31,895 research outputs found
Secure on-off transmission design with channel estimation errors
Physical layer security has recently been regarded
as an emerging technique to complement and improve the
communication security in future wireless networks. The current
research and development in physical layer security are often
based on the ideal assumption of perfect channel knowledge or
the capability of variable-rate transmissions. In this paper, we
study the secure transmission design in more practical scenarios
by considering channel estimation errors at the receiver and
investigating both fixed-rate and variable-rate transmissions.
Assuming quasi-static fading channels, we design secure on-off
transmission schemes to maximize the throughput subject to
a constraint on secrecy outage probability. For systems with
given and fixed encoding rates, we show how the optimal on-off
transmission thresholds and the achievable throughput vary with
the amount of knowledge on the eavesdropper’s channel. In
particular, our design covers the interesting case where the
eavesdropper also uses the pilots sent from the transmitter to
obtain imperfect channel estimation. An interesting observation
is that using too much pilot power can harm the throughput
of secure transmission if both the legitimate receiver and the
eavesdropper have channel estimation errors, while the secure
transmission always benefits from increasing pilot power when
only the legitimate receiver has channel estimation errors but
not the eavesdropper. When the encoding rates are controllable
parameters to design, we further derive both a non-adaptive
and an adaptive rate transmission schemes by jointly optimizing
the encoding rates and the on-off transmission thresholds to
maximize the throughput of secure transmissions
Channel-based key generation for encrypted body-worn wireless sensor networks
Body-worn sensor networks are important for rescue-workers, medical and many other applications. Sensitive data are often transmitted over such a network, motivating the need for encryption. Body-worn sensor networks are deployed in conditions where the wireless communication channel varies dramatically due to fading and shadowing, which is considered a disadvantage for communication. Interestingly, these channel variations can be employed to extract a common encryption key at both sides of the link. Legitimate users share a unique physical channel and the variations thereof provide data series on both sides of the link, with highly correlated values. An eavesdropper, however, does not share this physical channel and cannot extract the same information when intercepting the signals. This paper documents a practical wearable communication system implementing channel-based key generation, including an implementation and a measurement campaign comprising indoor as well as outdoor measurements. The results provide insight into the performance of channel-based key generation in realistic practical conditions. Employing a process known as key reconciliation, error free keys are generated in all tested scenarios. The key-generation system is computationally simple and therefore compatible with the low-power micro controllers and low-data rate transmissions commonly used in wireless sensor networks
Artificial-Noise-Aided Secure Multi-Antenna Transmission with Limited Feedback
We present an optimized secure multi-antenna transmission approach based on
artificial-noise-aided beamforming, with limited feedback from a desired
single-antenna receiver. To deal with beamformer quantization errors as well as
unknown eavesdropper channel characteristics, our approach is aimed at
maximizing throughput under dual performance constraints - a connection outage
constraint on the desired communication channel and a secrecy outage constraint
to guard against eavesdropping. We propose an adaptive transmission strategy
that judiciously selects the wiretap coding parameters, as well as the power
allocation between the artificial noise and the information signal. This
optimized solution reveals several important differences with respect to
solutions designed previously under the assumption of perfect feedback. We also
investigate the problem of how to most efficiently utilize the feedback bits.
The simulation results indicate that a good design strategy is to use
approximately 20% of these bits to quantize the channel gain information, with
the remainder to quantize the channel direction, and this allocation is largely
insensitive to the secrecy outage constraint imposed. In addition, we find that
8 feedback bits per transmit antenna is sufficient to achieve approximately 90%
of the throughput attainable with perfect feedback.Comment: to appear in IEEE Transactions on Wireless Communication
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