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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,...
We define an ad hoc transportation system as one that has no infrastructure such as roads (and lanes), traffic lights etc. We assume that in such a system the vehicle are autonomic and can guide and direct themselves without a human driver. In this paper we investigate how a safe distance can be maintained between vehicles. A vehicle which has been compromised by an adversary can cause serious chaos...
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...
Vehicular ad hoc networks (VANETs), similar to other distributed systems, often require a scalable time synchronization service enabling data consistency and coordination. In this paper, we propose a new time synchronization protocol for VANETs, which provides excellent scalability, accuracy and robustness for high mobility traffic scenarios. The new protocol, Converging Time Synchronization (CTS),...
Location-based routing intends to send packets toward geographic direction of destination. For this, source nodes needs to known about destination position via a location service. Whereas the main concept of ad hoc networking is being independent from an infrastructure, applying a distribution algorithm has been a key design principle for a location service. Destruction of single nodes shouldn't lead...
This paper proposes a RSU assisted multi-channel coordination MAC (RAMC) protocol that fully utilizes all DSRC channels to provide simultaneous safety and non-safety communications. Within the radio range of a roadside unit (RSU), vehicles are free to tune to any service channels. The RSU monitors all the safety messages being transmitted in both the control and service channels. Periodically, the...
This paper provides an overview of IEEE 1609.4, a work in progress standard for multi-channel operations over the 5.9 GHz Dedicated Short Range Communications (DSRC) spectrum. In the U.S., the DSRC spectrum is organized into several channels. IEEE 1609.4 defines a time-division scheme for DSRC radios to alternately switch within these channels to support different applications concurrently. We describe...
Wireless sensor network characteristics contain limited power to store, ability to withstand harsh environmental conditions, ability to cope with node failures, mobility of nodes, dynamic network topology, heterogeneity of nodes, communication failures and large scale of deployment. The traditional cryptographic protocol models are not suitable in low power sensor nodes due to inherent resource and...
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...
Extending system lifetime by effectively managing power on participating nodes is critical in wireless ad hoc networks. One critical issue for almost all kinds of wireless devices supported by battery powers is power saving (PS). The PS protocols for MANET can be categorized into synchronous and asynchronous ones. The synchronous PS protocol can not be applied to a multi-hop MANET, because it will...
The Digital Mobile Radio (DMR) is a European digital trunked system standard proposed in 2006. Digital trunked radio system is a special mobile communication system that helps to enhance the work efficiency and security. The DMR over-the-air protocol from ETSI specifies the 4-level Continuous Phase Frequency Shift Keying (CPFSK) as its standard modulation scheme. In this paper, we propose a digital...
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...
Security is amongst one of the major issues in broadband wireless access (BWA) networks. After the launch of the IEEE 802.16 standard (WiMAX), a number of security issues were reported in several articles. Ever since the beginning, work has been in progress for the neutralization of these identified threats. In this paper, the analysis of the authentication protocols implemented in WiMAX has been...
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...
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