1,164 research outputs found
Self-concatenated code design and its application in power-efficient cooperative communications
In this tutorial, we have focused on the design of binary self-concatenated coding schemes with the help of EXtrinsic Information Transfer (EXIT) charts and Union bound analysis. The design methodology of future iteratively decoded self-concatenated aided cooperative communication schemes is presented. In doing so, we will identify the most important milestones in the area of channel coding, concatenated coding schemes and cooperative communication systems till date and suggest future research directions
STiCMAC: A MAC Protocol for Robust Space-Time Coding in Cooperative Wireless LANs
Relay-assisted cooperative wireless communication has been shown to have
significant performance gains over the legacy direct transmission scheme.
Compared with single relay based cooperation schemes, utilizing multiple relays
further improves the reliability and rate of transmissions. Distributed
space-time coding (DSTC), as one of the schemes to utilize multiple relays,
requires tight coordination between relays and does not perform well in a
distributed environment with mobility. In this paper, a cooperative medium
access control (MAC) layer protocol, called \emph{STiCMAC}, is designed to
allow multiple relays to transmit at the same time in an IEEE 802.11 network.
The transmission is based on a novel DSTC scheme called \emph{randomized
distributed space-time coding} (\emph{R-DSTC}), which requires minimum
coordination. Unlike conventional cooperation schemes that pick nodes with good
links, \emph{STiCMAC} picks a \emph{transmission mode} that could most improve
the end-to-end data rate. Any station that correctly receives from the source
can act as a relay and participate in forwarding. The MAC protocol is
implemented in a fully decentralized manner and is able to opportunistically
recruit relays on the fly, thus making it \emph{robust} to channel variations
and user mobility. Simulation results show that the network capacity and delay
performance are greatly improved, especially in a mobile environment.Comment: This paper is a revised version of a paper with the same name
submitted to IEEE Transaction on Wireless Communications. STiCMAC protocol
with RTS/CTS turned off is presented in the appendix of this draf
Cross-layer aided energy-efficient routing design for ad hoc networks
In this treatise, we first review some basic routing protocols conceived for ad hoc networks, followed by some design examples of cross-layer operation aided routing protocols. Specifically, cross-layer operation across the PHYsical layer (PHY), the Data Link layer (DL) and even the NETwork layer (NET) is exemplified for improving the energy efficiency of the entire system. Moreover, the philosophy of Opportunistic Routing (OR) is reviewed for the sake of further reducing the system's energy dissipation with the aid of optimized Power Allocation (PA). The system's end-to-end throughput is also considered in the context of a design example
Center for Aeronautics and Space Information Sciences
This report summarizes the research done during 1991/92 under the Center for Aeronautics and Space Information Science (CASIS) program. The topics covered are computer architecture, networking, and neural nets
Secure network coding with a cost criterion
Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 67-68).Network coding is a viable alterative to traditional routing methods that are being used in current data networks as it offers many advantages, including higher throughput rates and lower network costs. Although research has been conducted with regards to the cost and security issues of network coding, a joint investigation of these two parameters has not been done yet, thus providing the motivation for this thesis. For this thesis, we consider the situation where a set of messages is to be multicasted across the network, of which a known subset is of interest to a wiretapping adversary. The problem that we attempt to solve is to find a network coding scheme that has both a low network cost and a low probability of the wiretapper being able to retrieve all the messages of interest. We make use of random linear codes in anticipation for decentralized implementation of the scheme, and focus on the problem of finding the multicast subgraph. As an exact algorithmic solution is difficult, we propose two heuristic solutions, and compare their performances to traditional routing through a simulation study on Rocketfuel networks. Our results suggest that network coding can be more effective than routing for this low cost and secure data multicast problem, especially when the links are not easily tapped.by Jianlong Tan.M.Eng.and S.B
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