Preemptive Routing Research Articles

Enabling Real-Time Video Services over Ad-Hoc Networks Opens the Gates for E-learning in Areas Lacking Infrastructure

In this paper we suggest a promising solution to come over the problems of delivering e-learning to areas with lack or deficiencies in infrastructure for Internet and mobile communication. We present a simple, reasonably priced and efficient communication platform for providing e-learning. This platform is based on wireless ad-hoc networks. We also present a preemptive routing protocol suitable for real-time video communication over wireless ad-hoc networks. Our results show that this routing protocol can significantly improve the quality of the received video. This makes our suggested system not only good to overcome the infrastructure barrier but even capable of delivering a high quality e-learning material.

Prediction-Based Routing for Vehicular Ad Hoc Networks

Development in short-range wireless LAN (WLAN) and long-range wireless WAN (WWAN) technologies have motivated recent efforts to integrate the two. This creates new application scenarios that were not possible before. Vehicles with only WLAN radios can use other vehicles that have both WLAN and WWAN radios as mobile gateways and connect to the Internet while on the road. The most difficult challenge in the scenario is to deal with frequent route breakages due to dynamic mobility of vehicles on the road. Existing routing protocols that are widely used for mobile ad hoc networks are reactive in nature and wait until existing routes break before constructing new routes. The frequent route failures result in a significant amount of time needed for repairing existing routes or reconstructing new routes. In spite of the dynamic mobility, the motion of vehicles on highways is quite predictable compared to other mobility patterns for wireless ad hoc networks, with location and velocity information readily available. This can be exploited to predict how long a route will last between a vehicle requiring Internet connectivity and the gateway that provides a route to the Internet. Successful prediction of route lifetimes can significantly reduce the number of route failures. In this paper, we introduce a prediction-based routing (PBR) protocol that is specifically tailored to the mobile gateway scenario and takes advantage of the predictable mobility pattern of vehicles on highways. The protocol uses predicted route lifetimes to preemptively create new routes before existing ones fail. We study the performance of this protocol through simulation and demonstrate significant reductions in route failures compared to protocols that do not use preemptive routing. Moreover, we find that the overhead of preemptive routing is kept in check due to the ability of PBR to predict route lifetimes.

Semi–preemptive routing on a line

Abstract The problem of routing a robot (or vehicle) between n stations in the plane in order to transport objects is well studied, even if the stations are specially arranged, e.g. on a linear track or circle. The robot may use either all or none of the stations for reloading. We will generalize these concepts of preemptiveness/non–preemptiveness and emancipate the robot by letting it choose k ⩽ n reload–stations.

Performance analysis of optical packet switches with a hybrid buffering architecture [Invited

Feature Issue on Next-Generation WDM Network Design and Routing (WDMN). Optical fiber delay line (FDL) is currently the only technology available for implementing optical buffering. Feed-forward and feedback are two types of FDL structures in optical buffering, both of which have advantages and disadvantages. We present what we believe to be a novel architecture for WDM optical packet switches with an effective hybrid FDL buffering configuration that combines the merits of both feed-forward and feedback schemes. The core of the switch architecture is a number of arrayed waveguide gratings (AWG) and tunable wavelength converters (TWC). It requires smaller optical device sizes and fewer wavelengths and experiences less noise than feedback architecture. At the same time, it supports preemptive priority routing such as feedback architecture. Empirical results show that the proposed new switch architecture significantly reduces packet-loss probability.

Preemptive routing in ad hoc networks

Routing in ad hoc networks is a challenging problem because nodes are mobile and links are continuously being created and broken. Existing on-demand ad hoc routing algorithms initiate route discovery only after a path breaks, incurring a significant cost in detecting the disconnection and establishing a new route. In this work, we investigate adding proactive route selection and maintenance to on-demand ad hoc routing algorithms. More specifically, when a path is likely to be broken, a warning is sent to the source indicating the likelihood of a disconnection. The source can then initiate path discovery early, potentially avoiding the disconnection altogether. A path is considered likely to break when the received packet power becomes close to the minimum detectable power (other approaches are possible). Care must be taken to avoid initiating false route warnings due to fluctuations in received power caused by fading, multipath effects and similar random transient phenomena. Experiments demonstrate that adding proactive route selection and maintenance to DSR and AODV (on-demand ad hoc routing protocols) significantly reduces the number of broken paths, with a small increase in protocol overhead. Packet latency and jitter go down in most cases. Because preemptive routing reduces the number of broken paths, it also has a secondary effect on TCP performance—unnecessary congestion handling measures are avoided. This is observed for TCP traffic under different traffic patterns (telnet, ftp and http). Additionally, we outline some problems in TCP performance in ad hoc environments.