• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.1
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• pp.24-30
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• 2006

The Controller Area Network (CAN) is being widely used for real-time control application and small-scale distributed computer controller systems. When the stuff bits are generated by bit-stuffing mechanism in the CAN network, it causes jitter including variations in response time and delay In order to eliminate this jitter, stuff bits must be controlled to minimize the response time and to reduce the variation of data transmission time. This paper proposes the method to reduce the stuff bits by restriction of available identifier and bit mask using exclusive OR operation. This da manipulation method are pretty useful to the real-time control strategy with respect to performance. However, the CAN may exhibit unfair behavior under heavy traffic conditions. When there are both high and low priority messages ready for transmission, the proposed precedence priority filtering method allows one low priority message to be exchanged between any two adjacent higher priority messages. In this way, the length of each transmission delays is upper bounded. These procedures are implemented as local controllers for the ISHURO(Inha Semvung Humanoid Robot).

• Journal of the Korea Society of Computer and Information
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• v.18 no.2
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• pp.1-8
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• 2013

TIn this paper, we propose a high performance L1 cache structure on the high clock CPU of 4GHz. The proposed cache memory consists of three parts, i.e., a direct-mapped cache to support fast access time, a two-way set associative buffer to exploit temporal locality, and a buffer-select table. The most recently accessed data is stored in the direct-mapped cache. If a data has a high probability of a repeated reference, when the data is replaced from the direct-mapped cache, the data is selectively stored into the two-way set associative buffer. For the high performance and low power consumption, we propose an one way among two ways set associative buffer is selectively accessed based on the buffer-select table(BST). According to simulation results, Energy $^*$ Delay product can improve about 45%, 70% and 75% compared with a direct mapped cache, a four-way set associative cache, and a victim cache with two times more space respectively.

• International Journal of Highway Engineering
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• v.14 no.2
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• pp.175-181
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• 2012

Under unsaturated capacity conditions with balanced approach flows, roundabout gives less delay and queue length than existing signalized intersections; however, over capacity conditions with unbalanced approach flows(flow above 450 pcu/h/lane), roundabouts efficiency drops due to the short gap between entering vehicles and circulating vehicles. This study provides a roundabout Signal Metering transfer standard and operation method. In this study, a four-way-approach with one-lane roundabout is selected to compare the Signal Metering performance for the case of unbalanced flow conditions. The performance is evaluated by using SIDRA software in terms of average delay and queue length. The result shows that the Signal Metering provides substantial improvements for the case of total approach flow is 1,800~2,000 pcu/h in which the main approach flow ratio is 60~70% gives 30~40% less delay and 30~60% less queue length than normal roundabout operation. Also, it is approved that operational performance saving can be achieved when the Metered Approach is selected adjoining to the main approach in pair.

• The Journal of the Korea Contents Association
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• v.8 no.8
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• pp.57-64
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• 2008

In this paper, to resolve the problem caused by a network state information inaccuracy the slow delay time that conclusion of network state of one way delay time which accuracy delay time information, according to network state changes on the based TFRC flow control, and suggest that flow control mechanism to adjust transfer rate fit of real time multimedia data. In simulation, to measure of netowork state information that on the average about 12% difference of compared RTT and $OWD{\times}2$. When used RTT, used fair bandwidth TFRC much better than TCP about 32%, when used OWD, difference about 3% used fair bandwidth. Thus, conclusion of accuracy network state that used fair bandwidth according to network state changes on the based TFRC, users can support service of high quality that flow control mechanism to adjust transfer rate fit of real time data.

• KIISE Transactions on Computing Practices
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• v.21 no.11
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• pp.727-732
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• 2015

These days, many researchers are working on Future Internet and a new networking paradigm called Software Defined Networking draws a great attention. In this paper, we redefine Software Defined Networking as Service Defined Networking which means that packets are categorized according to types of services. By using Service Defined Networking, we are not only dealing with the way to utilize the network resources efficiently but we also propose an algorithm to minimize the waiting time for packets to be delivered. This proposed algorithm can solve the delay problem, one of the most significant problems caused by network congestion. Also, since we are adopting Service Defined Networking, network resource utilization can be improved compared to the existing network.

• International Journal of Computer Science & Network Security
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• v.24 no.2
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• pp.178-188
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• 2024

In the near future, it is expected that there will be billions of connected devices using fifth generation (5G) network services. The recently available base stations (BSs) need to mitigate their loads without changing and at the least monetary cost. The available spectrum resources are limited and need to be exploited in an efficient way to meet the ever-increasing demand for services. Device to Device communication (D2D) technology will likely help satisfy the rapidly increasing capacity and also effectively offload traffic from the BS by distributing the transmission between D2D users from one side and the cellular users and the BS from the other side. In this paper, we propose to apply D2D overlay communication with cognitive radio capability in 5G networks to exploit unused spectrum resources taking into account the dynamic spectrum access. The performance metrics; throughput and delay are formulated and analyzed for CSMA-based medium access control (MAC) protocol that utilizes a common control channel for device users to negotiate the data channel and address the contention between those users. Device users can exploit the cognitive radio to access the data channels concurrently in the common interference area. Estimating the achievable throughput and delay in D2D communication in 5G networks is not exploited in previous studies using cognitive radio with CSMA-based MAC protocol to address the contention. From performance analysis, applying cognitive radio capability in D2D communication and allocating a common control channel for device users effectively improve the total aggregated network throughput by more than 60% compared to the individual D2D throughput without adding harmful interference to cellular network users. This approach can also reduce the delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.1
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• pp.224-240
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• 1996

It is common sense for at least one or more levels of cache memory to be used in these day's computer systems. In this paper, the impact of the internal cache memory organization on the performance of the computer is investigated by using a simulator program, which is wirtten by authors and run on SUN SPARC workstation, with several real execution, with several real execution trace files. 280 cache organizations have been simulated using n-way set associative mapping and LRU(Least Recently Used) replacement algorithm with write allocation policy. As a result, 16-way setassociative cache is the best configuration, and when we select 256KB cache memory and 64 byte line size, the bus traffic ratio was decreased compared to that of the noncache system so that a single bus could support almost 7 processors without any delay and degradationof high ratio(hit ratio was 99.21%). The smaller the line size we choose, the little lower hit ratio we can get, but the more processors can be supported by a single bus(maximum 18 processors). Therefore, using a proper cache memory organization can make a single bus structure be able to support multiple processors without any performance degradation.

• Journal of Satellite, Information and Communications
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• v.8 no.3
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• pp.25-31
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• 2013

In this paper, a new interleaving method for spatially-multiplexed multi-input-multi-output (SM-MIMO) scheme in an integrated mobile satellite and terrestrial system is proposed. In the proposed scheme, the transmitted bits for satellite path are interleaved in an innovative way to make sure that bits multiplied with different channel gains will be located alternatively in one received codeword after demapping, in order to compensate the performance degradation due to high-correlation of the satellite path. In addition, the interleaver can be implemented in a computationally efficient way and with the minimum time delay.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.75-83
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• 2016

In this paper, we propose a multi-channel medium access control (MAC) protocol, named underwater multi-channel MAC protocol (UMMAC), for underwater acoustic networks (UANs). UMMAC is a split phase and reservation based multi-channel MAC protocol which enables hosts to utilize multiple channels via a channel allocation and power control algorithm (CAPC). In UMMAC, channel information of neighboring nodes is gathered via exchange of control packets. With such information, UMMAC allows for as many parallel transmissions as possible while avoiding using extra time slot for channel negotiation. By running CAPC algorithm, which aims at maximizing the network's capacity, users can allocate their transmission power and channels in a distributed way. The advantages of the proposed protocol are threefold: 1) Only one transceiver is needed for each node; 2) based on CAPC, hosts are coordinated to negotiate the channels and control power in a distributed way; 3) comparing with existing RTS/CTS MAC protocols, UMMAC do not introduce new overhead for channel negotiation. Simulation results show that UMMAC outperforms Slotted floor acquisition multiple access (FAMA) and multi-channel MAC (MMAC) in terms of network goodput (50% and 17% respectively in a certain scenario). Furthermore, UMMAC can lower the end-to-end delay and achieves a lower energy consumption compared to Slotted FAMA and MMAC.

• Journal of Korean Society of Transportation
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• v.32 no.3
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• pp.218-226
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• 2014

This study examines a way to install a crosswalk that can improve pedestrians' convenience and safety and that goes beyond the crosswalk design standard of existing roundabouts. When a scrambled crosswalk, one of the crosswalk installation methods, is introduced to the roundabout system, it shortens the cross-walking distance of pedestrians and thus enhances convenience. Although the installation of a scrambled crosswalk may enhance pedestrians' convenience, it may obstruct vehicular traffic. Thus, this study presents standards for reasonable diagonal crosswalk installation based on the investigation on its effects on a vehicle's delay time. This study includes an analysis of the various geometric structures of roundabouts. The study results show that as v/c and the number of pedestrians increased, the delay time after the installation of a scrambled crosswalk increased although the extent was different. In general, the effect of the installation of a scrambled crosswalk was insignificant regardless of the number of pedestrians when v/c was under 0.6. When the number of pedestrians was 300/hour or lower, the difference in the delay time was quite insignificant regardless of v/c. In addition, as the inscribed circle of the roundabout was larger, the difference in the delay time decreased depending on v/c and the number of pedestrians.