3,715 research outputs found
A Hybrid Instantaneous Recovery Route Design Scheme Using Different Coding-Aware Scenarios
ネットワーク上のサービスの進化と通信量の増加に従い、経済的で高信頼な経路の設計が求められている。本研究では、ネットワーク上の単一のリンク故障に対して、瞬時に復旧可能で、かつ,リソースを効率的に利用する経路設計法を扱う。1+1プロテクションは単一のリンク故障に対する瞬間復旧の代表的な手法である。このプロテクションでは同じデータが同時に独立の二つの経路へ送信されている。一つの経路上にシングルリンク故障が発生した時に着ノードで、もう一方の経路にスイッチすることによりデータが瞬時に復旧することが可能となる。この技術では必要な資源が少なくとも二倍以上必要となる。一方、ネットワーク符号化は中継ノードに到着データを符号化する技術がある。以前の研究で、この符号化の技術を用いて1+1プロテクションの瞬間復旧機能を保ちながら必要な資源を削減する方式として,TS (traffic splitting)と2SD (2 sources common destination)というシナリオが報告されている。本研究ではネットワーク上のすべて発着ノードのペアに対する1+1プロテクションを提供するハイブリッド経路設計法を提案する。この設計法は2段階のフェーズから構成される。第1フェーズでは、TSと2SDの選択肢の中から、それぞれの発着ノードペアに対して適切なプロテクションシナリオを選択する。第2フェーズでは、第1フェーズで得られた結果からシナリオの組み合わせが符号化可能な共通経路を抽出し、ネットワークコストが低減されるように最適な組み合わせを探索する。提案したハイブリッド経路設計法と、従来方法のTSと2SDとの性能を比較した結果、提案方法は,従来方法と比較して5%の資源を削減ができることを示す。電気通信大学201
Energy Efficient Survivable IP over WDM Networks with Network Coding
In this work we investigate the use of network coding in 1+1 survivable IP over WDM networks by encoding the protection paths of multiple flow with each other at intermediate nodes. We study the energy efficiency of this scheme through MILP, and a heuristic with five operating options. We evaluate the MILP and the heuristics on typical and regular network topologies. Our results show that implementing network coding can produce savings up to 37% on the ring topology and 23% considering typical topologies. We also study the impact of varying the demand volumes on the network coding performanc
On the benefits of Cross Layer Feedback in Multi-hop Wireless Networks
Wireless networks operate under harsh and time-varying channel conditions.
In wireless networks the time varying channel conditions lead to variable SINR and high BER.
The wireless channel is
distinct from and more unpredictable than the far more reliable wireline channel.
{\em Cross layer feedback} is a mechanism where layers provide {\em selective} information to other
layers to boost the performance of wireless networks.
{\em Cross layer feedback} can lead to a tremendous increase in the performance
of the TCP/IP stack in wireless networks, and an increase in the user's satisfaction level.
However, it is possible that naive feedbacks (or optimizations) can work non-coherently;
therefore, these can negatively effect the performance of the TCP/IP stack. In this paper, we holistically analyze
each layer of the TCP/IP stack, and propose possible Cross layer feedbacks which work coherently. The proposed Cross layer
feedbacks can greatly enhance the performance of the TCP/IP stack in wireless networks
Instantly Decodable Network Coding: From Centralized to Device-to-Device Communications
From its introduction to its quindecennial, network coding has built a strong reputation for enhancing packet recovery and achieving maximum information flow in both wired and wireless networks. Traditional studies focused on optimizing the throughput of the system by proposing elaborate schemes able to reach the network capacity. With the shift toward distributed computing on mobile devices, performance and complexity become both critical factors that affect the efficiency of a coding strategy. Instantly decodable network coding presents itself as a new paradigm in network coding that trades off these two aspects. This paper review instantly decodable network coding schemes by identifying, categorizing, and evaluating various algorithms proposed in the literature. The first part of the manuscript investigates the conventional centralized systems, in which all decisions are carried out by a central unit, e.g., a base-station. In particular, two successful approaches known as the strict and generalized instantly decodable network are compared in terms of reliability, performance, complexity, and packet selection methodology. The second part considers the use of instantly decodable codes in a device-to-device communication network, in which devices speed up the recovery of the missing packets by exchanging network coded packets. Although the performance improvements are directly proportional to the computational complexity increases, numerous successful schemes from both the performance and complexity viewpoints are identified
Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)
Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression
Progressively communicating rich telemetry from autonomous underwater vehicles via relays
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2012As analysis of imagery and environmental data plays a greater role in mission construction
and execution, there is an increasing need for autonomous marine vehicles
to transmit this data to the surface. Without access to the data acquired by a
vehicle, surface operators cannot fully understand the state of the mission. Communicating
imagery and high-resolution sensor readings to surface observers remains
a significant challenge – as a result, current telemetry from free-roaming
autonomous marine vehicles remains limited to ‘heartbeat’ status messages, with
minimal scientific data available until after recovery. Increasing the challenge, longdistance
communication may require relaying data across multiple acoustic hops
between vehicles, yet fixed infrastructure is not always appropriate or possible.
In this thesis I present an analysis of the unique considerations facing telemetry
systems for free-roaming Autonomous Underwater Vehicles (AUVs) used in exploration.
These considerations include high-cost vehicle nodes with persistent storage
and significant computation capabilities, combined with human surface operators
monitoring each node. I then propose mechanisms for interactive, progressive
communication of data across multiple acoustic hops. These mechanisms include
wavelet-based embedded coding methods, and a novel image compression scheme
based on texture classification and synthesis. The specific characteristics of underwater
communication channels, including high latency, intermittent communication,
the lack of instantaneous end-to-end connectivity, and a broadcast medium,
inform these proposals. Human feedback is incorporated by allowing operators to
identify segments of data thatwarrant higher quality refinement, ensuring efficient
use of limited throughput. I then analyze the performance of these mechanisms
relative to current practices.
Finally, I present CAPTURE, a telemetry architecture that builds on this analysis.
CAPTURE draws on advances in compression and delay tolerant networking to
enable progressive transmission of scientific data, including imagery, across multiple acoustic hops. In concert with a physical layer, CAPTURE provides an endto-
end networking solution for communicating science data from autonomous marine
vehicles. Automatically selected imagery, sonar, and time-series sensor data
are progressively transmitted across multiple hops to surface operators. Human
operators can request arbitrarily high-quality refinement of any resource, up to an
error-free reconstruction. The components of this system are then demonstrated
through three field trials in diverse environments on SeaBED, OceanServer and
Bluefin AUVs, each in different software architectures.Thanks to the National Science Foundation, and the
National Oceanic and Atmospheric Administration for
their funding of my education and this work
Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View
Small satellite systems enable whole new class of missions for navigation,
communications, remote sensing and scientific research for both civilian and
military purposes. As individual spacecraft are limited by the size, mass and
power constraints, mass-produced small satellites in large constellations or
clusters could be useful in many science missions such as gravity mapping,
tracking of forest fires, finding water resources, etc. Constellation of
satellites provide improved spatial and temporal resolution of the target.
Small satellite constellations contribute innovative applications by replacing
a single asset with several very capable spacecraft which opens the door to new
applications. With increasing levels of autonomy, there will be a need for
remote communication networks to enable communication between spacecraft. These
space based networks will need to configure and maintain dynamic routes, manage
intermediate nodes, and reconfigure themselves to achieve mission objectives.
Hence, inter-satellite communication is a key aspect when satellites fly in
formation. In this paper, we present the various researches being conducted in
the small satellite community for implementing inter-satellite communications
based on the Open System Interconnection (OSI) model. This paper also reviews
the various design parameters applicable to the first three layers of the OSI
model, i.e., physical, data link and network layer. Based on the survey, we
also present a comprehensive list of design parameters useful for achieving
inter-satellite communications for multiple small satellite missions. Specific
topics include proposed solutions for some of the challenges faced by small
satellite systems, enabling operations using a network of small satellites, and
some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications
Surveys and Tutorial
IoT for measurements and measurements for IoT
The thesis is framed in the broad strand of the Internet of Things, providing two parallel paths. On one hand, it deals with the identification of operational scenarios in which the IoT paradigm could be innovative and preferable to pre-existing solutions, discussing in detail a couple of applications. On the other hand, the thesis presents methodologies to assess the performance of technologies and related enabling protocols for IoT systems, focusing mainly on metrics and parameters related to the functioning of the physical layer of the systems
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