880 research outputs found
Robotic Wireless Sensor Networks
In this chapter, we present a literature survey of an emerging, cutting-edge,
and multi-disciplinary field of research at the intersection of Robotics and
Wireless Sensor Networks (WSN) which we refer to as Robotic Wireless Sensor
Networks (RWSN). We define a RWSN as an autonomous networked multi-robot system
that aims to achieve certain sensing goals while meeting and maintaining
certain communication performance requirements, through cooperative control,
learning and adaptation. While both of the component areas, i.e., Robotics and
WSN, are very well-known and well-explored, there exist a whole set of new
opportunities and research directions at the intersection of these two fields
which are relatively or even completely unexplored. One such example would be
the use of a set of robotic routers to set up a temporary communication path
between a sender and a receiver that uses the controlled mobility to the
advantage of packet routing. We find that there exist only a limited number of
articles to be directly categorized as RWSN related works whereas there exist a
range of articles in the robotics and the WSN literature that are also relevant
to this new field of research. To connect the dots, we first identify the core
problems and research trends related to RWSN such as connectivity,
localization, routing, and robust flow of information. Next, we classify the
existing research on RWSN as well as the relevant state-of-the-arts from
robotics and WSN community according to the problems and trends identified in
the first step. Lastly, we analyze what is missing in the existing literature,
and identify topics that require more research attention in the future
New Fault Tolerant Multicast Routing Techniques to Enhance Distributed-Memory Systems Performance
Distributed-memory systems are a key to achieve high performance computing and the most favorable architectures used in advanced research problems. Mesh connected multicomputer are one of the most popular architectures that have been implemented in many distributed-memory systems. These systems must support communication operations efficiently to achieve good performance. The wormhole switching technique has been widely used in design of distributed-memory systems in which the packet is divided into small flits. Also, the multicast communication has been widely used in distributed-memory systems which is one source node sends the same message to several destination nodes. Fault tolerance refers to the ability of the system to operate correctly in the presence of faults. Development of fault tolerant multicast routing algorithms in 2D mesh networks is an important issue. This dissertation presents, new fault tolerant multicast routing algorithms for distributed-memory systems performance using wormhole routed 2D mesh. These algorithms are described for fault tolerant routing in 2D mesh networks, but it can also be extended to other topologies. These algorithms are a combination of a unicast-based multicast algorithm and tree-based multicast algorithms. These algorithms works effectively for the most commonly encountered faults in mesh networks, f-rings, f-chains and concave fault regions. It is shown that the proposed routing algorithms are effective even in the presence of a large number of fault regions and large size of fault region. These algorithms are proved to be deadlock-free. Also, the problem of fault regions overlap is solved. Four essential performance metrics in mesh networks will be considered and calculated; also these algorithms are a limited-global-information-based multicasting which is a compromise of local-information-based approach and global-information-based approach. Data mining is used to validate the results and to enlarge the sample. The proposed new multicast routing techniques are used to enhance the performance of distributed-memory systems. Simulation results are presented to demonstrate the efficiency of the proposed algorithms
Secure Group Communication in Delay Tolerant Mobile Ad-Hoc Network
Delay-tolerant networks (DTNs) are well-known for delivering various types of information from different senders in a multicast manner, both in centralised and decentralised networks. Wireless mobile nodes form small networks in which one or more senders transmit data to one or more destinations through intermediate nodes. DTN routing protocols differ from traditional wireless routing protocols. There are security threats in DTNs, such as blackhole attackers dropping data, jamming attacks consuming bandwidth, and Vampire attacks depleting battery power and available bandwidth. This paper proposes a prevention scheme to detect and mitigate all three types of attackers in multicast communication. These attackers can impact performance by generating false replies, flooding with redundant information, and wasting communication power. The primary focus of this paper is on security issues related to DTN routing protocols. In order to counter malicious nodes, a blacklist is maintained, and if a neighbour identifies a node as malicious, it excludes packets from that node. Meanwhile, the neighbour continues sending packets to the malicious node, except for broadcast packets, which are dropped. If a node is found to forward no packets or only some packets by all its neighbours, any reply it gives to route requests is disregarded, and any request it initiates is ignored. Successful data reception at the destination indicates that hop-based data delivery maintains a record of successful transmissions. The proposed security scheme demonstrates improved performance
A survey of flooding, gossip routing, and related schemes for wireless multi- hop networks
Flooding is an essential and critical service in computer networks that is
used by many routing protocols to send packets from a source to all nodes in
the network. As the packets are forwarded once by each receiving node, many
copies of the same packet traverse the network which leads to high redundancy
and unnecessary usage of the sparse capacity of the transmission medium.
Gossip routing is a well-known approach to improve the flooding in wireless
multi-hop networks. Each node has a forwarding probability p that is either
statically per-configured or determined by information that is available at
runtime, e.g, the node degree. When a packet is received, the node selects a
random number r. If the number r is below p, the packet is forwarded and
otherwise, in the most simple gossip routing protocol, dropped. With this
approach the redundancy can be reduced while at the same time the reachability
is preserved if the value of the parameter p (and others) is chosen with
consideration of the network topology. This technical report gives an overview
of the relevant publications in the research domain of gossip routing and
gives an insight in the improvements that can be achieved. We discuss the
simulation setups and results of gossip routing protocols as well as further
improved flooding schemes. The three most important metrics in this
application domain are elaborated: reachability, redundancy, and management
overhead. The published studies used simulation environments for their
research and thus the assumptions, models, and parameters of the simulations
are discussed and the feasibility of an application for real world wireless
networks are highlighted. Wireless mesh networks based on IEEE 802.11 are the
focus of this survey but publications about other network types and
technologies are also included. As percolation theory, epidemiological models,
and delay tolerant networks are often referred as foundation, inspiration, or
application of gossip routing in wireless networks, a brief introduction to
each research domain is included and the applicability of the particular
models for the gossip routing is discussed
A Survey on Wireless Sensor Network Security
Wireless sensor networks (WSNs) have recently attracted a lot of interest in
the research community due their wide range of applications. Due to distributed
nature of these networks and their deployment in remote areas, these networks
are vulnerable to numerous security threats that can adversely affect their
proper functioning. This problem is more critical if the network is deployed
for some mission-critical applications such as in a tactical battlefield.
Random failure of nodes is also very likely in real-life deployment scenarios.
Due to resource constraints in the sensor nodes, traditional security
mechanisms with large overhead of computation and communication are infeasible
in WSNs. Security in sensor networks is, therefore, a particularly challenging
task. This paper discusses the current state of the art in security mechanisms
for WSNs. Various types of attacks are discussed and their countermeasures
presented. A brief discussion on the future direction of research in WSN
security is also included.Comment: 24 pages, 4 figures, 2 table
Scalable Schedule-Aware Bundle Routing
This thesis introduces approaches providing scalable delay-/disruption-tolerant routing capabilities in scheduled space topologies. The solution is developed for the requirements derived from use cases built according to predictions for future space topology, like the future Mars communications architecture report from the interagency operations advisory group. A novel routing algorithm is depicted to provide optimized networking performance that discards the scalability issues inherent to state-of-the-art approaches. This thesis also proposes a new recommendation to render volume management concerns generic and easily exchangeable, including a new simple management technique increasing volume awareness accuracy while being adaptable to more particular use cases. Additionally, this thesis introduces a more robust and scalable approach for internetworking between subnetworks to increase the throughput, reduce delays, and ease configuration thanks to its high flexibility.:1 Introduction
1.1 Motivation
1.2 Problem statement
1.3 Objectives
1.4 Outline
2 Requirements
2.1 Use cases
2.2 Requirements
2.2.1 Requirement analysis
2.2.2 Requirements relative to the routing algorithm
2.2.3 Requirements relative to the volume management
2.2.4 Requirements relative to interregional routing
3 Fundamentals
3.1 Delay-/disruption-tolerant networking
3.1.1 Architecture
3.1.2 Opportunistic and deterministic DTNs
3.1.3 DTN routing
3.1.4 Contact plans
3.1.5 Volume management
3.1.6 Regions
3.2 Contact graph routing
3.2.1 A non-replication routing scheme
3.2.2 Route construction
3.2.3 Route selection
3.2.4 Enhancements and main features
3.3 Graph theory and DTN routing
3.3.1 Mapping with DTN objects
3.3.2 Shortest path algorithm
3.3.3 Edge and vertex contraction
3.4 Algorithmic determinism and predictability
4 Preliminary analysis
4.1 Node and contact graphs
4.2 Scenario
4.3 Route construction in ION-CGR
4.4 Alternative route search
4.4.1 Yen’s algorithm scalability
4.4.2 Blocking issues with Yen
4.4.3 Limiting contact approaches
4.5 CGR-multicast and shortest-path tree search
4.6 Volume management
4.6.1 Volume obstruction
4.6.2 Contact sink
4.6.3 Ghost queue
4.6.4 Data rate variations
4.7 Hierarchical interregional routing
4.8 Other potential issues
5 State-of-the-art and related work
5.1 Taxonomy
5.2 Opportunistic and probabilistic approaches
5.2.1 Flooding approaches
5.2.2 PROPHET
5.2.3 MaxProp
5.2.4 Issues
5.3 Deterministic approaches
5.3.1 Movement-aware routing over interplanetary networks
5.3.2 Delay-tolerant link state routing
5.3.3 DTN routing for quasi-deterministic networks
5.3.4 Issues
5.4 CGR variants and enhancements
5.4.1 CGR alternative routing table computation
5.4.2 CGR-multicast
5.4.3 CGR extensions
5.4.4 RUCoP and CGR-hop
5.4.5 Issues
5.5 Interregional routing
5.5.1 Border gateway protocol
5.5.2 Hierarchical interregional routing
5.5.3 Issues
5.6 Further approaches
5.6.1 Machine learning approaches
5.6.2 Tropical geometry
6 Scalable schedule-aware bundle routing
6.1 Overview
6.2 Shortest-path tree routing for space networks
6.2.1 Structure
6.2.2 Tree construction
6.2.3 Tree management
6.2.4 Tree caching
6.3 Contact segmentation
6.3.1 Volume management interface
6.3.2 Simple volume manager
6.3.3 Enhanced volume manager
6.4 Contact passageways
6.4.1 Regional border definition
6.4.2 Virtual nodes
6.4.3 Pathfinding and administration
7 Evaluation
7.1 Methodology
7.1.1 Simulation tools
7.1.2 Simulator extensions
7.1.3 Algorithms and scenarios
7.2 Offline analysis
7.3 Eliminatory processing pressures
7.4 Networking performance
7.4.1 Intraregional unicast routing tests
7.4.2 Intraregional multicast tests
7.4.3 Interregional routing tests
7.4.4 Behavior with congestion
7.5 Requirement fulfillment
8 Summary and Outlook
8.1 Conclusion
8.2 Future works
8.2.1 Next development steps
8.2.2 Contact graph routin
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On Multicast in Asynchronous Networks-on-Chip: Techniques, Architectures, and FPGA Implementation
In this era of exascale computing, conventional synchronous design techniques are facing unprecedented challenges. The consumer electronics market is replete with many-core systems in the range of 16 cores to thousands of cores on chip, integrating multi-billion transistors. However, with this ever increasing complexity, the traditional design approaches are facing key issues such as increasing chip power, process variability, aging, thermal problems, and scalability. An alternative paradigm that has gained significant interest in the last decade is asynchronous design. Asynchronous designs have several potential advantages: they are naturally energy proportional, burning power only when active, do not require complex clock distribution, are robust to different forms of variability, and provide ease of composability for heterogeneous platforms. Networks-on-chip (NoCs) is an interconnect paradigm that has been introduced to deal with the ever-increasing system complexity. NoCs provide a distributed, scalable, and efficient interconnect solution for today’s many-core systems. Moreover, NoCs are a natural match with asynchronous design techniques, as they separate communication infrastructure and timing from the computational elements. To this end, globally-asynchronous locally-synchronous (GALS) systems that interconnect multiple processing cores, operating at different clock speeds, using an asynchronous NoC, have gained significant interest. While asynchronous NoCs have several advantages, they also face a key challenge of supporting new types of traffic patterns. Once such pattern is multicast communication, where a source sends packets to arbitrary number of destinations. Multicast is not only common in parallel computing, such as for cache coherency, but also for emerging areas such as neuromorphic computing. This important capability has been largely missing from asynchronous NoCs. This thesis introduces several efficient multicast solutions for these interconnects. In particular, techniques, and network architectures are introduced to support high-performance and low-power multicast. Two leading network topologies are the focus: a variant mesh-of-trees (MoT) and a 2D mesh. In addition, for a more realistic implementation and analysis, as well as significantly advancing the field of asynchronous NoCs, this thesis also targets synthesis of these NoCs on commercial FPGAs. While there has been significant advances in FPGA technologies, there has been only limited research on implementing asynchronous NoCs on FPGAs. To this end, a systematic computeraided design (CAD) methodology has been introduced to efficiently and safely map asynchronous NoCs on FPGAs. Overall, this thesis makes the following three contributions. The first contribution is a multicast solution for a variant MoT network topology. This topology consists of simple low-radix switches, and has been used in high-performance computing platforms. A novel local speculation technique is introduced, where a subset of the network’s switches are speculative that always broadcast every packet. These switches are very simple and have high performance. Speculative switches are surrounded by non-speculative ones that route packets based on their destinations and also throttle any redundant copies created by the former. This hybrid network architecture achieved significant performance and power benefits over other multicast approaches. The second contribution is a multicast solution for a 2D-mesh topology, which is more complex with higher-radix switches and also is more commonly used. A novel continuous-time replication strategy is introduced to optimize the critical multi-way forking operation of a multicast transmission. In this technique, a multicast packet is first stored in an input port of a switch, from where it is sent through distinct output ports towards different destinations concurrently, at each output’s own rate and in continuous time. This strategy is shown to have significant latency and energy benefits over an approach that performs multicast using multiple distinct serial unicasts to each destination. Finally, a systematic CAD methodology is introduced to synthesize asynchronous NoCs on commercial FPGAs. A two-fold goal is targeted: correctness and high performance. For ease of implementation, only existing FPGA synthesis tools are used. Moreover, since asynchronous NoCs involve special asynchronous components, a comprehensive guide is introduced to map these elements correctly and efficiently. Two asynchronous NoC switches are synthesized using the proposed approach on a leading Xilinx FPGA in 28 nm: one that only handles unicast, and the other that also supports multicast. Both showed significant energy benefits with some performance gains over a state-of-the-art synchronous switch
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