符号化可能なネットワークにおける高信頼経路設計方式

電気通信大学201

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

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

Recent Trends in Communication Networks

In recent years there has been many developments in communication technology. This has greatly enhanced the computing power of small handheld resource-constrained mobile devices. Different generations of communication technology have evolved. This had led to new research for communication of large volumes of data in different transmission media and the design of different communication protocols. Another direction of research concerns the secure and error-free communication between the sender and receiver despite the risk of the presence of an eavesdropper. For the communication requirement of a huge amount of multimedia streaming data, a lot of research has been carried out in the design of proper overlay networks. The book addresses new research techniques that have evolved to handle these challenges

Enhanced Rateless Coding and Compressive Sensing for Efficient Data/multimedia Transmission and Storage in Ad-hoc and Sensor Networks

In this dissertation, we investigate the theory and applications of the novel class of FEC codes called rateless or fountain codes in video transmission and wireless sensor networks (WSN). First, we investigate the rateless codes in intermediate region where the number of received encoded symbols is less that minimum required for full datablock decoding. We devise techniques to improve the input symbol recovery rate when the erasure rate is unknown, and also for the case where an estimate of the channel erasure rate is available. Further, we design unequal error protection (UEP) rateless codes for distributed data collection of data blocks of unequal lengths, where two encoders send their rateless coded output symbols to a destination through a common relay. We design such distributed rateless codes, and jointly optimize rateless coding parameters at each nodes and relaying parameters. Moreover, we investigate the performance of rateless codes with finite block length in the presence of feedback channel. We propose a smart feedback generation technique that greatly improves the performance of rateless codes when data block is finite. Moreover, we investigate the applications of UEP-rateless codes in video transmission systems. Next, we study the optimal cross-layer design of a video transmission system with rateless coding at application layer and fixed-rate coding (RCPC coding) at physical layer. Finally, we review the emerging compressive sensing (CS) techniques that have close connections to FEC coding theory, and designed an efficient data storage algorithm for WSNs employing CS referred to by CStorage. First, we propose to employ probabilistic broadcasting (PB) to form one CS measurement at each node and design CStorage- P. Later, we can query any arbitrary small subset of nodes and recover all sensors reading. Next, we design a novel parameterless and more efficient data dissemination algorithm that uses two-hop neighbor information referred to alternating branches (AB).We replace PB with AB and design CStorage-B, which results in a lower number of transmissions compared to CStorage-P.Electrical Engineerin

A hybrid packet loss recovery technique in wireless ad hoc networks

TCP utilization in wireless networks poses certain problems due to its inability to distinguish packet losses caused by congestion from those caused by frequent wireless errors, leading to degraded network performance. To avoid these problems and to minimize the effect of intensive channel contention in wireless networks, this work presents a new Hybrid ARQ technique for reliable and efficient packets transfer in static wireless ad hoc network. It is a combination of recent FEC based Raptor coding technique with ARQ based selective retransmission method, which outperforms purely ARQ based method. In contrast to most Hybrid ARQ techniques, which usually employ a byte level FEC, we mostly use packet level FEC in our simulations for the data transfer, on top of less frequent ARQ to recover the residual errors. Existing packet level FEC methods are mostly based on simple parity check codes or Reed Solomon codes with erasure decoding; in this work we use the recent raptor codes. We also introduce the notion of adaptive redundancy which helps to achieve better average network performance and to further improve the redundancy efficiency

Adaptive Communication for Mobile Multi-Robot Systems

Mobile multi-robot systems can be immensely powerful, serving as force multipliers for human operators in search-and-rescue operations, urban reconnaissance missions, and more. Key to fulfilling this potential is robust communication, which allows robots to share sensor data or inform others of their intentions. However, wireless communication is often unreliable for mobile multi-robot systems, exhibiting losses, delays, and outages as robots move through their environment. Furthermore, the wireless communication spectrum is a shared resource, and multi-robot systems must determine how to use its limited bandwidth in accomplishing their missions. This dissertation addresses the challenges of inter-robot communication in two thrusts. In the first thrust, we improve the reliability of such communication through the application of a technique we call Adaptive Erasure Coding (AEC). Erasure codes enable recovery from packet loss through the use of redundancy. Conditions in a mobile robotic network are continually changing, so AEC varies the amount of redundancy applied to achieve a probabilistic delivery guarantee. In the second thrust, we describe a mechanism by which robots can make communication decisions by considering the expected effect of a proposed communication action on team performance. We call this algorithm Optimizing Communication under Bandwidth Constraints (OCBC). Given a finite amount of available bandwidth, OCBC optimizes the contents of a message to respect the bandwidth constraint.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/149815/1/ryanjmar_1.pd

Network Coding Applications

Network coding is an elegant and novel technique introduced at the turn of the millennium to improve network throughput and performance. It is expected to be a critical technology for networks of the future. This tutorial deals with wireless and content distribution networks, considered to be the most likely applications of network coding, and it also reviews emerging applications of network coding such as network monitoring and management. Multiple unicasts, security, networks with unreliable links, and quantum networks are also addressed. The preceding companion deals with theoretical foundations of network coding