• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.7 s.349
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• pp.1-13
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• 2006

In this paper, we introduce a novel key management scheme that is based on the key pre-distribution but provides the key re-distribution method, in order to manage keys for message encryption and authentication of lower-layer sensor nodes on hierarchical mobile sensor networks. The characteristics of our key management are as follows: First, the role of key management is distributed to aggregator nodes as well as a sink node, to overcome the weakness of centralized management. Second, a sink node generates keys using regression model, thus it stores only the information for calculating the keys using the key information received from nodes, but does not store the relationship between a node and a key, and the keys themselves. As the disadvantage of existing key pre-distributions, they do not support the key re-distribution after the deployment of nodes, and it is hard to extend the key information in the case that sensor nodes in the network enlarge. Thirdly, our mechanism provides the resilience to node capture(${\lambda}$-security), also provided by the existing key pre-distributions, and fourth offers the key freshness through key re-distribution, key distribution to mobile nodes, and scalability to make up for the weak points in the existing key pre-distributions. Fifth, our mechanism does not fix the relationship between a node and a key, thus supports the anonymity and untraceability of mobile nodes. Lastly, we compare ours with existing mechanisms, and verify our performance through the overhead analysis of communication, computation, and memory.

• Journal of Internet Computing and Services
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• v.10 no.1
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• pp.43-50
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• 2009

Flooding and SPIN, which are well-known WSN(Wireless Sensor Network) proactive protocols, spontaneously disseminate the sensed data without a request from an arbitrary sink node. However, these methods disseminate the data even to some nodes that do not need it, which is energy inefficient. In this paper, we introduce a semi-proactive protocol to disseminate only to pertinent nodes instead of all nodes in order to overcome this weakness. Thus some nodes, such as arbitrary sink nodes that need the sensed data, could easily obtain the data within some hops. The simulation result shows that the proposed protocol has higher average node energy efficiency than that of well-known earlier work, SPIN. If a proactive protocol, such as SPIN, is changed to semi-proactive and has only a 1-hop burden, then the energy efficiency enhancement is up to about 83% compared with SPIN.

• Journal of Korea Multimedia Society
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• v.17 no.8
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• pp.977-987
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• 2014

Many of the recent performance evaluation of clustering schemes in wireless sensor networks considered one sink node operation and fixed sink node location without mentioning about any network application requirements. However, application environments have variable requirements about their networks. In addition, network performance is sufficiently influenced by different sink node location scenarios in multi-hop based network. We also know that sink location can influence to the sensor network performance evaluation because of changed multipath of sensor nodes and changed overload spots in multipath based wireless sensor network environment. Thus, the performance evaluation results are hard to trust because sensor network is easily changed their network connection through their routing algorithms. Therefore, we suggest that these schemes need to evaluate with different sink node location scenarios to show fair evaluation result. Under the results of that, network performance evaluation results are acknowledged by researchers. In this paper, we measured several clustering scheme's performance variations in accordance with various types of sink node location scenarios. As a result, in the case of the clustering scheme that did not consider various types of sink location scenarios, fair evaluation cannot be expected.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.4
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• pp.77-82
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• 2020

Wireless sensor networks (WSNs) suffer from not only a short lifetime due to limited energy but also an energy imbalance between nodes close to the sink and others. In order to fundamentally solve the short lifetime, recent studies utilize the environmental energy such as solar power. Additionally, WSNs using mobile sinks are being studied to address the energy imbalance problem. This paper proposes an improved CTP (Collection Tree Protocol) scheme which uses these two approaches simultaneously. Basically, it is based on a CTP scheme which is a very popular data collection strategy designed for the typical battery-based WSNs with a fixed sink. Therefore, we tailored it for solar-powered WSNs with a mobile sink. Performance verification confirms that our scheme reduces the number of blackout nodes significantly compared to the typical CTP, thus increases the amount of data collected by the sink.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.585-593
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• 2010

Geographic routing has been considered as an efficient, simple, and scalable routing protocol for wireless sensor networks since it exploits pure local location information instead of global topology information to route data packets. Geographic routing requires the sources nodes to be aware of the location of sinks. Most existing geographic routing protocols merely assume that source nodes are aware of the locations of sinks. How can source nodes get the locations of sinks was not addressed in detail. In this paper, we propose a sink location service via circle path for geographic routing in wireless sensor networks. In this scheme, a sink sends a Sink Location Announcement (SLA) message along a circle path, and a source node sends a Sink Location Query (SLQ) message along a straight path that certainly passes through the circle path. By this way we can guarantee the SLQ path and SLA path have at least one crossing point. The node located on the crossing point of the two paths informs the source node the sink location. This procedure can correctly work in any irregular profile sensor networks such as network that has holes or irregular shape by some rules. Simulation results show that our protocol is superior to other protocols in terms of energy consumption and control overhead.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.4
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• pp.299-304
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• 2017

A wireless passive sensor network is a network consisting of sink nodes, sensor nodes, and radio frequency (RF) sources, where an RF source transfers energy to sensor nodes by radiating RF waves, and a sensor node transmits data by consuming the received energy. Against theoretical expectations, a wireless passive sensor network suffers from many practical difficulties: scarcity of energy, non-simultaneity of energy reception and data transmission, and inefficiency in allocating time resources. Perceiving such difficulties, we propose a simple contending-type medium access control (MAC) scheme for many sensor nodes to deliver packets to a sink node. Then, we derive an approximate expression for the network-wide throughput attained by the proposed MAC scheme. Also, we present an approximate expression for the optimal partition, which maximizes the saturated network-wide throughput. Numerical examples confirm that each of the approximate expressions yields a highly precise value for network-wide throughput and finds an exactly optimal partition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12A
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• pp.994-1005
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• 2011

In this paper, we propose a novel approach to optimize the movement of mobile sink node, called AMSP(Adaptive Mobile Sink Path) for mobile sensor network environments. Currently available studies usually suffer from unnecessary data transmission resulting from random way point approach. To address the problem, we propose a method which uses the Hilbert curve to create a path. The proposed method guarantees shorten transmission distance between the sink node and each sensor node by assigning orders of the curve according to sensor node density. Furthermore, The schedule of the sink node is informed to all of the sensing nodes so that the Duty Cycle helps the network be more energy efficient. In our experiments, the proposed method outperforms the existing works such as TTDD and CBPER by up to 80% in energy consumption.

• Journal of KIISE:Information Networking
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• v.35 no.2
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• pp.120-129
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• 2008

The purpose of sensor network is gathering the information from sensor nodes. If there are selfish node that deliberately avoid packet forwarding to save their own energy, the sensor network has trouble to collect information smoothly. To solve this problem we suggest a mechanism which uses credit payment schema according to the amount of forwarding packets. Sensor nodes use credits to send their own message and they forward packets of other sensor nodes to get credits. To offer authenticity we combined the roles of sink node and server, also we used piggybacking not to send additional report message. The packet trace route is almost fixed because sensor node doesn't have mobility. In this case, it happens that some sensor nodes which don't receive forwarding packets therefore they can't get credit. So, we suggested the way to give more credits to these sensor nodes. Finally, we simulated the suggested mechanism to evaluate performance with ns2(network simulator). As a result, packet transmission rate was kept on a high rate and the number of arrival packets to sink node was increased. Also, we could verify that more sensor nodes live longer due to deceasing the energy consumption of sensor nodes.

• Journal of the Korea Society for Simulation
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• v.17 no.1
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• pp.1-8
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• 2008

If a sink can move in sensor networks, the routing change can be more occur. If the sink has the mobility, it moves in sensor network area so that the connection between the sink system and sensor nodes will be changed continuously. Hence, the overhead can occur cased by the many routing changed. Therefore, the dynamic routing scheme is needed to support the mobile sink connection. In this paper, we propose the previous connection assignment scheme. The mobile sink can have low cost overhead from calculating dynamic rerouting that it determines the new virtual path before the physical path setup.

• International Journal of Computer Science & Network Security
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• v.21 no.3
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• pp.212-218
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• 2021

Low-power and Lossy Networks (LLNs) have become the common network infrastructure for a wide scope of Internet of Things (IoT) applications. For efficient routing in LLNs, IETF provides a standard solution, namely the IPv6 Routing Protocol for LLNs (RPL). It enables effective interconnectivity with IP networks and flexibly can meet the different application requirements of IoT deployments. However, it still suffers from different open issues, particularly in large-scale setups. These include the node unreachability problem which leads to increasing routing losses at RPL sink nodes. It is a result of the event of memory overflow at LLNs devices due to their limited hardware capabilities. Although this can be alleviated by the establishment of multi-sink topologies, RPL still lacks the support for effective load balancing among multiple sinks. In this paper, we address the need for an efficient multi-sink load balancing solution to enhance the performance of PRL in large-scale scenarios and alleviate the node unreachability problem. We propose a new RPL objective function, Multi-Sink Load Balancing Objective Function (MSLBOF), and introduce the Memory Utilization metrics. MSLBOF enables each RPL node to perform optimal sink selection in a way that insure better memory utilization and effective load balancing. Evaluation results demonstrate the efficiency of MSLBOF in decreasing packet loss and enhancing network stability, compared to MRHOF in standard RPL.