• KSII Transactions on Internet and Information Systems (TIIS)
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• v.3 no.4
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• pp.344-365
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• 2009

The performance of a tracking system is greatly increased if multiple types of sensors are combined to achieve the objective of the tracking instead of relying on single type of sensor. To conduct the multi-modal tracking, we have previously developed a multi-modal sensor-based tracking model where acoustic sensors mainly track the objects and visual sensors compensate the tracking errors [1]. In this paper, we find a network synchronization problem appearing in the developed tracking system. The problem is caused by the different location and traffic characteristics of multi-modal sensors and non-synchronized arrival of the captured sensor data at a processing server. To effectively deliver the sensor data, we propose a time-based packet aggregation algorithm where the acoustic sensor data are aggregated based on the sampling time and sent to the server. The delivered acoustic sensor data is then compensated by visual images to correct the tracking errors and such a compensation process improves the tracking accuracy in ideal case. However, in real situations, the tracking improvement from visual compensation can be severely degraded due to the aforementioned network synchronization problem, the impact of which is analyzed by simulations in this paper. To resolve the network synchronization problem, we differentiate the service level of sensor traffic based on Weight Round Robin (WRR) scheduling at the routers. The weighting factor allocated to each queue is calculated by a proposed Delay-based Weight Allocation (DWA) algorithm. From the simulations, we show the traffic differentiation model can mitigate the non-synchronization of sensor data. Finally, we analyze expected traffic behaviors of the tracking system in terms of acoustic sampling interval and visual image size.

• The Journal of Korean Association of Computer Education
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• v.10 no.5
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• pp.81-88
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• 2007

To support the movement of a mobile network consisting of several mobile nodes, the IETF NEMO working group proposed NEMO basic support protocol using bi-directional tunneling between the home agent and the mobile router. Since NEMO basic support protocol is based on bi-directional tunneling, all communications to and from mobile nodes are suffer from inefficient routing all the cases. To solve the routing inefficiency problem, several proposals are proposed. However, those proposals results in new problems, such as binding update storm and changes in existing protocol. Especially, binding update storm problem may cause the delay in binding update, this subsequently causes the difficulty for a real time service and the handoff delay on the movement of mobile network. In this paper, we propose a new binding update scheme which reduces binding update latency and the handoff delay through the distribution of the transmission time of binding update messages. The performance of the proposed scheme is also evaluated to demonstrate its efficiency. Simulation results show that the proposed scheme can efficiently reduce the binding update latency.

• The KIPS Transactions:PartC
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• v.12C no.3 s.99
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• pp.409-418
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• 2005

This paper presents an efficient multicast method based on a locality in mobile IPv6 networks. We exploit the repetitive movement pattern of mobile node to reduce the total number of experience of graft and join procedure. We defined the locality scope by a movement pattern. While the network is included in the locality scope, the network should maintain a multicast tree even when the mobile node moves to the other network. In this way, the mobile host can receive a multicast service without a delay when it moves to the network in the locality scope later. We compare our scheme with existing schemes under the total signaling cost and the service delay time by using a discrete analytical model for cost analysis. Analytical results demonstrated that the total signaling cost and service delay time was significantly reduced through our proposed scheme.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.611-625
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• 2018

With innovative advances in wireless communication technology, many researches for extending network lifetime in maximum by using energy harvesting have been actively performed on the area of network resource optimization, QoS-guaranteed transmission, energy-intelligent routing and etc. As known well, it is very hard to guarantee end-to-end network delay due to uncertainty of the amount of harvested energy in multi-hop RF(radio frequency) energy harvesting wireless networks. To minimize end-to-end delay in multi-hop RF energy harvesting networks, this paper proposes an energy efficient routing metric based on interference aware and protocol which takes account of various delays caused by co-channel interference, energy harvesting time and queuing in a relay node. The proposed method maximizes end-to-end throughput by performing avoidance of packet congestion causing load unbalance, reduction of waiting time due to exhaustion of energy and restraint of delay time from co-channel interference. Finally simulation results using ns-3 simulator show that the proposed method outperforms existing methods in respect of throughput, end-to-end delay and energy consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8B
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• pp.716-729
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• 2003

As the public Internet and private internet have grown from small networks into large infrastructures, the need to more systematically manage the large number of network components within these networks has grown more important as well. The rapid growth of network size has brought into question the salability of the existing centralized model, such as SNMP(Simple Network Management Protocol) and CMIP(Common Management Information Protocol). Thus, for efficient network management, researches about mobile agent have also been performed recently. This paper presents analytical models of centralized approach based on SNMP protocol, distributed approach based on mobile agent, and mixed mode to make up for shortcomings of SNMP and mobile agent. We compare the performance of these analytical models based on network management response time. Experiment results show that performance of mobile agent and the nixed mode is less sensitive to the delay in WAN network environment. However, SNMP is more efficient for the simple network environment like LAN. We also propose an adaptive network management algorithm in consideration of network t environment. delay, task, and the number of nodes based on the results of analytical models. The results show that the adaptive network management algorithm can reduce the network management response time by 10% compared with either mobile agent or mixed mode network management algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.1377-1399
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• 2020

In search and rescue mission, micro aerial vehicles (MAVs) are typically used to capture image and video from an aerial perspective and transfer the data to the ground station. Because of the power limitation, a cluster of MAVs are required for a large search area, hence an ad-hoc wireless network must be maintained to transfer data more conveniently and fast. However, the unstable link and the intermittent connectivity between the MAVs caused by MAVs' movement may challenge the packet forwarding. This paper proposes a delay tolerant packet forwarding algorithm based on location estimation for MAV networks, called DTN_est algorithm. In the algorithm, ferrying MAVs are used to transmit data between MAVs and the ground station, and the locations of both searching MAVs and ferrying MAVs are estimated to compute the distances between the MAVs and destination. The MAV that is closest to the destination is selected greedy to forward packet. If a MAV cannot find the next hop MAV using the greedy strategy, the packets will be stored and re-forwarded once again in the next time slot. The experiment results show that the proposed DTN_est algorithm outperforms the typical DTN_geo algorithm in terms of packet delivery ratio and average routing hops.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.14 no.4
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• pp.295-304
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• 2014

Communication infrastructure supports wide variety of mobile services such as photo and file sharing, location tracking, social network services and instant messaging. However, instances like power-loss and natural disasters disrupt these communication infrastructures unable to render support to these mobile services. Delay-tolerant networks (DTNs) offer a solution to these problems at hand. By utilizing mobility and opportunistic contacts among mobile devices, a plausible communication network can be establish and enable support to mobile applications. This paper presents an energy-efficient, reliable message delivery routing scheme with message prioritization rules for DTN. It uses the context information of nodes (mobile devices) such as the contact history (location and time of contact), speed/velocity, moving direction to determine the best forwarders among nodes in the network. The remaining energy of the nodes is also used to determine the message types a node can deliver successfully. The simulation results show that proposed approach outperforms Epidemic and Prophet routing schemes in terms of delivery ratio, overhead ratio, delivered messages per types and remaining energy.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.53-58
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• 2019

This paper proposes a class-based FQ-CoDel(Flow Queue-Control Delay) algorithm. A variety of application system services create bottlenecks in tactical communication network and the bottlenecks cause some problems such as traffic loss and delay. Therefore, more research on effective traffic processing is needed. The proposed class-based FQ-CoDel algorithm, suggests dynamic buffer management and scheduling, classifies specific packets in each queue according to service attribute and criticality and checks periodically latency of the packets in each queue. Also, it abandons the packets if some packets stay in queue above schedule time and manages the total amount of traffic stored in queue with certain level.

• Journal of Information Processing Systems
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• v.2 no.2
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• pp.76-81
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• 2006

A PDA is used mainly for downloading data from a stationary server such as a desktop PC in an infrastructure network based on wireless LAN. Thus, the overall performance depends heavily on the performance of such downloading with PDA. Unfortunately, for a PDA the time taken to receive data from a PC is longer than the time taken to send it by 53%. Thus, we measured and analyzed all possible factors that could cause the receiving time of a PDA to be delayed with a test bed system. There are crucial factors: the TCP window size, file access time of a PDA, and the inter-packet delay that affects the receiving time of a PDA. The window size of a PDA during the downstream is reduced dramatically to 686 bytes from 32,581 bytes. In addition, because flash memory is embedded into a PDA, writing data into the flash memory takes twice as long as reading the data from it. To alleviate these, we propose three distinct remedies: First, in order to keep the window size at a sender constant, both the size of a socket send buffer for a desktop PC and the size of a socket receive buffer for a PDA should be increased. Second, to shorten its internal file access time, the size of an application buffer implemented in an application should be doubled. Finally, the inter-packet delay of a PDA and a desktop PC at the application layer should be adjusted asymmetrically to lower the traffic bottleneck between these heterogeneous terminals.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.121-126
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• 2018

IEEE 802.1 TSN TG is developing standards for end-to-end delay bounds and zero packet loss based on Ethernet technology. We focus on packet forwarding techniques. TSN packet forwarding techniques can be classified into Synchronous and Asynchronous framework. Synchronous approach allocates fixed time period for a class, yet is complex for large networks. Asynchronous approach provides delay guarantee by regulator-scheduler pair, yet is unnecessarily complex, too. We propose network components for TSN Asynchronous architecture, which remove the complexity of maintaining flow state for regulation decisions. Despite such a simplicity, the proposed architecture satisfies the TSN's delay requirements provided the limited high priority traffic's maximum packet length.