• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.37 no.2
• /
• pp.17-23
• /
• 2000

Wireless link has high bit error rate compared with wired link and many users share this limited bandwidth. So it needs more powerful error control code and efficient media access control(MAC) to provide multimedia service reliably. In this paper we proposed efficient MAC frame format based on TDMA using mini-slot for request access. The number of mini-slots is variable based on the result of collision in the previous frame. This dynamic allocation of request mini-slots helps resolve the contention situation quickly and avoids the waste of bandwidth that may occur when there are several unneeded request mini-slots. The simulation results are also presented in terms of channel utilization, call blocking probability and cell transmission delay for mixed traffic environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.2
• /
• pp.426-430
• /
• 2005

The computer practicing class advances to reach the ultimate goal of learning through the comprehensive learning of theory. Moreover, the improved function and environment of computer makes it easy for students to access a variety of information. However, students are likely to get into the internet and other things mainly for fun during the computer practicing class, and the multi-tasking may distract the concentration of students and degrade their performance. Computers for practice purpose need to be controlled to minimize such distraction. In this dissertation, we monitor and control computers which are used by students for the purpose of practicing, realize the function of transfer and deletion of file, whole shutdown of computer and screen capture. We also applied the class based on current way and realized program, and assigned the practice work on the basis of what was learned during the class. We intend to understand the relation between the concentration of students and their performance by assigning practice work related to survey after the class, capture file and log file

• Journal of the Institute of Electronics and Information Engineers
• /
• v.53 no.2
• /
• pp.10-16
• /
• 2016

For higher reliability against a link failure of a control network in railway vehicles, a recovery mechanism is needed. We introduce a problem that, when a link failure occurs in a ring-topology control network, a node may experience a significant increase of transmission delay depending on its relative position within the network. We then propose two mechanisms to solve this problem: (1) differentiating and prioritizing node traffic in forwarding; and (2) switching some nodes to a backup bus-topology network. Our simulation study shows that, while the first mechanism achieves a limited gain by only compensating queuing delay, the second one gets a sufficient gain which is impacted by the number of nodes switched to the bus network.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.35S no.11
• /
• pp.44-52
• /
• 1998

In this paper, we proposed a node architecture and cell routing strategies for ATM applications in WDM multihop networks. The proposed node architecture employs the optical delay loop for storing the cell which is failed in out-link contention. This optical delay loop allows the delay of one cell without the electro-optic conversion. Therefore, we can get the advantages of S&F(Store-and-Forward) routing in Deflection-based all-optical networks. To support the ATM applications efficiently. we considered the transmission priority of ATM cell so that high priority cell can be transmitted with lower loss and shorter delay than low priority one. Two kinds of routing strategies are designed for this architecture: Scheme-Ⅰand Scheme-Ⅱ. Scheme-Ⅰapplies S&F routing to high cell and Deflection routing to low cell, i.e., high cells are routed along the shortest path based on S&F routing, but low cells are deflected or lost. Schem-Ⅱ is similar to Scheme-Ⅰexcept that low cells can occupy the optical loop if it is available. This Scheme-Ⅱ increases the utilization of network resources without decreasing the throughput of high cell by reducing the low cell loss rate when traffic load is low. Simulation results show that our routing strategies have better performance than conventional ones under non-uniform traffic as well as uniform traffic.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.5 s.347
• /
• pp.84-93
• /
• 2006

Ethernet-PON is an emerging access network technology that provides a low-cost method of deploying optical access lines between OLT and ONUs. It has a point-to-multipoint and multipoint-to-point architecture in downstream and upstream direction, respectively. Therefore, downstream packets are broadcast from an OLT toward all ONUs sithout collision. On the other hand, since alt ONUs share a common channel, the collision may be occurred for the upstream transmission. Therefore, earlier efforts on Ethernet-PON have been concentrated on an upstream MAC protocol to avoid collision. But it is needed to control downstream traffic in practical access network, where the network provider limits available bandwidth according to the number of users. In this paper, we propose a traffic control scheme for supporting the fairness of the downstream bandwidth. The objective of this algorithm is to guarantee the fairness of ONUs while maintaining good performance. In order to do this, we define the service probability that considers the past traffic information for downstream, the number of tokens and the relative size of negotiated bandwidth. We develop the simulation model for Ethernet-PON to evaluate the rate-limiting algorithm by using AWESIM. Some results are evaluated and analyzed in terms of defined fairness factor, delay and dropping rate under various scenario.

• Journal of Biomedical Engineering Research
• /
• v.24 no.5
• /
• pp.411-419
• /
• 2003

This paper aims at developing 'gyro-mouse' which provides decent and comfortable human-computer interface that supports the usage of such software as an internet-browser in PC for the people paralyzed in upper limbs. This interface operates on information collected from head movement to get the cursor control. The interface is composed of two modules. One is hardware module in which the head horizontal and vertical angular velocities are detected and transmitted into PC. The other is a PC software that translates the received data into movement and click signals of the mouse. The ANN (artificial neural network) learns the quick nodding pattern of each user as click input so that it can provide user-friendly interface. The performance of the system was evaluated by three indices that are click recognition rate. error in cursor position control. and click rate of the moving target box. The performance result of the gyro-mouse was compared with that of the optical-mouse to assess the efficiency of the gyro-mouse. The average click recognition rate was 93%, average error in cursor position control was 1.4∼5 times of optical mouse. and the click rate with 50 pixels target box was 40%(30 clicks/min) to that of optical mouse. The click rate increased monotonously with the number of trial from 35% to 44%. The suggested system is expected to provide a new possibility to communicate with the society.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.40 no.10
• /
• pp.67-78
• /
• 2003

As optical network technology advances and high bandwidth Internet is demanded for the exponential growth of internet traffic volumes, the Dense-Wavelength Division Multiplexing (DWDM) networks have been widely accepted as a promising approach to the Next Generation Optical Internet (NGOI) backbone networks for nation wide or global coverage. Important issues in the NGOI based on DWDM networks are the Routing and Wavelength Assignment(RWA) problem and survivability. Especially, fault/attack detection, localization and recovery schemes in All Optical Transport Network(AOTN) is one of the most important issues because a short service disruption in DWDM networks carrying extremely high data rates causes loss of vast traffic volumes. In this paper, we suggest a fault/attack management model for NGOI through analyzing fault/attack vulnerability of various optical backbone network devices and propose fault/attack recovery procedure considering Extended-LMP(Link Management Protocol) and RSVP-TE+(Resource Reservation Protocol-Traffic Engineering) as control protocols in IP/GMPLS over DWDM.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.14 no.9
• /
• pp.1957-1964
• /
• 2010

In Video coding, the first frame is encoded in intra mode which generates a larger number of bits. In addition, the first frame is used for the inter mode encoding of the following frames. Thus the intial QP for the first frame of GOP affects the first frame as well as the following frames. Traditionally, the initial QP of a GOP is determined by the initial QP of the previous GOP and the average QP of the inter mode frames. In case of JM, the initial QP of a GOP is adjusted as the initial QP being less than the average QP of inter mode frames by two. However, this method is not suitable for the low bit rate video coding. In this paper, the linear relationship between the optimal QP and the ratio of the PSNR of the first frame and the average PSNR of the inter mode frames is first investigated and the linear model is proposed based on the results of the investigation. The proposed model calculate the optimal initial QP using the encoding results of the previous GOP. It is shown by experimental results that the new algorithm can predict the optimal initial QP more accurately and generate the PSNR performance better than that of the existing JM algorithm.

• Journal of the Korea Society of Computer and Information
• /
• v.7 no.4
• /
• pp.188-198
• /
• 2002

In this paper, we propose an active network to support reliable data transmission in the mobile ad-hoc network. The active network uses DSR(Dynamic Source Routing) protocol as its basic routing protocol, and uses source and destination nodes as key active nodes. For reliable improvement the source node is changed to source active node to add function that its buffer to store the last data with the flow control for data transmission per destination node. The destination node is changed to destination active node to add function that it requests the re-transmission for data that was not previously received by the destination active node with the flow control for data reception per source active node As the result of evaluation. we found the proposed active network guaranteed reliable data transmission with almost 100% data reception rate for slowly moving mobile ad-hoc network and with more 95% data reception rate, which is improvement of 3.5737% reception rate compared with none active network, for continuously fast moving mobile ad-hoc network.

• The Transactions of the Korea Information Processing Society
• /
• v.7 no.8
• /
• pp.2310-2326
• /
• 2000

Client-server DBMS based on a data-shipping model can exploit e1ient resources effectively by allowing inter-transaction caching. However, inter-transaction caching raises the need of transactional cache consistency maintenancetTCCM protocol. since each client is able to cache a portion of the database dynamically. Deferred locking(DL) is a new detection-based TCCM scheme designed on the basis of a primary copy locking algorithm. In DL, a number of lock ,ujuests and a data shipping request are combined into a single message packet to minimize the communication overhead required for consistency checking. Lsing a simulation model. the performance of the prolxlsed scheme is compared with those of two representative detection based schemes, the adaptive optimistic concurrency control and the caching two-phase locking. The performance results indicate that DL improves the overall system throughput with a reasonable transaction abort ratio over other detection - based schemes.