Wait Routing Research Articles

Spray and Wait Routing With Agents in Intermittently Connected MANETs

Spray and Wait Routing With Agents in Intermittently Connected MANETs

Spray and Wait routing based on ACK-mechanism in disruption tolerant networks

Disruption Tolerant Network(DTN) attempts to transfer messages via intermittently connected nodes.The difficulty lies in that the routing connectivity is opportunistic,and the network topology information is lacking between nodes.Spray and Wait is an efficient routing scheme in such environment,it sprays a number of copies into the network,and then waits till one of these nodes meets the destination.Compared with epidemic routing,Spray and Wait consumes less network resources,but still suffers from severe contention under high network load.Therefore,based on the analysis of Spray and Wait routing,an ACK-mechanism was used to remove the redundant messages which lead to less network resource consumption.Meanwhile,token forwarding was adopted in order to improve the bandwidth utilization.The improved routing scheme was simulated on ONE platform and the simulation results show that it has higher average delivery rate and consumes fewer network resources though it has slight higher average delivery delay.The scheme works well in intermittently connected mobile networks without any priori connectivity knowledge.

Vibrant Energy Aware Spray and Wait Routing in Delay Tolerant Network

Delay tolerant networks (DTN) are wireless networks where disconnections arise often due to the mobility of nodes, failures of energy, the low density of nodes, or when the network extends over long distances. In these situations, traditional routing protocols that have been developed for mobile ad hoc networks prove to be unsuccessful to the scope of transmitting messages between nodes. The Spray and Wait routing may achieve low routing and energy efficiency due to the blindness in the spray phase. To deal with this situation, we propose an opportunistic routing with enclosed message copies, called the Vibrant Energy aware Spray and Wait (VESW), which utilizes the information about vibrancy of node and remaining energy to allocate the number of copies between the corresponding pair nodes in the spray phase.

An Improved Spray and Wait with Probability Choice Routing for Opportunistic Networks

Opportunistic networks are sparse multi-hop ad hoc networks in which nodes exploit any pair-wise contact opportunities to share and forward messages. The main challenge for this environment is that conventional routing schemes do not work properly. Among the existing Opportunistic Networks routing algorithms, the epidemic routing and probabilistic routing could provide higher delivery probability and shorter delays, but is with a large overhead, while the spay and wait routing could reduce the overhead, but is with low delivery probability and high delay. This paper proposes the Spray and Wait with Probability Choice (SWPC) routing, where continuous encounter time is used to describe the encounter opportunity; a delivery probability function is set up to direct the different number of copies to the destination during the spray phase; and a forwarding scheme is implemented in the wait phase. Simulation results show that proposed SWPC shows prominent superiority in the delivery rate, the average delay and the communication overhead, and adapted for the frequently disconnected opportunistic network.

Performance assessment of IP over vehicular delay-tolerant networks through the VDTN@Lab testbed

Abstract Vehicular delay-tolerant network (VDTN) is a network architecture based on the delay-tolerant network paradigm, which was designed to provide low-cost asynchronous vehicular communications in environments with disruptions, intermittency, variable delays, and network partition. This article proposes a laboratory testbed for VDTNs, called VDTN@Lab. It aims to support research studies related with the design, emulation, performance evaluation, and diagnose of new VDTN protocols, services, and applications. It intends to demonstrate the applicability of VDTNs over multiple application environments. VDTN@Lab features an emulation capability, allowing live experiments with prototyped hardware and software embedded into robotic cards, desktop, and netbooks computers. The proposed prototype is demonstrated and evaluated with Epidemic, and Spray, and Wait routing protocols, using different combinations of scheduling and dropping policies, in scenarios with different vehicular mobility models (bus movement and random movement across roads).

Spray and forward: Efficient routing based on the Markov location prediction model for DTNs

Typical delay tolerant networks (DTNs) often suffer from long and variable delays, frequent connectivity disruptions, and high bit error rates. In DTNs, the design of an efficient routing algorithm is one of the key issues. The existing methods improve the accessibility probability of the data transmission by transmitting many copies of the packet to the network, but they may cause a high network overhead. To address the tradeoff between a successful delivery ratio and the network overhead, we propose a DTN routing algorithm based on the Markov location prediction model, called the spray and forward routing algorithm (SFR). Based on historical information of the nodes, the algorithm uses the second-order Markov forecasting mechanism to predict the location of the destination node, and then forwards the data by greedy routing, which reduces the copies of packets by spraying the packets in a particular direction. In contrast to a fixed mode where a successful-delivery ratio and routing overhead are contradictory, a hybrid strategy with multi-copy forwarding is able to reduce the copies of the packets efficiently and at the same time maintain an acceptable successful-delivery ratio. The simulation results show that the proposed SFR is efficient enough to provide better network performance than the spray and wait routing algorithm, in scenarios with sparse node density and fast mobility of the nodes.

Simulation Modeling for the Health Care Manager

This article addresses the use of simulation software to solve administrative problems faced by health care managers. Spreadsheet add-ins, process simulation software, and discrete event simulation software are available at a range of costs and complexity. All use the Monte Carlo method to realistically integrate probability distributions into models of the health care environment. Problems typically addressed by health care simulation modeling are facility planning, resource allocation, staffing, patient flow and wait time, routing and transportation, supply chain management, and process improvement.