ideal ones
Cooperative Jamming for Secure Communications in MIMO Relay Networks
Secure communications can be impeded by eavesdroppers in conventional relay
systems. This paper proposes cooperative jamming strategies for two-hop relay
networks where the eavesdropper can wiretap the relay channels in both hops. In
these approaches, the normally inactive nodes in the relay network can be used
as cooperative jamming sources to confuse the eavesdropper. Linear precoding
schemes are investigated for two scenarios where single or multiple data
streams are transmitted via a decode-and-forward (DF) relay, under the
assumption that global channel state information (CSI) is available. For the
case of single data stream transmission, we derive closed-form jamming
beamformers and the corresponding optimal power allocation. Generalized
singular value decomposition (GSVD)-based secure relaying schemes are proposed
for the transmission of multiple data streams. The optimal power allocation is
found for the GSVD relaying scheme via geometric programming. Based on this
result, a GSVD-based cooperative jamming scheme is proposed that shows
significant improvement in terms of secrecy rate compared to the approach
without jamming. Furthermore, the case involving an eavesdropper with unknown
CSI is also investigated in this paper. Simulation results show that the
secrecy rate is dramatically increased when inactive nodes in the relay network
participate in cooperative jamming.Comment: 30 pages, 7 figures, to appear in IEEE Transactions on Signal
Processin
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