584 research outputs found
Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey
This paper provides a comprehensive review of the domain of physical layer
security in multiuser wireless networks. The essential premise of
physical-layer security is to enable the exchange of confidential messages over
a wireless medium in the presence of unauthorized eavesdroppers without relying
on higher-layer encryption. This can be achieved primarily in two ways: without
the need for a secret key by intelligently designing transmit coding
strategies, or by exploiting the wireless communication medium to develop
secret keys over public channels. The survey begins with an overview of the
foundations dating back to the pioneering work of Shannon and Wyner on
information-theoretic security. We then describe the evolution of secure
transmission strategies from point-to-point channels to multiple-antenna
systems, followed by generalizations to multiuser broadcast, multiple-access,
interference, and relay networks. Secret-key generation and establishment
protocols based on physical layer mechanisms are subsequently covered.
Approaches for secrecy based on channel coding design are then examined, along
with a description of inter-disciplinary approaches based on game theory and
stochastic geometry. The associated problem of physical-layer message
authentication is also introduced briefly. The survey concludes with
observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with
arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials,
201
Grassmannian Beamforming for MIMO Amplify-and-Forward Relaying
In this paper, we derive the optimal transmitter/ receiver beamforming
vectors and relay weighting matrix for the multiple-input multiple-output
amplify-and-forward relay channel. The analysis is accomplished in two steps.
In the first step, the direct link between the transmitter (Tx) and receiver
(Rx) is ignored and we show that the transmitter and the relay should map their
signals to the strongest right singular vectors of the Tx-relay and relay-Rx
channels. Based on the distributions of these vectors for independent
identically distributed (i.i.d.) Rayleigh channels, the Grassmannian codebooks
are used for quantizing and sending back the channel information to the
transmitter and the relay. The simulation results show that even a few number
of bits can considerably increase the link reliability in terms of bit error
rate. For the second step, the direct link is considered in the problem model
and we derive the optimization problem that identifies the optimal Tx
beamforming vector. For the i.i.d Rayleigh channels, we show that the solution
to this problem is uniformly distributed on the unit sphere and we justify the
appropriateness of the Grassmannian codebook (for determining the optimal
beamforming vector), both analytically and by simulation. Finally, a modified
quantizing scheme is presented which introduces a negligible degradation in the
system performance but significantly reduces the required number of feedback
bits.Comment: Submitted to IEEE Journal of Selected Areas in Communications,
Special Issue on Exploiting Limited Feedback in Tomorrows Wireless
Communication Network
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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