10,175 research outputs found
Rate Aware Instantly Decodable Network Codes
This paper addresses the problem of reducing the delivery time of data
messages to cellular users using instantly decodable network coding (IDNC) with
physical-layer rate awareness. While most of the existing literature on IDNC
does not consider any physical layer complications and abstract the model as
equally slotted time for all users, this paper proposes a cross-layer scheme
that incorporates the different channel rates of the various users in the
decision process of both the transmitted message combinations and the rates
with which they are transmitted. The consideration of asymmetric rates for
receivers reflects more practical application scenarios and introduces a new
trade-off between the choice of coding combinations for various receivers and
the broadcasting rate for achieving shorter completion time. The completion
time minimization problem in such scenario is first shown to be intractable.
The problem is, thus, approximated by reducing, at each transmission, the
increase of an anticipated version of the completion time. The paper solves the
problem by formulating it as a maximum weight clique problem over a newly
designed rate aware IDNC (RA-IDNC) graph. The highest weight clique in the
created graph being potentially not unique, the paper further suggests a
multi-layer version of the proposed solution to improve the obtained results
from the employed completion time approximation. Simulation results indicate
that the cross-layer design largely outperforms the uncoded transmissions
strategies and the classical IDNC scheme
Secrecy Wireless Information and Power Transfer in Fading Wiretap Channel
Simultaneous wireless information and power transfer (SWIPT) has recently
drawn significant interests for its dual use of radio signals to provide
wireless data and energy access at the same time. However, a challenging
secrecy communication issue arises as the messages sent to the information
receivers (IRs) may be eavesdropped by the energy receivers (ERs), which are
presumed to harvest energy only from the received signals. To tackle this
problem, we propose in this paper an artificial noise (AN) aided transmission
scheme to facilitate the secrecy information transmission to IRs and yet meet
the energy harvesting requirement for ERs, under the assumption that the AN can
be cancelled at IRs but not at ERs. Specifically, the proposed scheme splits
the transmit power into two parts, to send the confidential message to the IR
and an AN to interfere with the ER, respectively. Under a simplified three-node
wiretap channel setup, the transmit power allocations and power splitting
ratios over fading channels are jointly optimized to minimize the outage
probability for delay-limited secrecy information transmission, or to maximize
the average rate for no-delay-limited secrecy information transmission, subject
to a combination of average and peak power constraints at the transmitter as
well as an average energy harvesting constraint at the ER. Both the secrecy
outage probability minimization and average rate maximization problems are
shown to be non-convex, for each of which we propose the optimal solution based
on the dual decomposition as well as suboptimal solution based on the
alternating optimization. Furthermore, two benchmark schemes are introduced for
comparison. Finally, the performances of proposed schemes are evaluated by
simulations in terms of various trade-offs for wireless (secrecy) information
versus energy transmissions.Comment: to appear in IEEE Transactions on Vehicular Technolog
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