Jiman Hong

Adaptive page-level incremental checkpointing based on expected recovery time

Incremental checkpointing, which is intended to minimize checkpointing overhead, saves only the modified pages of a process. This means that in incremental checkpointing, the time consumed for checkpointing varies according to the amount of modified pages. Thus, an efficient interval of checkpointing have to be determined on run-time of a process. In this paper, we present an efficient and adaptive page-level incremental checkpointing facility that is based on the interval determination mechanism for minimizing the expected execution time. Our simulation results show that the expected execution time was significantly reduced compared with existing periodic page-level incremental checkpointing.

Space-efficient page-level incremental checkpointing

Incremental checkpointing, which is intended to minimize checkpointing overhead, saves only the modified pages of a process. However, the cumulative size of incremental checkpoints increases at a steady rate over time because many updated values may be saved for the same page. In this paper, we present a comprehensive overview of Pickpt, which is a page-level incremental checkpointing facility. Pickpt provides space-efficient techniques for minimizing the use of disk space. For our experiments, the results show that the use of disk space of Pickpt was significantly reduced compared with existing incremental checkpointing.

Adaptive mobile checkpointing facility for wireless sensor networks

In wireless sensor networks, many kinds of failures may arise on sensor nodes because the nodes can be deployed and used even in harsh environments. Therefore, fault-tolerance mechanisms are needed for the wireless sensor networks have to maintain stability and normal operation of the networks. In this paper, we propose an adaptive mobile checkpointing mechanism for wireless sensor networks that gives fault-tolerance for the networks. It is a yet another checkpointing mechanism based on the diskless checkpointing which does not use stable storage but uses the redundant memory space of neighboring nodes. Our experimental results show that the lifetime and stability of sensor networks was dramatically increased compared with the case when the proposed mechanism was used or not.

EAR-RT: energy aware routing with real-time guarantee for wireless sensor networks

Most energy aware routing algorithms focus on the increasing the lifetime and long-term connectivity of the wireless sensor networks. But energy efficiency sacrifices the communication delay between source and sink node. Therefore, many researchers have mentioned of energy and delay trade-offs. But the delay was not the main concern. In this paper we propose EAR-RT, an real-time guaranteed routing protocol for wireless sensor networks without harming energy awareness. Simulation results show that our real-time routing algorithm provides real-time guaranteed delivery while network is stable.

An efficient dynamic memory allocator for sensor operating systems

Dynamic memory allocation mechanism is important aspect of operating system, because an efficient dynamic memory allocator improves the performance of operating systems. In wireless sensor networks, sensor nodes have miniature computing device, small memory space and very limited battery power. Therefore, sensor operating systems should be able to operate efficiently in terms of energy consumption and resource management. And the role of dynamic memory allocator in sensor operating system is more important than one of general operating system. In this pager, we propose new dynamic memory allocation scheme that solves problems of existing dynamic memory allocators. We implement our scheme on Nano-Qplus which is a sensor operating system base on multi-threading. Our experimental results show our scheme performs efficiently in both time and space compared with existing memory allocation mechanism.

Energy aware routing based on adaptive clustering mechanism for wireless sensor networks

The main goal of research concerning energy aware routing algorithm for wireless sensor network is to increase the lifetime and long-term connectivity of the wireless sensor networks. However, most of energy aware routing algorithms do not take into account the clustering mechanism efficiently. In this paper, we present an efficient energy aware routing algorithm for the wireless sensor networks. In our algorithm, the data aggregation technique and adaptive clustering mechanism are considered for reducing and compacting the cumulative size of packets on the wireless sensor networks. Simulation results show that the energy usage of EAR-ACM is significantly reduced compared with the previous clustering based routing algorithm for the sensor networks.

On the choice of checkpoint interval using memory usage profile and adaptive time series analysis

This paper presents a new checkpoint scheme that utilizes the memory usage profile and time series analysis for low-overhead checkpoint. The proposed checkpoint scheme checks current and future checkpoint overhead based on the on the changes of the memory size and the expected checkpoint overhead using memory profile and adaptive time series analysis when it decides whether or not to take a checkpoint. Unlike the previous works that do not utilize the memory usage profile, it is possible to reduce the total overhead of the execution time. We also present experimental results which show that the checkpoint overhead of the proposed scheme is reduced compared with the previously developed checkpoint scheme.

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.

Dynamic Memory Allocator for Sensor Operating System Design and Analysis

Dynamic memory allocation is an important mechanism used in operating systems. An efficient dynamic memory allocator can improve the performance of operating systems. In wireless sensor networks, sensor nodes have miniature computing device, small memory space and very limited battery power. Therefore, it is important that sensor operating systems operate efficiently in terms of energy consumption and resource management. And the role of dynamic memory allocator in sensor operating system is more important than one of general operating system. In this paper, we propose a new dynamic memory allocation scheme that resolves the existing problems in dynamic memory allocators. We implemented our scheme on Nano-Qplus which is a sensor operating system based on multi-threading. Our experimental results and static analysis result show our scheme performs efficiently in terms of the execution time and the memory space compared with existing memory allocation mechanisms.

Performance analysis of task schedulers in operating systems for wireless sensor networks

In wireless sensor networks, power is a critical resource in battery powered sensor nodes. In this respect, as it is important to efficiently utilize the limited battery power, it would be desirable to make such nodes as energy efficient as possible. Many researchers who develop operating systems of wireless sensor networks have been trying to find a way to enhance energy efficiency of sensor nodes. In this paper, we present an overview of sensor node operating systems and some of its functionalities, and then present a performance analysis of task schedulers and task-related kernel routines of existing sensor node operating systems. The results of performance analysis show some advantages and disadvantages of the existing operating systems, and based on these information, we present some possible improvements for increasing the efficiency of sensor node operating systems.