158 research outputs found
A Survey of Physical Layer Security Techniques for 5G Wireless Networks and Challenges Ahead
Physical layer security which safeguards data confidentiality based on the
information-theoretic approaches has received significant research interest
recently. The key idea behind physical layer security is to utilize the
intrinsic randomness of the transmission channel to guarantee the security in
physical layer. The evolution towards 5G wireless communications poses new
challenges for physical layer security research. This paper provides a latest
survey of the physical layer security research on various promising 5G
technologies, including physical layer security coding, massive multiple-input
multiple-output, millimeter wave communications, heterogeneous networks,
non-orthogonal multiple access, full duplex technology, etc. Technical
challenges which remain unresolved at the time of writing are summarized and
the future trends of physical layer security in 5G and beyond are discussed.Comment: To appear in IEEE Journal on Selected Areas in Communication
Distributed Space Time Coding for Wireless Two-way Relaying
We consider the wireless two-way relay channel, in which two-way data
transfer takes place between the end nodes with the help of a relay. For the
Denoise-And-Forward (DNF) protocol, it was shown by Koike-Akino et. al. that
adaptively changing the network coding map used at the relay greatly reduces
the impact of Multiple Access interference at the relay. The harmful effect of
the deep channel fade conditions can be effectively mitigated by proper choice
of these network coding maps at the relay. Alternatively, in this paper we
propose a Distributed Space Time Coding (DSTC) scheme, which effectively
removes most of the deep fade channel conditions at the transmitting nodes
itself without any CSIT and without any need to adaptively change the network
coding map used at the relay. It is shown that the deep fades occur when the
channel fade coefficient vector falls in a finite number of vector subspaces of
, which are referred to as the singular fade subspaces. DSTC
design criterion referred to as the \textit{singularity minimization criterion}
under which the number of such vector subspaces are minimized is obtained.
Also, a criterion to maximize the coding gain of the DSTC is obtained. Explicit
low decoding complexity DSTC designs which satisfy the singularity minimization
criterion and maximize the coding gain for QAM and PSK signal sets are
provided. Simulation results show that at high Signal to Noise Ratio, the DSTC
scheme provides large gains when compared to the conventional Exclusive OR
network code and performs slightly better than the adaptive network coding
scheme proposed by Koike-Akino et. al.Comment: 27 pages, 4 figures, A mistake in the proof of Proposition 3 given in
Appendix B correcte
Reliable Physical Layer Network Coding
When two or more users in a wireless network transmit simultaneously, their
electromagnetic signals are linearly superimposed on the channel. As a result,
a receiver that is interested in one of these signals sees the others as
unwanted interference. This property of the wireless medium is typically viewed
as a hindrance to reliable communication over a network. However, using a
recently developed coding strategy, interference can in fact be harnessed for
network coding. In a wired network, (linear) network coding refers to each
intermediate node taking its received packets, computing a linear combination
over a finite field, and forwarding the outcome towards the destinations. Then,
given an appropriate set of linear combinations, a destination can solve for
its desired packets. For certain topologies, this strategy can attain
significantly higher throughputs over routing-based strategies. Reliable
physical layer network coding takes this idea one step further: using
judiciously chosen linear error-correcting codes, intermediate nodes in a
wireless network can directly recover linear combinations of the packets from
the observed noisy superpositions of transmitted signals. Starting with some
simple examples, this survey explores the core ideas behind this new technique
and the possibilities it offers for communication over interference-limited
wireless networks.Comment: 19 pages, 14 figures, survey paper to appear in Proceedings of the
IEE
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