6,195 research outputs found
Time Synchronization in modular collaborative robots
A new generation of robot systems which are modular, flexible and safe for
human-robot interaction are needed. Existing cobots seem to meet only the later
and require a modular approach to improve their reconfigurability and
interoperability. We propose a new sub-class of cobots named M-cobots which
tackle these problems. In particular, we discuss the relevance of
synchronization for these systems, analyze it and demonstrate how with a
properly configured M-cobot, we are able to obtain a) distributed
sub-microsecond clock synchronization accuracy among modules, b) timestamping
accuracy of ROS 2.0 messages under 100 microseconds and c) millisecond-level
end-to-end communication latencies, even when disturbed with networking
overloads of up to 90% of the network capacity
Timing in Software-Defined and Centrally-Managed Networks
The work described in this paper explores the use of time and synchronized
clocks in centrally-managed and Software Defined Networks (SDNs). One of the
main goals of this work is to analyze use cases in which explicit use of time
is beneficial. Both theoretical and practical aspects of timed coordination and
synchronized clocks in centralized environments are analyzed. Some of the
products of this work are already incorporated in the OpenFlow specification,
and open source prototypes of the main components are publicly available.Comment: This paper summarizes "Using Time in Software Defined Networks", a
PhD dissertation that was submitted to the Technion in 2016. A preliminary
version of this paper appeared in the IEEE SDN Newsletter, "The TimedSDN
Project", November 201
Toward Adaptive Causal Consistency for Replicated Data Stores
Causal consistency for key-value stores has two main requirements (1) do not
make a version visible if some of its dependencies are invisible as it may
violate causal consistency in the future and (2) make a version visible as soon
as possible so that clients have the most recent information (to the extent
feasible). These two requirements conflict with each other. Existing key-value
stores that provide causal consistency (or detection of causal violation)
utilize a static approach in the trade-off between these requirements.
Depending upon the choice, it assists some applications and penalizes some
applications. We propose an alternative where the system provides a set of
tracking groups and checking groups. This allows the application to choose the
settings that are most suitable for that application. Furthermore, these groups
can be dynamically changed based on application requirements
Over-the-Air Time Synchronization for URLLC: Requirements, Challenges and Possible Enablers
Ultra-reliable and low-latency communications (URLLC) is an emerging feature
in 5G and beyond wireless systems, which is introduced to support stringent
latency and reliability requirements of mission-critical industrial
applications. In many potential applications, multiple sensors/actuators
collaborate and require isochronous operation with strict and bounded jitter,
e.g., \SI{1}{\micro\second}. To this end, network time synchronization becomes
crucial for real-time and isochronous communication between a controller and
the sensors/actuators. In this paper, we look at different applications in
factory automation and smart grids to reveal the requirements of device-level
time synchronization and the challenges in extending the high-granularity
timing information to the devices. Also, we identify the potential over-the-air
synchronization mechanisms in 5G radio interface, and discuss the needed
enhancements to meet the jitter constraints of time-sensitive URLLC
applications
Agent-time Epistemics and Coordination
A minor change to the standard epistemic logical language, replacing
with K_{\node{i,t}} where is a time instance, gives rise to a generalized
and more expressive form of knowledge and common knowledge operators. We
investigate the communication structures that are necessary for such
generalized epistemic states to arise, and the inter-agent coordination tasks
that require such knowledge. Previous work has established a relation between
linear event ordering and nested knowledge, and between simultaneous event
occurrences and common knowledge. In the new, extended, formalism, epistemic
necessity is decoupled from temporal necessity. Nested knowledge and event
ordering are shown to be related even when the nesting order does not match the
temporal order of occurrence. The generalized form of common knowledge does
{\em not} correspond to simultaneity. Rather, it corresponds to a notion of
tight coordination, of which simultaneity is an instance.Comment: 30 pages, 5 figure
Collaborative Localization and Tracking with Minimal Infrastructure
Localization and tracking are two very active areas of research for robotics,
automation, and the Internet-of-Things. Accurate tracking for a large number of
devices usually requires deployment of substantial infrastructure (infrared
tracking systems, cameras, wireless antennas, etc.), which is not ideal for
inaccessible or protected environments. This paper stems from the challenge
posed such environments: cover a large number of units spread over a large
number of small rooms, with minimal required localization infrastructure. The
idea is to accurately track the position of handheld devices or mobile robots,
without interfering with its architecture. Using Ultra-Wide Band (UWB) devices,
we leveraged our expertise in distributed and collaborative robotic systems to
develop an novel solution requiring a minimal number of fixed anchors. We
discuss a strategy to share the UWB network together with an Extended Kalman
filter derivation to collaboratively locate and track UWB-equipped devices, and
show results from our experimental campaign tracking visitors in the Chambord
castle in France.Comment: This paper is submitted to IROS201
A Survey of Routing Attacks and Security Measures in Mobile Ad-Hoc Networks
Mobile ad hoc networks (MANETs) are a set of mobile nodes which are
self-configuring and connected by wireless links automatically as per the
defined routing protocol. The absence of a central management agency or a fixed
infrastructure is a key feature of MANETs. These nodes communicate with each
other by interchange of packets, which for those nodes not in wireless range
goes hop by hop. Due to lack of a defined central authority, securitizing the
routing process becomes a challenging task thereby leaving MANETs vulnerable to
attacks, which results in deterioration in the performance characteristics as
well as raises a serious question mark about the reliability of such networks.
In this paper we have attempted to present an overview of the routing
protocols, the known routing attacks and the proposed countermeasures to these
attacks in various works.Comment: 7 pages journal of computing vol3 issue 1 january201
Energy Efficient MAC Protocols in Wireless Body Area Sensor Networks -A Survey
In this paper, we first presented an analytically discussion about energy
efficiency of Medium Access Control (MAC) protocols for Wireless Body Area
Sensor Networks (WBASNs). For this purpose, different energy efficient MAC
protocols with their respective energy optimization techniques; Low Power
Listening (LPL), Scheduled Contention and Time Division Multiple Access (TDMA),
are elaborated. We also analytically compared path loss models for In-body,
On-body and Off-body communications in WBASNs. These three path loss scenarios
are simulated in MATLAB and results shown that path loss is more in In-body
communication because of less energy level to take care of tissues and organs
located inside human body. Secondly, power model for WBASNs of Carrier Sense
Multiple Access with Collision Avoidance (CSMA/CA) and beacon mode is also
presented. MATLAB simulations results shown that power of CSMA/CA mode is less
as compared to beacon mode. Finally, we suggested that hybrid mode is more
useful to achieve optimization in power consumption, which consequently results
in high energy efficiency.Comment: arXiv admin note: substantial text overlap with arXiv:1207.256
Development of Quantum Interconnects (QuICs) for Next-Generation Information Technologies
Just as “classical” information technology rests on a foundation built of interconnected information-processing systems, quantum information technology (QIT) must do the same. A critical component of such systems is the “interconnect,” a device or process that allows transfer of information between disparate physical media, for example, semiconductor electronics, individual atoms, light pulses in optical fiber, or microwave fields. While interconnects have been well engineered for decades in the realm of classical information technology, quantum interconnects (QuICs) present special challenges, as they must allow the transfer of fragile quantum states between different physical parts or degrees of freedom of the system. The diversity of QIT platforms (superconducting, atomic, solid-state color center, optical, etc.) that will form a “quantum internet” poses additional challenges. As quantum systems scale to larger size, the quantum interconnect bottleneck is imminent, and is emerging as a grand challenge for QIT. For these reasons, it is the position of the community represented by participants of the NSF workshop on “Quantum Interconnects” that accelerating QuIC research is crucial for sustained development of a national quantum science and technology program. Given the diversity of QIT platforms, materials used, applications, and infrastructure required, a convergent research program including partnership between academia, industry, and national laboratories is required
Ultra-Low Latency (ULL) Networks: The IEEE TSN and IETF DetNet Standards and Related 5G ULL Research
Many network applications, e.g., industrial control, demand Ultra-Low Latency
(ULL). However, traditional packet networks can only reduce the end-to-end
latencies to the order of tens of milliseconds. The IEEE 802.1 Time Sensitive
Networking (TSN) standard and related research studies have sought to provide
link layer support for ULL networking, while the emerging IETF Deterministic
Networking (DetNet) standards seek to provide the complementary network layer
ULL support. This article provides an up-to-date comprehensive survey of the
IEEE TSN and IETF DetNet standards and the related research studies. The survey
of these standards and research studies is organized according to the main
categories of flow concept, flow synchronization, flow management, flow
control, and flow integrity. ULL networking mechanisms play a critical role in
the emerging fifth generation (5G) network access chain from wireless devices
via access, backhaul, and core networks. We survey the studies that
specifically target the support of ULL in 5G networks, with the main categories
of fronthaul, backhaul, and network management. Throughout, we identify the
pitfalls and limitations of the existing standards and research studies. This
survey can thus serve as a basis for the development of standards enhancements
and future ULL research studies that address the identified pitfalls and
limitations
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