1,280 research outputs found
Secrecy Through Synchronization Errors
In this paper, we propose a transmission scheme that achieves information
theoretic security, without making assumptions on the eavesdropper's channel.
This is achieved by a transmitter that deliberately introduces synchronization
errors (insertions and/or deletions) based on a shared source of randomness.
The intended receiver, having access to the same shared source of randomness as
the transmitter, can resynchronize the received sequence. On the other hand,
the eavesdropper's channel remains a synchronization error channel. We prove a
secrecy capacity theorem, provide a lower bound on the secrecy capacity, and
propose numerical methods to evaluate it.Comment: 5 pages, 6 figures, submitted to ISIT 201
Compressive Sensing for Feedback Reduction in MIMO Broadcast Channels
We propose a generalized feedback model and compressive sensing based
opportunistic feedback schemes for feedback resource reduction in MIMO
Broadcast Channels under the assumption that both uplink and downlink channels
undergo block Rayleigh fading. Feedback resources are shared and are
opportunistically accessed by users who are strong, i.e. users whose channel
quality information is above a certain fixed threshold. Strong users send same
feedback information on all shared channels. They are identified by the base
station via compressive sensing. Both analog and digital feedbacks are
considered. The proposed analog & digital opportunistic feedback schemes are
shown to achieve the same sum-rate throughput as that achieved by dedicated
feedback schemes, but with feedback channels growing only logarithmically with
number of users. Moreover, there is also a reduction in the feedback load. In
the analog feedback case, we show that the propose scheme reduces the feedback
noise which eventually results in better throughput, whereas in the digital
feedback case the proposed scheme in a noisy scenario achieves almost the
throughput obtained in a noiseless dedicated feedback scenario. We also show
that for a fixed given budget of feedback bits, there exist a trade-off between
the number of shared channels and thresholds accuracy of the feedback SINR.Comment: Submitted to IEEE Transactions on Wireless Communications, April 200
Multigroup Synchronization in 1D-Bernoulli Chaotic Collaborative CDMA
Code-division multiple access (CDMA) has played a remarkable role in the field of wireless communication systems, and its capacity and security requirements are still being addressed. Collaborative multiuser transmission and detection are a contemporary technique used in CDMA systems. The performance of these systems is governed by the proper accommodation of the users and by proper synchronization schemes. The major research concerns in the existing multiuser overloaded CDMA schemes are (i) statistically uncorrelated PN sequences that cause multiple-access interference (MAI) and (ii) the security of the user's data. In this paper, a novel grouped CDMA scheme, the 1D-Bernoulli chaotic collaborative CDMA (BCC-CDMA), is introduced, in which mutually orthogonal chaotic sequences spread the users' data within a group. The synchronization of multiple groups in this scheme has been analyzed under MAI limited environments and the results are presented. This increases the user capacity and also provides sufficient security as a result of the correlation properties possessed by the chaotic codes. Multigroup synchronization is achieved using a 1D chaotic pilot sequence generated by the Bernoulli Map. The mathematical model of the proposed system is described and compared with the theoretical model of the synchronization in CDMA, the simulation results of which are presented
Database Matching Under Noisy Synchronization Errors
The re-identification or de-anonymization of users from anonymized data
through matching with publicly available correlated user data has raised
privacy concerns, leading to the complementary measure of obfuscation in
addition to anonymization. Recent research provides a fundamental understanding
of the conditions under which privacy attacks, in the form of database
matching, are successful in the presence of obfuscation. Motivated by
synchronization errors stemming from the sampling of time-indexed databases,
this paper presents a unified framework considering both obfuscation and
synchronization errors and investigates the matching of databases under noisy
entry repetitions. By investigating different structures for the repetition
pattern, replica detection and seeded deletion detection algorithms are devised
and sufficient and necessary conditions for successful matching are derived.
Finally, the impacts of some variations of the underlying assumptions, such as
the adversarial deletion model, seedless database matching, and zero-rate
regime, on the results are discussed. Overall, our results provide insights
into the privacy-preserving publication of anonymized and obfuscated
time-indexed data as well as the closely related problem of the capacity of
synchronization channels
Exact Classical Simulation of the GHZ Distribution
John Bell has shown that the correlations entailed by quantum
mechanics cannot be reproduced by a classical process involving
non-communicating parties. But can they be simulated with the help
of bounded communication? This problem has been studied for more
than twenty years and it is now well understood in the case of
bipartite entanglement. However, the issue was still widely open for
multipartite entanglement, even for the simplest case, which is
the tripartite Greenberger-Horne-Zeilinger (GHZ) state.
We give an exact simulation of arbitrary independent von Neumann
measurements on general n-partite GHZ states. Our protocol
requires O(n^2) bits of expected communication between the
parties, and O(n*log(n)) expected time is sufficient to carry it
out in parallel. Furthermore, we need only an expectation of
O(n) independent unbiased random bits, with no need for the
generation of continuous real random variables nor prior shared
random variables. In the case of equatorial measurements, we
improve earlier results with a protocol that needs only O(n*log(n)) bits of communication and O(log^2(n)) parallel time. At the
cost of a slight increase in the number of bits communicated, these
tasks can be accomplished with a constant expected number of rounds
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