15,504 research outputs found
Wireless industrial monitoring and control networks: the journey so far and the road ahead
While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks
Architectures and Key Technical Challenges for 5G Systems Incorporating Satellites
Satellite Communication systems are a promising solution to extend and
complement terrestrial networks in unserved or under-served areas. This aspect
is reflected by recent commercial and standardisation endeavours. In
particular, 3GPP recently initiated a Study Item for New Radio-based, i.e., 5G,
Non-Terrestrial Networks aimed at deploying satellite systems either as a
stand-alone solution or as an integration to terrestrial networks in mobile
broadband and machine-type communication scenarios. However, typical satellite
channel impairments, as large path losses, delays, and Doppler shifts, pose
severe challenges to the realisation of a satellite-based NR network. In this
paper, based on the architecture options currently being discussed in the
standardisation fora, we discuss and assess the impact of the satellite channel
characteristics on the physical and Medium Access Control layers, both in terms
of transmitted waveforms and procedures for enhanced Mobile BroadBand (eMBB)
and NarrowBand-Internet of Things (NB-IoT) applications. The proposed analysis
shows that the main technical challenges are related to the PHY/MAC procedures,
in particular Random Access (RA), Timing Advance (TA), and Hybrid Automatic
Repeat reQuest (HARQ) and, depending on the considered service and
architecture, different solutions are proposed.Comment: Submitted to Transactions on Vehicular Technologies, April 201
On modelling network coded ARQ-based channels
Network coding (NC) has been an attractive research topic in recent years as a means of offering a throughput improvement, especially in multicast scenarios. The throughput gain is achieved by introducing an algebraic method for combining multiple input streams of packets which are addressing one output port at an intermediate node. We present a practical implementation of network coding in conjunction with error control schemes, namely the Stop-and-Wait (SW) and Selective Repeat (SR) protocols. We propose a modified NC scheme and apply it at an intermediate SW ARQ-based link to reduce ARQ control
signals at each transmission. We further extend this work to investigate the usefulness of NC in the Butterfly multicast network which adopts the SR ARQ protocol as an error control scheme. We validate our throughput analysis using a relatively recent discrete-event simulator, SimEvents®. The results show that the proposed scheme offers a throughput advantage of at least 50% over traditional SW ARQ, and that this is particularly noticeable in the presence of high error rates. In the multicast network, however, simulation results show
that when compared with the traditional scheme, NC-SR ARQ can achieve a throughput gain of between 2% and 96% in a low bandwidth channel and up to 19% in a high bandwidth channel with errors
Energy-efficient wireless communication
In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters
To NACK or not to NACK? Negative Acknowledgments in Information-Centric Networking
Information-Centric Networking (ICN) is an internetworking paradigm that
offers an alternative to the current IP\nobreakdash-based Internet
architecture. ICN's most distinguishing feature is its emphasis on information
(content) instead of communication endpoints. One important open issue in ICN
is whether negative acknowledgments (NACKs) at the network layer are useful for
notifying downstream nodes about forwarding failures, or requests for incorrect
or non-existent information. In benign settings, NACKs are beneficial for ICN
architectures, such as CCNx and NDN, since they flush state in routers and
notify consumers. In terms of security, NACKs seem useful as they can help
mitigating so-called Interest Flooding attacks. However, as we show in this
paper, network-layer NACKs also have some unpleasant security implications. We
consider several types of NACKs and discuss their security design requirements
and implications. We also demonstrate that providing secure NACKs triggers the
threat of producer-bound flooding attacks. Although we discuss some potential
countermeasures to these attacks, the main conclusion of this paper is that
network-layer NACKs are best avoided, at least for security reasons.Comment: 10 pages, 7 figure
In-Order Delivery Delay of Transport Layer Coding
A large number of streaming applications use reliable transport protocols
such as TCP to deliver content over the Internet. However, head-of-line
blocking due to packet loss recovery can often result in unwanted behavior and
poor application layer performance. Transport layer coding can help mitigate
this issue by helping to recover from lost packets without waiting for
retransmissions. We consider the use of an on-line network code that inserts
coded packets at strategic locations within the underlying packet stream. If
retransmissions are necessary, additional coding packets are transmitted to
ensure the receiver's ability to decode. An analysis of this scheme is provided
that helps determine both the expected in-order packet delivery delay and its
variance. Numerical results are then used to determine when and how many coded
packets should be inserted into the packet stream, in addition to determining
the trade-offs between reducing the in-order delay and the achievable rate. The
analytical results are finally compared with experimental results to provide
insight into how to minimize the delay of existing transport layer protocols
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