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OWD is becoming increasingly important nowadays, as SLA agreements use it as a parameter to ensure QoS levels. However, its measurement is still a much debated topic due to the difficulty in the clock synchronization process. The paper approaches a new methodology to measure OWD, using NTP protocol with virtual clocks and bigger packets. This approach works over a measurement tool developed by the...
Clock synchronization is of critical importance for several applications in wireless and mobile sensor networks; for example to determine the order and time of events. Although several protocols to achieve clock synchronization have been developed, they may not be secure. For instance, a link controlled by an attacker could delay packets it forwards in ways which would cause the nodes sharing that...
Service discovery is an essential step in deploying many wireless network applications. The design of service discovery protocols is particularly challenging for mobile wireless networks because of their dynamic and unstructured nature. Most of the previously proposed protocols are based on the assumption that there exists an end-to-end connection from the query source node to the destination node,...
Global clock synchronization is important to mobile wireless multihop networks that require precise timing information for data collection and energy conservation in MAC layer protocols. In this paper, we propose a global clock synchronization protocol for Delay Tolerant Network (DTN). The protocol achieves global clock synchronization under asynchronous, long delayed, and intermittent network dynamics...
In this paper we address the Quality of Service (QoS) issues for applications such as voice and video that generate bursty traffic in mobile ad hoc networks while asynchronous power saving protocols are applied to wireless hosts. To provide QoS, we propose our new quorum-based power saving protocol called "consecutive quorum-based power saving (CQPS)". Within this torus-based protocol each...
Several promising applications for Vehicular Ad-hoc Networks (VANETs) exist. For most of these applications, the communication among vehicles is envisioned to be based on the broadcasting of messages. This is due to the inherent highly mobile environment and importance of these messages to vehicles nearby. To deal with broadcast communication, dissemination protocols must be defined in such a way...
Communication networks for industrial automation are usually heterogeneous, i.e. a combination of different wired and wireless technologies. A possible setup could be a Real-time Ethernet (RTE) extended by a wireless local area network (WLAN) for all mobile system components. However, the required clock synchronization with IEEE 1588v2 for such a system can only be accomplished for the wired RTE part...
Wireless sensor networks operate in constrained environments. In addition to the limitations in terms of energy, memory and computation, the use of mobile sensors has recently been contemplated. However, only a few medium access control protocols consider the dynamic of such scenarios. In this paper, we present potential problems that could arise with nowadays protocols operating in mobile environments...
Broadcasting of digital video signals uses large spectral area. In order to reduce the cost, broadcasters are optimizing their radio network. They build single frequency network (SFN). To maintain efficient quality of service (QoS) to the end user, accurate time synchronization and frequency syntonization is needed between transmitter sites. This function is now fulfilled with local GPS slaved clocks...
The Timeslot Boundary Synchronization Problem occurs when timeslot boundaries become aligned leading to an increase in the probability of message collisions. This alignment, which can occur in Vehicular Ad Hoc Networks using the 802.11p protocols, adversely affects the performance of multi-hop message broadcasts. This paper describes the causes of this phenomenon and describes link and network layer...
Based on the technology of Mobile Ad-hoc Network (MANET), we design and implement an Audio Conferencing Testbed (ACT) that is used for a group of people to set up virtual audio conferencing room to complete certain mission in places where network infrastructure is unavailable. ACT is built on popular Windows operating system with off-the-shelf IEEE802.lt (a.k.a. Wi-Fi) adapters as the enabling technology...
Although many medium access control (MAC) protocols have been specifically designed for WSNs where energy awareness is an essential consideration, only a few of them have considered the presence of mobile nodes or dynamic network topology in their protocols. However, they have usually considered occasional mobility, in which a few number of nodes may start moving at very low speeds and then remained...
Mobile ad-hoc networks (MANET) are often characterized with rapidly changing topologies, presenting a constant challenge for time synchronization. This challenge holds especially true in tactical edge ground military networks, where topological instabilities are enhanced by hostile transmission environments. In the absence of GPS, time synchronization within the context of a tactical environment requires...
Sensor networks are now enabling the monitoring of various environmental phenomena with more accuracy than the previous labour intensive and less technological solutions. This paper is concerned with the application of opportunistic networking techniques to wildlife monitoring, where the sensors are attached to animals moving in their habitat. We present seal-2-seal, a novel protocol for logging of...
Interest on using mobile autonomous agents has been growing, recently, due to their capacity to cooperate for diverse purposes, from rescue to demining and security. However, such cooperation requires the exchange of state data that is time sensitive while achieving timeliness with RF communication is intrinsically difficult due to the openess of the medium. This paper describes a communication layer...
Network time synchronization (NTS) is essential for any distributed systems, including disruption tolerant networks (DTNs). The feature of frequent contact disruptions and discontinuous network connections in DTNs raises a new challenge in providing the NTS service: synchronization operations may be interrupted for a long period of time when links between the time synchronization peers are opportunistic...
This contribution addresses the case when live packet-switched video is used to enrich circuit-switched speech calls in mobile telephony. Circuit-switched and packet-switched transmissions generally operate on completely different transmission paths resulting in different QoS in terms of delay and loss rates. In this case, video and audio data recorded at the same time are not multiplexed together...
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