• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.1
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• pp.1-21
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• 2013

The release of IEEE 802.15.4e specification significantly develops IEEE 802.15.4. The most inspiring improvement is the enhancement for medium access control (MAC) sublayer. To study the performance of IEEE 802.15.4e MAC, in this paper we first present an overview of IEEE 802.15.4e and introduce three MAC mechanisms in IEEE 802.15.4e. And the major concern here is the Time Slotted Channel Hopping (TSCH) mode that provides deterministic access and increases network capacity. Then a detailed analytical Markov chain model for TSCH carrier sense multiple access with collision avoidance (CSMA-CA) is presented. Expressions which cover most of the crucial issues in performance analysis such as the packet loss rate, energy consumption, normalized throughput, and average access delay are presented. Finally the performance evaluation for the TSCH mode is given and we make a comprehensive comparison with unslotted CSMA-CA in non-beacon enabled mode of IEEE 802.15.4. It can validate IEEE 802.15.4e network can provide low energy consumption, deterministic access and increase network capacity.

• 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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.278-283
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• 2000

As information communication technology developed we could check our blood pressure, pulsation electrocardiogram, SpO2 and blood test easily at home. To check our health at ordinary times is able though interlocking the house medical instrument with the wireless public data network This service will help the inconvenience to visit the hospital everytime and will save the individual's time and cost. In each house an organism data which is detected from the human body will be transmitted to the distance hospital and will be essentially applied through wireless public data network The medical information transmit system is utilized by wireless close range network It would transmit the obtained organism signal wirelessly from the personal device to the main center system in the hospital. Remote telemetry system is embodied by utilizing wireless media access protocol. The protocol is embodied by grafting CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) protocol falling mode which is standards from IEEE 802.11. Among the house care telemetry system which could measure blood pressure, pulsation, electrocardiogram, SpO2 the study embodies the ECC(electrocardiograph) measure part. It within the ECC function into the movable device and add 900㎒ band wireless public data interface. Then the aged, the patients even anyone in the house could obtain ECG and keep, record the data. It would be essential to control those who had a health-examination heart diseases or more complicated heart diseases and to observe the latent heart disease patient continuously. To embody the medical information transmit system which is based on wireless network. It would transmit the ECG data among the organism signal data which would be utilized by wireless network modem and NCL(Native Control Language) protocol to contact through wireless network Through the SCR(Standard Context Routing) protocol in the network it will be connected to the wired host computer. The computer will check the recorded individual information and the obtained ECC data then send the correspond examination to the movable device. The study suggests the medical transmit system model utilized by the wireless public data network.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.741-753
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• 2008

This paper explores the throughput performance of CSMA/CA-based DCF protocol over both ideal channels and fading channels with payload size at the MAC layer in the 802.11a wireless LAN. In the ideal channel, there are no errors and at the transmission cycle there is one and only one active station which always has a packet to send and other stations can only accept packets and provide acknowledgements. In the fading channel, bit errors appear in the channel randomly and the number of stations is assumed to be fixed. And each station always has packets for transmission. In other words, we operate in saturation conditions. Up to now conventional research work about DCF throughput analysis of IEEE 802.11 a wireless LAN has been done over the ideal channel, but this paper is done over the Rayleigh/Ricean fading channel. So, the ratio of received average energy per bit-to-noise power spectral density $E_b/N_o$ is set to 25 dB and the ratio of direct-to-diffuse signal power in each sub-channel $\xi$ is set to 6 for combined Rayleigh/Ricean fading channel. In conclusion, it is shown that the saturation throughput is always less than the maximum throughput at all the payload size and the higher the transmission rate be, the higher the decreasing rate of saturation throughput compared to the maximum throughput be.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.24-29
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• 2006

본 논문에서는 광대역 통신 방송 융합 서비스 제공을 고려한 WDM 메트로 링 망을 위한 매체 접근 제어(Medium Access Control; MAC) 프로토콜의 성능을 분석한다. 현재 인터넷은 통신 방송 융합 망으로 진화하고 있으며 다양한 트래픽 특성을 갖는 서비스가 액세스 망에서 메트로 망으로 유입되고 있다. 그러나 기존 메트로 망의 MAC 프로토콜은 이러한 망 환경 변화를 고려하지 않고 단순하고 동일한 트래픽만을 고려하여 성능을 분석하였다. 따라서 본 논문에서는 메트로 링에 연결된 액세스 노드의 입력 트래픽을 Self-Similar와 Poisson 트래픽으로 분류하여 기존 MAC 프로토콜의 성능을 분석하고 평가한다. 메트로 링 망에 연결된 액세스 노드는 이 두 종류의 트래픽 중에서 하나를 망에 유입하며 채널을 공유하는 노드 수에 따라서 다양한 트래픽 환경이 고려된다. WDM 메트로 링망의 기본 MAC 프로토콜은 CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance)이며, 패킷을 빈 슬롯에 전송하고 송신지에서 패킷을 제거하는 SS (Source-Stripping) 기반으로 운용된다. 본 논문에서는 SS 방식으로 생성된 빈 슬롯을 바로 패킷 전송에 이용하는 방식과 그렇지 않은 방식을 각각 1-Persistent와 non-Persistent로 분류하고 MAC 프로토콜을 분석하여 기존 방식의 장 단점을 비교한다. 또한 전송 공정성과 처리율을 같이 고려하여 적용할 수 있는 확률 기반 p-Persistent MAC 프로토콜도 분석하였으며 시뮬레이션을 통하여 각 프로토콜을 노드 처리율, 전송 지연, 패킷 손실률, 전송 공정성 관점에서 비교하고 평가한다.y 수행을 여러 서버로 분산처리하게 함으로써 성능에 대한 신뢰성을 향상 시킬 수 있는 Load Balancing System을 제안한다.할 때 가장 효과적인 라우팅 프로토콜이라고 할 수 있다.iRNA 상의 의존관계를 분석할 수 있었다.수안보 등 지역에서 나타난다 이러한 이상대 주변에는 대개 온천이 발달되어 있었거나 새로 개발되어 있는 곳이다. 온천에 이용하고 있는 시추공의 자료는 배제하였으나 온천이응으로 직접적으로 영향을 받지 않은 시추공의 자료는 사용하였다 이러한 온천 주변 지역이라 하더라도 실제는 온천의 pumping 으로 인한 대류현상으로 주변 일대의 온도를 올려놓았기 때문에 비교적 높은 지열류량 값을 보인다. 한편 한반도 남동부 일대는 이번 추가된 자료에 의해 새로운 지열류량 분포 변화가 나타났다 강원 북부 오색온천지역 부근에서 높은 지열류량 분포를 보이며 또한 우리나라 대단층 중의 하나인 양산단층과 같은 방향으로 발달한 밀양단층, 모량단층, 동래단층 등 주변부로 NNE-SSW 방향의 지열류량 이상대가 발달한다. 이것으로 볼 때 지열류량은 지질구조와 무관하지 않음을 파악할 수 있다. 특히 이러한 단층대 주변은 지열수의 순환이 깊은 심도까지 가능하므로 이러한 대류현상으로 지표부근까지 높은 지온 전달이 되어 나타나는 것으로 판단된다.의 안정된 방사성표지효율을 보였다. $^{99m}Tc$-transferrin을 이용한 감염영상을 성공적으로 얻을 수 있었으며, $^{67}Ga$-citrate 영상과 비교하여 더 빠른 시간 안에 우수한 영상을 얻을 수 있었다. 그러므로 $^{99m}Tc$-transierrin이 감염 병소의 영상진단에 사용될 수 있을 것으로 기대된