1,803 research outputs found
On the Delay Advantage of Coding in Packet Erasure Networks
We consider the delay of network coding compared to routing with retransmissions in packet erasure networks with probabilistic erasures. We investigate the sublinear term in the block delay required for unicasting n packets and show that there is an unbounded gap between network coding and routing. In particular, we show that delay benefit of network coding scales at least as √n. Our analysis of the delay function for the routing strategy involves a major technical challenge of computing the expectation of the maximum of two negative binomial random variables. Previous characterizations of this expectation are approximate; we derive an exact characterization and analyze its scaling behavior, which may be of independent interest. We also use a martingale bounded differences argument to show that the actual coding delay is concentrated around its expectation
Random Linear Network Coding For Time Division Duplexing: Energy Analysis
We study the energy performance of random linear network coding for time
division duplexing channels. We assume a packet erasure channel with nodes that
cannot transmit and receive information simultaneously. The sender transmits
coded data packets back-to-back before stopping to wait for the receiver to
acknowledge the number of degrees of freedom, if any, that are required to
decode correctly the information. Our analysis shows that, in terms of mean
energy consumed, there is an optimal number of coded data packets to send
before stopping to listen. This number depends on the energy needed to transmit
each coded packet and the acknowledgment (ACK), probabilities of packet and ACK
erasure, and the number of degrees of freedom that the receiver requires to
decode the data. We show that its energy performance is superior to that of a
full-duplex system. We also study the performance of our scheme when the number
of coded packets is chosen to minimize the mean time to complete transmission
as in [1]. Energy performance under this optimization criterion is found to be
close to optimal, thus providing a good trade-off between energy and time
required to complete transmissions.Comment: 5 pages, 6 figures, Accepted to ICC 200
Centralized and Cooperative Transmission of Secure Multiple Unicasts using Network Coding
We introduce a method for securely delivering a set of messages to a group of
clients over a broadcast erasure channel where each client is interested in a
distinct message. Each client is able to obtain its own message but not the
others'. In the proposed method the messages are combined together using a
special variant of random linear network coding. Each client is provided with a
private set of decoding coefficients to decode its own message. Our method
provides security for the transmission sessions against computational
brute-force attacks and also weakly security in information theoretic sense. As
the broadcast channel is assumed to be erroneous, the missing coded packets
should be recovered in some way. We consider two different scenarios. In the
first scenario the missing packets are retransmitted by the base station
(centralized). In the second scenario the clients cooperate with each other by
exchanging packets (decentralized). In both scenarios, network coding
techniques are exploited to increase the total throughput. For the case of
centralized retransmissions we provide an analytical approximation for the
throughput performance of instantly decodable network coded (IDNC)
retransmissions as well as numerical experiments. For the decentralized
scenario, we propose a new IDNC based retransmission method where its
performance is evaluated via simulations and analytical approximation.
Application of this method is not limited to our special problem and can be
generalized to a new class of problems introduced in this paper as the
cooperative index coding problem
Rethinking the Intercept Probability of Random Linear Network Coding
This letter considers a network comprising a transmitter, which employs
random linear network coding to encode a message, a legitimate receiver, which
can recover the message if it gathers a sufficient number of linearly
independent coded packets, and an eavesdropper. Closed-form expressions for the
probability of the eavesdropper intercepting enough coded packets to recover
the message are derived. Transmission with and without feedback is studied.
Furthermore, an optimization model that minimizes the intercept probability
under delay and reliability constraints is presented. Results validate the
proposed analysis and quantify the secrecy gain offered by a feedback link from
the legitimate receiver.Comment: IEEE Communications Letters, to appea
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