437 research outputs found
Multimedia Content Distribution in Hybrid Wireless Networks using Weighted Clustering
Fixed infrastructured networks naturally support centralized approaches for
group management and information provisioning. Contrary to infrastructured
networks, in multi-hop ad-hoc networks each node acts as a router as well as
sender and receiver. Some applications, however, requires hierarchical
arrangements that-for practical reasons-has to be done locally and
self-organized. An additional challenge is to deal with mobility that causes
permanent network partitioning and re-organizations. Technically, these
problems can be tackled by providing additional uplinks to a backbone network,
which can be used to access resources in the Internet as well as to inter-link
multiple ad-hoc network partitions, creating a hybrid wireless network. In this
paper, we present a prototypically implemented hybrid wireless network system
optimized for multimedia content distribution. To efficiently manage the ad-hoc
communicating devices a weighted clustering algorithm is introduced. The
proposed localized algorithm deals with mobility, but does not require
geographical information or distances.Comment: 2nd ACM Workshop on Wireless Multimedia Networking and Performance
Modeling 2006 (ISBN 1-59593-485
Traffic agents for improving QoS in mixed infrastructure and ad hoc modes wireless LAN
As an important complement to infrastructured wireless networks, mobile ad hoc networks (MANET) are more flexible in providing wireless access services, but more difficult in meeting different quality of service (QoS) requirements for mobile customers. Both infrastructure and ad hoc network structures are supported in wireless local area networks (WLAN), which can offer high data-rate wireless multimedia services to the mobile stations (MSs) in a limited geographical area. For those out-of-coverage MSs, how to effectively connect them to the access point (AP) and provide QoS support is a challenging issue. By mixing the infrastructure and the ad hoc modes in WLAN, we propose in this paper a new coverage improvement scheme that can identify suitable idle MSs in good service zones as traffic agents (TAs) to relay traffic from those out-of-coverage MSs to the AP. The service coverage area of WLAN is then expanded. The QoS requirements (e.g., bandwidth) of those MSs are considered in the selection process of corresponding TAs. Mathematical analysis, verified by computer simulations, shows that the proposed TA scheme can effectively reduce blocking probability when traffic load is light
Distributed scheduling with end-to-end compensation in multihop ad hoc networks
In this paper, we investigate the problem of providing QoS to end-to-end flows in multihop ad hoc networks with channel errors through packet scheduling. Each flow is associated with some QoS requirement, which is requested and granted in the form of a desired service rate. The achieved rate is estimated at the destination and fed back to the source periodically. Both the desired rate and achieved rate of a multihop flow are piggybacked on the packets of the flow and propagated from the source node to all its downstream relaying nodes. With such information, a compensation-capable scheduling algorithm originally designed for infrastructured wireless networks can be adapted to each ad hoc node for compensating a lagging flow, i.e., a flow with the achieved rate smaller than the desired rate. We propose the feedback and propagation mechanism as an end-to-end compensation framework, which is the key contribution of this work. We use BGFS-EBA, a scheduling algorithm for infrastructured wireless networks, as an example to demonstrate how such an algorithm is adapted to ad hoc networks within the proposed framework. Our simulation results show that the proposed mechanism maintains outcome fairness and compensate flows that suffer sporadic bursty channel errors effectively. © 2008 IEEE.published_or_final_versionThe 19th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, Cannes, France, 15-18 September 2008. In Proceedings of 19th IEEE PIMRC, 2008, p. 1-
Messiah: An ITS drive safety application
This article describes a novel safety application based on the open source navigation software OsmAnd,
which runs on the Android platform. The application offers vehicles with "smart navigation", and maintains a network
of the vehicles that use our application. The process of network creation and maintenance is important as
our application enables vehicles to communicate with one another to exchange useful information. The main
function of the application is to inform vehicles of relevant vehicles approaching, termed as "administrative
vehicles" in this article, and include ambulances, police cars and fire brigades. Based on the received
information, our application notifies the driver, who can now take navigation decisions based on it. While developing
the application, problems were found when attempting to create an Ad-hoc network. A solution to the problem of managing the Ad-hoc network has been proposed and is under development
Experimentation with MANETs of Smartphones
Mobile AdHoc NETworks (MANETs) have been identified as a key emerging
technology for scenarios in which IEEE 802.11 or cellular communications are
either infeasible, inefficient, or cost-ineffective. Smartphones are the most
adequate network nodes in many of these scenarios, but it is not
straightforward to build a network with them. We extensively survey existing
possibilities to build applications on top of ad-hoc smartphone networks for
experimentation purposes, and introduce a taxonomy to classify them. We present
AdHocDroid, an Android package that creates an IP-level MANET of (rooted)
Android smartphones, and make it publicly available to the community.
AdHocDroid supports standard TCP/IP applications, providing real smartphone
IEEE 802.11 MANET and the capability to easily change the routing protocol. We
tested our framework on several smartphones and a laptop. We validate the MANET
running off-the-shelf applications, and reporting on experimental performance
evaluation, including network metrics and battery discharge rate.Comment: 6 pages, 7 figures, 1 tabl
Performance evaluation of wireless IEEE 802.11(b) used for ad-hoc networks in an e-learning classroom network
Evaluation of wireless networks for performance evaluation is a popular research area and a wealth of literature exists in this area. Wireless networks in infrastructure mode as well as Ad-hoc networks such as MANETs are considered extensively. Simulation results are provided for E-learning scenarios for cases where wireless networks in infrastructure mode are employed, however the possibilities of using ad- hoc networks and performance evaluation of e-learning scenarios with ad hoc networks are not considered. This paper presents an evaluation of the performances for wireless Ad-hoc networks employed in typical e-learning environment by using the OPNET modeller. Numerical simulation results, discussions and comparisons are provided. The results can be of great help for optimisation studies in typical e-learning environments. The performance issues are considered together with scalability concerns
Distributed opportunistic scheduling in multihop wireless ad hoc networks
In this paper, we introduce a framework for distributed opportunistic scheduling in multihop wireless ad hoc networks. With the proposed framework, one can take a scheduling algorithm originally designed for infrastructure-based wireless networks and adapt it to multihop ad hoc networks. The framework includes a wireless link state estimation mechanism, a medium access control (MAC) protocols and a MAC load control mechanism. The proposed link state estimation mechanism accounts for the latest results of packet transmissions on each wireless link. To improve robustness and provide service isolation during channel errors, the MAC protocol should not make any packet retransmissions but only report the transmission result to the scheduler. We modify IEEE 802.11 to fulfill these requirements. The MAC load control mechanism improves the system robustness. With link state information and the modified IEEE 802.11 MAC, we use BGFS-EBA, an opportunistic scheduling algorithm for infrastructured wireless networks, as an example to demonstrate how such an algorithm is converted into its distributed version within the proposed framework. The simulation results show that our proposed method can provide robust outcome fairness in the presence of channel errors. ©2008 IEEE.published_or_final_versio
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