• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.210-216
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• 2014

In this paper, it was proposed to develop front and rear image monitoring system for vehicle that help a driver to cope with urgent situation about a dangerous element. When parking a vehicle, the risk factors to be formed by the dead zone can be resolved by using anterior and posterior cameras of the vehicle. In embedded system environment, a SoC(System on Chip) and two high-resolution CMOS (Complementary metal-oxide-semiconductor) image sensors were used to transfer two high-resolution image data through he TCP/ IP-based network. To transfer image data through he TCP/ IP-based network, the images received by two cameras were compressed by using H.264 and they were transmitted with wireless method(Wi-Fi) by using real-time transport protocol (Real-time Transport Protocol). Transmission loss, transmission delay and transmission limit were solved in wireless (Wi-Fi) environment and the bit-rate of two image data compressed by H.264 was adjusted. And the system for the optimal transmission in wireless (Wi-Fi) environment was materialized and experimented.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.227-242
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• 2019

This paper presents a method to predict ground types ahead of a tunnel face utilizing operational data of the earth pressure-balanced (EPB) shield tunnel boring machine (TBM) when running through soil ground. The time series analysis model which was applicable to predict the mixed ground composed of soils and rocks was modified to be applicable to soil tunnels. Using the modified model, the feasibility on the choice of the soil conditioning materials dependent upon soil types was studied. To do this, a self-organizing map (SOM) clustering was performed. Firstly, it was confirmed that the ground types should be classified based on the percentage of 35% passing through the #200 sieve. Then, the possibility of predicting the ground types by employing the modified model, in which the TBM operational data were analyzed, was studied. The efficacy of the modified model is demonstrated by its 98% accuracy in predicting ground types ten rings ahead of the tunnel face. Especially, the average prediction accuracy was approximately 93% in areas where ground type variations occur.

• Journal of the Korea Society of Computer and Information
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• v.19 no.11
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• pp.9-15
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• 2014

In this paper, We propose a block reallocation algorithm for reducing network traffic in Hadoop cluster. The scheduler of Hadoop cluster receives a job from users. And the job is divided into multiple tasks assigned to nodes. At this time, the scheduler allocates the task to the node that satisfied data locality. If a task is assigned to the node that does not have the data(block) to be processed, the task is processed after the data transmission from another node. There is difference of workload among nodes because blocks in cluster have different access frequency. Therefore, the proposed algorithm relocates blocks according to the task allocation pattern of Hadoop scheduler. Eventually, workload of nodes are leveled, and the case of the task processing in a node that does not have the block to be processing is reduced. Thus, the network traffic of the cluster is also reduced. We evaluate the proposed block reallocation algorithm by a simulation. The simulation result shows maximum 23.3% reduction of network consumption than default delay scheduling for jobs processing.

• Journal of Korean Society of Transportation
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• v.26 no.1
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• pp.191-201
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• 2008

It has been employed TRANSYT-7F and NETSIM to evaluate the validity and effectiveness of improvement on TSM(Transportation Systems Management). But T7F is hard to describe platoon compression and dispersion in actually, and NETSIM takes a long time for network coding, calibration and have difficulty in setting up saturation flow. While Shockwave Model have advantage which can describe platoon compression and dispersion in actually and shorten hours, convenience of application. But Shockwave Model apply unrealistic traffic flow relation ship(U-K curve) and simplify platoon because of difficulty in calculating shockwave's position and cross. For solving limitation of existing shockwave models, It develop new model with 2-regime linear model, New platoon model, Extended shockwave, etc. For verifying the validity of the proposed model, it was compared with delay of T7F and NETSIM by offset variation. In conclusion, it is thought that proposed model have outstanding performance to simulate traffic phenomenon.

• Journal of KIISE:Information Networking
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• v.31 no.1
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• pp.91-100
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• 2004

This paper presents a receiver-driven TCP flow control mechanism, which is adaptive to the wireless condition, for memory constrained mobile receiver. A receiver-driven TCP flow control is, in general, achieved by adjusting the size of advertised window at the receiver. The proposed method constantly measures at the receiver both the available wireless bandwidth and the packet round-trip time. Depending on the measured values, the receiver adjusts appropriately the size of advertised window. Constrained by the adjusted window which reflects the current state of the wireless network, the sender achieves an improved TCP throughput as well as the reduced round-trip packet delay. Its implementation only affects the protocol stack at the receiver and hence neither the sender nor the router are required to be modified. The mechanism has been implemented in real environments. The experimental results show that in CDMA2000 1x networks the TCP throughput of the proposed method has improved about 5 times over the conventional method when the receiver's buffer size is limited to 2896 bytes. Also, with 64Kbytes of buffer site, the packet round-trip time of the proposed method has been reduced in half, compared the case with the conventional method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8A
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• pp.679-687
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• 2005

A mobile ad-hoc network (MANET) is one consisting of a set of mobile hosts capable of communicating with each other without the assistance of base stations. It is necessary to use bandwidth effectively because MANET has limited bandwidth. In this paper, we propose SMGS (source based multiple gateway selection routing protocol). In SMGS, each node estimates its expected life time (ELT) and if its ELT is larger than that of current gateway it becomes a candidate node. When a source node establishes a path, in each grid the candidate node will take the route request and be a gateway node for the each source node. The node that is expected to stay the longest time in the grid is selected so that we can reduce frequent gateway handoff, packet loss, and handoff delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12B
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• pp.1049-1057
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• 2006

Overlay Multicast is an effective method for efficient utilization of system resources and network bandwidth without using hardware customization. Unlike in IP multicast, multicast tree reconstruction is required when non-leaf node leaves or fails. In this paper, we propose a proactive approach to solve this defect by using a resource reservation of the out degrees. This allows children of non-leaf node to connect to its new parent node immediately when its parent node leaves or fails. In our proposal, a proactive route maintenance gives a fast recovery time and reduces a delay effect in the new route. The simulation results show that our proposal takes shorter period of time than the other algorithms to reconstruct a similar tree and that it is a more effective way to deal with a lot of nodes that have lost their parent nodes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.2
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• pp.307-312
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• 2000

Asynchronous transfer mode(ATM) is flexible to support the various multimedia communication services such as data, voice, and image by applying asynchronous time-sharing and statistical multiplexing techniques to the existing data communication. ATM service is categorized to CBR, VBR, UBR, and ABR according to characteristics of the traffic and a required service qualities. Among them, ABR service guarantees a minimal bandwidth and can transmit cells at a maximum transmission rate within the available bandwidth. To minimize the cell losses in transmission and switching, a feedback information in ATM network is used to control the traffic. In this paper, predictive control algorithms are proposed for the feedback information. When the feedback information takes a long propagation delay to the backward nodes, ATM switch can experience a congestion situation from the queue length increases, and a high queue length fluctuations in time. The control algorithms proposed in this paper provides predictive control model using slop changes of the queue length function and previous data of the queue lengths. Simulation shows the effectiveness result of the proposed control algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3B
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• pp.264-273
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• 2009

For IEEE 802.15.3 HR-WPAN, we propose the DABL algorithm that PNC can allocate the channel times to the DEV in super frame in order that system frame throughput is increased and the delay is decreased. In detail, the DABL algorithm allows to dynamically allocate channel time as well as to adaptively apply the modulation and coding scheme based on the link quality of the DEV. In addition, due to the facts that QoS is quite different depending on service types, we provide the DABL algorithm taking into account RT(Real Time) traffic and Non-RT traffic respectively. Finally, we show simulation results of the DABL algorithm compared to the conventional algorithm that the PNC equally allocates channel times to the DEV regardless of the link quality of the DEV.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.21-26
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• 2016

With the increased desire of TV consumers for interactivity and personalization, IPTV has been rapidly spread in recent years. IPTV can provide a variety of services through hundreds of channels, but the explosion of TV channels makes users even more difficult to find their desired contents. In addition, the channel zapping delay of IPTV is serious due to the limited network bandwidth. To resolve these problems, this paper distinguishes hot and cold channels by exploiting the real-time viewing rate as well as each user's viewing history, and then, maintains hot channels in the hot list, which is searched first during channel navigation and also prefetched to support the preview of channels. Experimental results show that the proposed scheme improves the IPTV channel seek time significantly compared to existing channel seeking interfaces.