170 research outputs found
The Relay-Eavesdropper Channel: Cooperation for Secrecy
This paper establishes the utility of user cooperation in facilitating secure
wireless communications. In particular, the four-terminal relay-eavesdropper
channel is introduced and an outer-bound on the optimal rate-equivocation
region is derived. Several cooperation strategies are then devised and the
corresponding achievable rate-equivocation region are characterized. Of
particular interest is the novel Noise-Forwarding (NF) strategy, where the
relay node sends codewords independent of the source message to confuse the
eavesdropper. This strategy is used to illustrate the deaf helper phenomenon,
where the relay is able to facilitate secure communications while being totally
ignorant of the transmitted messages. Furthermore, NF is shown to increase the
secrecy capacity in the reversely degraded scenario, where the relay node fails
to offer performance gains in the classical setting. The gain offered by the
proposed cooperation strategies is then proved theoretically and validated
numerically in the additive White Gaussian Noise (AWGN) channel.Comment: 33 pages, submitted to IEEE Transactions on Information Theor
Polar Coding for Secure Transmission and Key Agreement
Wyner's work on wiretap channels and the recent works on information
theoretic security are based on random codes. Achieving information theoretical
security with practical coding schemes is of definite interest. In this note,
the attempt is to overcome this elusive task by employing the polar coding
technique of Ar{\i}kan. It is shown that polar codes achieve non-trivial
perfect secrecy rates for binary-input degraded wiretap channels while enjoying
their low encoding-decoding complexity. In the special case of symmetric main
and eavesdropper channels, this coding technique achieves the secrecy capacity.
Next, fading erasure wiretap channels are considered and a secret key agreement
scheme is proposed, which requires only the statistical knowledge of the
eavesdropper channel state information (CSI). The enabling factor is the
creation of advantage over Eve, by blindly using the proposed scheme over each
fading block, which is then exploited with privacy amplification techniques to
generate secret keys.Comment: Proceedings of the 21st Annual IEEE International Symposium on
Personal, Indoor, and Mobile Radio Communications (PIMRC 2010), Sept. 2010,
Istanbul, Turke
The Three Node Wireless Network: Achievable Rates and Cooperation Strategies
We consider a wireless network composed of three nodes and limited by the
half-duplex and total power constraints. This formulation encompasses many of
the special cases studied in the literature and allows for capturing the common
features shared by them. Here, we focus on three special cases, namely 1) Relay
Channel, 2) Multicast Channel, and 3) Conference Channel. These special cases
are judicially chosen to reflect varying degrees of complexity while
highlighting the common ground shared by the different variants of the three
node wireless network. For the relay channel, we propose a new cooperation
scheme that exploits the wireless feedback gain. This scheme combines the
benefits of decode-and-forward and compress-and-forward strategies and avoids
the idealistic feedback assumption adopted in earlier works. Our analysis of
the achievable rate of this scheme reveals the diminishing feedback gain at
both the low and high signal-to-noise ratio regimes. Inspired by the proposed
feedback strategy, we identify a greedy cooperation framework applicable to
both the multicast and conference channels. Our performance analysis reveals
several nice properties of the proposed greedy approach and the central role of
cooperative source-channel coding in exploiting the receiver side information
in the wireless network setting. Our proofs for the cooperative multicast with
side-information rely on novel nested and independent binning encoders along
with a list decoder.Comment: 52 page
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