• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.433-436
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• 1998

Hot carrier induceed the performance degradation of sense amplifier circuit in DRAM has been measured and analyzed using 0.8.mu.m CMOS process. Simulation and experimental results show that the degradation of the MOS devices affects the decrease of the half-Vcc, voltage gain and the increase of the sensing voltage gain and the increase of the sensing voltage. The dominant degradation mechanism is the capacitance imblance in the bit-line pair. We carried out the spice simulation to investigate the degradation of the sense amplifier circuit.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.6
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• pp.1060-1064
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• 2006

Data collected by sensors in field are transmitted to the base station gathering all of data. Because sensors have to gather data in surroundings and periodically transmit data to the base station, it makes energy consumed much. In this paper, we mose the scheme that is to avoid traffic congestion with achievement of energy efficiency, so collected data is transmitted efficiently. This is to adjust transmission rate differently in case of increasing or decreasing traffic and minimize the energy consumption with setting ideal options up basic CSMA(Carrier Sense Multiple Access) protocol in each sensor. Through the simulation, we find the ideal CSMA options and apply the proposed scheme of traffic control mechanism to them and analyze them, then show energy efficiency and effective traffic control mechanism.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.95-98
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• 2006

Data collected by sensors in field are transmitted to the base station gathering all of data. Because sensors have to gather data in surroundings and periodically transmit data to the base station, it makes energy consumed much. In this paper, we propose the scheme that is to avoid traffic congestion with achievement of energy efficiency, so collected data is transmitted efficiently. This is to adjust transmission rate differently in case of increasing or decreasing traffic and minimize the energy consumption with setting ideal options up basic CSMA(Carrier Sense Multiple Access) protocol in each sensor. Through the simulation, we find the ideal CSMA options and apply the proposed scheme of traffic control mechanism to them, then show energy efficiency and effective traffic control mechanism.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.133.3-133
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• 2001

This paper analyses the real-time performance of Ethernet based intranet whether it is applicable to the real-time network. Unpredictability of transmission delay by collision-delay-retransmission mechanism in CAMA/CD(Carrier Sense Multiple Access with Collision Detect) of Ethernet is the major reason making hard to apply to real-time system. Both retransmission mechanism of TCP(Transmission Control Protocol) for reliability and sliding windows algorithm for high utilization make hard to predict transmission delay. Because real-time control network require fast responsibility and bustle of short-periodic messages, global-clock for collision avoidance and UDP(User Datagram Protocol) for high utilization of network are used. The mathematical models for time-delay that can be occured between ...

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1462-1476
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• 2017

The current literature on discrete-time Markov chain (DTMC) based analysis of IEEE 802.15.6 MAC protocols for wireless body area networks (WBANs), do not consider the ACK timeout state, wherein the colliding nodes check the ill fate of their transmissions, while other contending nodes perform backoff check that slot as usual. In this paper, our DTMC model accurately captures the carrier sense multiple access with collision avoidance (CSMA/CA) mechanism of IEEE 802.15.6 medium access control (MAC) and allows the contending nodes performing backoff to utilize the ACK timeout slot during collisions. The compared rigorous results are obtained by considering a non-ideal channel in non-saturation conditions, and CSMA/CA parameters pertaining to UWB PHY of IEEE 802.15.6 MAC protocols.

• Journal of Communications and Networks
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• v.12 no.1
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• pp.43-51
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• 2010

IEEE 802.11 defines distributed coordination function (DCF), which is characterized by CSMA/CA and binary exponential backoff (BEB) algorithm. Most modifications on DCF so far have focused on updating of the contention window (CW) size depending on the outcome of own frame transmission without considering freezing periods experienced in the backoff interval. We propose two simple but novel schemes which effectively utilize the number of freezing periods sensed during the current backoff interval. The proposed schemes can be applied to DCF and its family, such as double increment double decrement (DIDD). Saturation throughput of the proposed schemes is analyzed by means of Bianchi's Markovian model. Computer simulation validates the accuracy of the analysis. Numerical results based on IEEE 802.11b show that up to about 20% improvement of saturation throughput can be achieved by combining the proposed scheme with conventional schemes when applied to the basic access procedure.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.493-495
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• 2003

IEEE 802.11 DCF에서는 CSMA/CA(Carrier Sense Multiple Access/Collision Avoidance)를 통해 패킷들간의 충돌 확률을 줄여주고 있다. 하지만, 채널을 공유하는 station들이 증가할수록 충돌이 심해져 이를 해결하기 위해 많은 연구가 수행되고 있다. 그 대표적인 접근 방법으로 802.11 표준의 backoff 방식을 개선하거나, DCF+[3]처럼 Data­ACK (혹은 RTS­CTS­Data­ACK)의 기존의 프레임 교환 방식을 수정하여 한 번 전송에 성공한 station이 채널을 오랫동안 소유하여 채널의 활용도를 높이는 방법을 제안하고 있다. 본 논문에서는 기존의 방법들과는 다르게 성공하였을 때가 아니라 충돌이 발생하였을 때의 상황을 역으로 이용하여 무선망에서 공명성(fairness)를 높이는 새로운 방법을 제시하고 있다.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.89-90
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• 2006

In this paper, the performances of the IEEE 802.15.4 under the IEEE 802.11b interference are compared under two kinds of channel sensing mechanisms: carrier sense (CS) and energy detection (ED). For each channel sensing mechanism, the average transmission delay, and the throughput are used as performance measures.

• Journal of Communications and Networks
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• v.10 no.3
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• pp.287-296
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• 2008

The IEEE 802.11 wireless standard uses the carrier sense multiple access with collision avoidance (CSMA/CA) as its MAC protocol (during the distributed coordination function period). This protocol is an adaptation of the CSMA/CD of the wired networks. CSMA/CA mechanism cannot guarantee quality of service (QoS) required by the application because orits random access method. In this study, we propose a new MAC protocol that considers different types of traffic (e.g., voice and data) and for each traffic type different priority levels are assigned. To improve the QoS of IEEE 802.11 MAC protocols over a multi-channel CSMA/CA, we have developed a new admission policy for both voice and data traffics. This protocol can be performed in direct sequence spread spectrum (DSSS) or frequency hopping spread spectrum (FHSS). For voice traffic we reserve a channel, while for data traffic the access is random using a CSMA/CA mechanism, and in this case a selective reject and push-out mechanism is added to meet the quality of service required by data traffic. To study the performance of the proposed protocol and to show the benefits of our design, a mathematical model is built based on Markov chains. The system could be represented by a Markov chain which is difficult to solve as the state-space is too large. This is due to the resource management and user mobility. Thus, we propose to build an aggregated Markov chain with a smaller state-space that allows performance measures to be computed easily. We have used stochastic comparisons of Markov chains to prove that the proposed access protocol (with selective reject and push-out mechanisms) gives less loss rates of high priority connections (data and voices) than the traditional one (without admission policy and selective reject and push-out mechanisms). We give numerical results to confirm mathematical proofs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.5835-5854
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• 2017

The implementation of IEEE 802.15.6 in Wireless Body Area Network (WBAN) is contention based. Meanwhile, IEEE 802.15.4 MAC provides limited 16 channels in the Superframe structure, making it unfit for N heterogeneous nature of patient's data. Also, the Beacon-enabled Carrier-Sense Multiple Access/Collision-Avoidance (CSMA/CA) scheduling access scheme in WBAN, allocates Contention-free Period (CAP) channels to emergency and non-emergency Biomedical Sensors (BMSs) using contention mechanism, increasing repetition in rounds. This reduces performance of the MAC protocol causing higher data collisions and delay, low data reliability, BMSs packet retransmissions and increased energy consumption. Moreover, it has no traffic differentiation method. This paper proposes a Low-delay Traffic-Aware Medium Access Control (LTA-MAC) protocol to provide sufficient channels with a higher bandwidth, and allocates them individually to non-emergency and emergency data. Also, a Contention Differentiated Adaptive Slot Allocation CSMA-CA (CDASA-CSMA/CA) for scheduling access scheme is proposed to reduce repetition in rounds, and assists in channels allocation to BMSs. Furthermore, an On-demand (OD) slot in the LTA-MAC to resolve the patient's data drops in the CSMA/CA scheme due to exceeding of threshold values in contentions is introduced. Simulation results demonstrate advantages of the proposed schemes over the IEEE 802.15.4 MAC and CSMA/CA scheme in terms of success rate, packet delivery delay, and energy consumption.