A Smart Checkpointing Scheme for Improving the Reliability of Clustering Routing Protocols

In wireless sensor networks, system architectures and applications are designed to consider both resource constraints and scalability, because such networks are composed of numerous sensor nodes with various sensors and actuators, small memories, low-power microprocessors, radio modules, and batteries. Clustering routing protocols based on data aggregation schemes aimed at minimizing packet numbers have been proposed to meet these requirements. In clustering routing protocols, the cluster head plays an important role. The cluster head collects data from its member nodes and aggregates the collected data. To improve reliability and reduce recovery latency, we propose a checkpointing scheme for the cluster head. In the proposed scheme, backup nodes monitor and checkpoint the current state of the cluster head periodically. We also derive the checkpointing interval that maximizes reliability while using the same amount of energy consumed by clustering routing protocols that operate without checkpointing. Experimental comparisons with existing non-checkpointing schemes show that our scheme reduces both energy consumption and recovery latency

Design, Implementation, and Performance Evaluation of a Detection-Based Adaptive Block Replacement Scheme

caching of disk blocks in the operating system. The proposed DEAR scheme automatically detects block reference patterns of applications and applies different replacement policies to different applications depending on the detected reference pattern. The detection is made by a periodic process and is based on the relationship between block attribute values, such as backward distance and frequency gathered in a period, and the forward distance observed in the next period. This paper also describes an implementation and performance measurement of the DEAR scheme in FreeBSD. The results from performance measurements of several real applications show that, compared with the LRU scheme, the proposed scheme reduces the number of disk I/Os by up to 51 percent (with an average of 23 percent) and the response time by up to 35 percent (with an average of 12 percent) in the case of single application executions. For multiple application executions, the results show that the proposed scheme reduces the number of disk I/Os by up to 20 percent (with an average of 12 percent) and the overall response time by up to 18 percent (with an average of 8 percent). Index TermsÐBuffer cache, FreeBSD, reference pattern, replacement policy, performance evaluation.

Impact of Mobility on Routing Energy Consumption in Mobile Sensor Networks

Mobility in mobile sensor networks causes frequent route breaks, and each routing scheme reacts differently during route breaks. It results in a performance degradation of the energy consumption to reestablish the route. Since routing schemes have various operational characteristics for rerouting, the impact of mobility on routing energy consumption shows significantly different results under varying network dynamics. Therefore, we should consider the mobility impact when analyzing the routing energy consumption in mobile sensor networks. However, most analysis of the routing energy consumption concentrates on the traffic condition and often neglects the mobility impact. We analyze the mobility impact on the routing energy consumption by deriving the expected energy consumption of reactive, proactive, and flooding scheme as a function of both the packet arrival rate and topology change rate. Routing energy consumption for mobile sensor networks is analytically shown to have a strong relationship with sensor mobility and traffic conditions. We then demonstrate the accuracy of our analysis through simulations. Our analysis can be used to decide a routing scheme that will operate most energy efficiently for a sensor application, taking into account the mobility as well as traffic condition

Enhancing the Reliability of Head Nodes in Underwater Sensor Networks

Underwater environments are quite different from terrestrial environments in terms of the communication media and operating conditions associated with those environments. In underwater sensor networks, the probability of node failure is high because sensor nodes are deployed in harsher environments than ground-based networks. The sensor nodes are surrounded by salt water and moved around by waves and currents. Many studies have focused on underwater communication environments in an effort to improve the data transmission throughput. In this paper, we present a checkpointing scheme for the head nodes to quickly recover from a head node failure. Experimental results show that the proposed scheme enhances the reliability of the networks and makes them more efficient in terms of energy consumption and the recovery latency compared to the previous scheme without checkpointing

On the Impossibility of Non-Blocking Consistent Causal Recovery

this paper, we consider the problem of the recovery in causallylogged distributed system and give a condition for consistent recovery. We then show that, based on the impossibility of the consensus, the consistent causal recovery cannot be solved in asynchronous systems

Efficient Cache Management Schemes for Reducing Duplication Caching between Buffer and Disk Caches

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