Existing slotted channel access schemes in wireless networks assume that slot boundaries at all nodes are synchronized. In practice, relative clock drifts among nodes cause slot misalignment over time and can result i...
详细信息
ISBN:
(纸本)9781424404247
Existing slotted channel access schemes in wireless networks assume that slot boundaries at all nodes are synchronized. In practice, relative clock drifts among nodes cause slot misalignment over time and can result in catastrophic data loss in such systems. We propose a simple network-wide slot synchronization scheme (Slot-Sync and Slot-Resync) suitable for duty-cycling wireless sensor networks. The proposed scheme attains high accuracy by circumventing dominant sources of error inherent in traditional time synchronization protocols. At moderate duty-cycle frequencies, the proposed scheme also has the unique advantage of eliminating re-synchronization (re-sync) overhead completely, thereby achieving slot re-sync essentially for free. We provide an energy efficient slot guard time and resync interval design for the proposed scheme and analyze several spanning tree structures for slot-alignment message propagation. In addition, we derive upper bounds on the synchronization (sync) error for a family of trees. Through simulations, we compare the spanning trees we propose to those used for time sync in literature and show up to 80% reduction in sync error and up to 70% reduction in energy needed for slot-alignment message propagation by choosing appropriate tree structures.
Typical applications of wireless sensor networks require scalability because they are deployed in a large area. Conventional centralized systems for acoustic source localization experience practical difficulties since...
详细信息
In this paper, we study the fundamental limits of a wireless sensor network39;s lifetime under connectivity and k-coverage constraints. We consider a wireless sensor network with n sensors deployed independently and...
详细信息
The prevalence of emerging peer-to-peer (P2P) live broadcasting applications has practically demonstrated that they could scale to reliably support a large population of end users. However, these systems potentially s...
详细信息
ISBN:
(纸本)354038619X
The prevalence of emerging peer-to-peer (P2P) live broadcasting applications has practically demonstrated that they could scale to reliably support a large population of end users. However, these systems potentially suffer from two major threats: peers generally interact with unfamiliar partners without the benefit of trusted third party or verification authority, resulting in poor service if meeting with unreliable upstream nodes, while peers essentially tend to be selfish when it comes to the duty rather than the benefits and hence undermine the system performance. The trust and cooperation issues motivate us to investigate the design of trust-based incentive mechanism which establishes trustful relationship among peers and balances what they take from the system with what they contribute. The proposed TPOD mechanism leverages the statistical analysis to the practical service logs of client-server and P2P systems and effectively offers incentive through service differentiation. It goes beyond existing approaches in the following four desirable properties: (1)Trust-based;(2)Practical-oriented;(3)Objective metrics about past behaviors and (4)distributed nature upon gossip-based overlay. The experiment results over PlanetLab verify its effectiveness.
We consider applications of sensor networks wherein data packets generated by every node have to reach the base station. This results in a many-to-one communication paradigm referred to as convergecast. We are interes...
详细信息
An important class of applications for wireless sensor networks is to use the sensors to provide samples of a physical phenomenon at discrete locations. Through interpolation-based reconstruction, a continuous map of ...
详细信息
Advances in wireless networks, mobile devices and location tracking mechanisms are making location-aware applications more and more popular. While several prefetching schemes were proposed for mobile systems, very few...
详细信息
ISBN:
(纸本)0769525539
Advances in wireless networks, mobile devices and location tracking mechanisms are making location-aware applications more and more popular. While several prefetching schemes were proposed for mobile systems, very few ones exist for location-dependent applications. And at the best of our knowledge, there is no work describing implementation details of a prefetching scheme for location-dependent systems. In this paper, after a brief survey of information hoarding and prefetching mechanisms, we deduce some requirements for a successful prefetching scheme for location-aware applications, we show that the prefetching policy we previously proposed satisfies these requirements, and we describe a prototype implementing this policy. We describe the system architecture and detailed algorithms describing the tasks executed in the client and the server. We also discuss some additional steps that can be useful for saving energy consumption in the mobile device. An adequate data structure allows the server to have continuously an up to date image of the client's cache content.
MPLS fast reroute (MPLS-FRR) mechanisms deviate the traffic in case of network failures at the router closest to the outage location to achieve an extremely fast reaction time. We review the one-to-one backup and the ...
详细信息
ISBN:
(纸本)9781424404247
MPLS fast reroute (MPLS-FRR) mechanisms deviate the traffic in case of network failures at the router closest to the outage location to achieve an extremely fast reaction time. We review the one-to-one backup and the facility backup that are options for MPLS-FRR to deviate the traffic via a detour or a bypass around the failed elements, respectively. Basically, the backup paths can take the shortest path that avoids the outage location from the point of local repair to the tail-end router or to the merge point with the primary path. We suggest two simple modifications that lead to a new path layout which can be implemented by one-to-one and by facility backup. We evaluate the backup capacity requirements, the length of the backup paths, and the number of backup paths per primary path in a parametric study regarding the network characteristics. Our proposals save a considerable amount of backup capacity compared to the standard mechanisms. They are suitable for application in practice since they are simple and conform to the standards.
We consider the problem of data propagation in wireless sensor networks and revisit the family of mixed strategy routing schemes. We show that maximizing the lifespan, balancing the energy among individual sensors and...
详细信息
Without congestion control techniques specifically designed for sensor network applications, the system may not function properly due to data transmission failure. Moreover, most many-to-one communication schemes adop...
详细信息
ISBN:
(纸本)3540380914
Without congestion control techniques specifically designed for sensor network applications, the system may not function properly due to data transmission failure. Moreover, most many-to-one communication schemes adopted by sensor network applications cause a practical congestion problem called the funneling effect. With this problem, the hottest area is confined to the connection between the sink and its neighbors. In order to solve the bottleneck problem, we propose a congestion-control technique which uses adaptive time-slot scheduling and a service-differentiated technique. The simulation results show that the proposed method outperforms the conventional technique.
暂无评论