• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.47-48
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• 2006

In this paper, we analyze the impact of superframe order on the performance of the IEEE 802.15.4 slotted CSMA/CA. A new analytic model to evaluate the saturation throughput is proposed. The new model describes slot time behaviors of the IEEE 802.15.4 slotted CSMA/CA. The proposed model is validated via the comparison with ns-2 simulation results.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.67-73
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• 2005

For power constrained applications, IEEE 802.15.4 networks may be operated in beacon enabled mode with inactive period. In this paper, we propose the Virtual Arrival Mechanism (VAM) to avoid the congestion at the beginning of each contention access period (CAP). Virtual Arrival Mechanism (VAM) is a kind of traffic shaping that spread the traffics congested at the beginning of CAP into the whole CAP. By using VAM, collisions and energy consumption can be reduced. Finally, we evaluate the performance enhancement of VAM using NS-2 simulator.

• Journal of Korea Multimedia Society
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• v.11 no.6
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• pp.835-844
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• 2008

ZigBee devices are limited in resources especially on power and computational capacity but also require real-time operation at MAC layer. Therefore, it is important to take those requirement into consideration of system software design. In this paper, we proposed a compact system software design to support simultaneously ZigBee and IEEE802.15.4. The design strictly respects the resource and real-time constraints while being optimized for specific functions of both Zigbee and IEEE802.15.4. Various evaluations are done to show significant metrics of our design.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1136-1139
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• 2009

본 논문은 802.15.4에서 CW(Contention Window)에 따른 성능과 에너지 소비량을 분석한다. 기존 연구에서는 802.15.4 표준안의 성능과 에너지 소비량을 분석하고, CW나 BE(Backoff Exponent)와 같은 변수를 변화시켜 시뮬레이션만으로 성능과 에너지 소비량을 비교하여 분석하였으나, 본 논문은 CW에 따른 성능과 에너지 소비량을 마코프 체인(Markov Chain)을 이용하여 수학적으로 분석을 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.1042-1044
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• 2007

IEEE 802.15.4 표준을 기반으로 하는 무선 액세스 기술은 진화된 컴퓨팅 시스템을 구축하는 데 있어 광범위하게 사용될 수 있을 것이다. 이러한 기술의 활용은 보안성과 공정성이 보장되어야 하지만, 무선 환경에서 악의적인 디바이스는 불공정한 방법을 사용하여 채널 대역폭을 차지할 수 있다. 본 논문에서는 이러한 공격에 대응할 수 있도록 코디네이터의 결정에 의해 정상적인 디바이스가 채널에 우선적으로 액세스 할 수 있는 메커니즘을 제안하고, 이를 위해 기존의 IEEE 802.15.4 표준을 활용할 수 있는 방안을 제시한다. 시뮬레이션 결과는 본 논문에서 제안하는 메커니즘이 MAC 레이어에서의 공격을 효과적으로 방지할 수 있음을 보여준다.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.11
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• pp.32-40
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• 2016

IEEE 802.15.4 is the one of the protocols for radio communication in a personal area network. Because of low cost and low power communication for IoT communication, it requires the highest optimization level in the implementation. Recently, the studies of location aware algorithm based on IEEE802.15.4 standard has been achieved. Location estimation is performed basically in equal consideration of reference node information and blind node information. However, an error is not calculated in this algorithm despite the fact that the coordinates of the estimated location of the blind node include an error. In this paper, we enhanced a conventual maximum likelihood estimation using weighted coefficient and implement the hardwired location aware engine for small code size and low power consumption. On the field test using test-beds, the suggested hardware based location awareness method results better accuracy by 10 percents and reduces both calculation and memory access by 30 percents, which improves the systems power consumption.

• Journal of Advanced Navigation Technology
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• v.13 no.2
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• pp.238-243
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• 2009

Now, the production process systems are largely based on automatic system using the wired network. The production process systems using wired network has disadvantage that it is expensive when the installed and replaced equipment. The each equipment happens to repair cost for control and management in production processes. And the replaced equipment has also the additional expense and breaks production process. These problems are solved through wireless communication between the industrial equipments. So, we propose wireless production process system based on IEEE 802.15.4 technology. It solves a complicated space and stops by replaced equipment in the factory. Then we simulated and analyzed IEEE 802.15.4 for Industrial Equipment based on Wireless Network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.247-256
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• 2013

According to the complete standard document for PHY/MAC layer of visible light communication through the IEEE 802.15.7 WG on Sept. 2011, visible light communication lays a good foundation for developing a variety of application services. Thus, visible light communication moves to the advanced research period for developing application services, but most of applications are limited only to PtP service model. However, PtMP communication environment for VLC is required to accommodate more various applications. In this paper, we analyze an effect of key parameters on network performance in the star topology based visible personal area network system. We implement a simulator with considering attributes of PHY and MAC layer which are defined by IEEE 802.15.7 standard documents, and analyze the VLC performance.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.5
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• pp.19-27
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• 2010

In this paper, we propose a scheme for real-time data retransmission in LR-WPAN to support the required QoS even in the severe channel error environments. In IEEE 802.15.4a, as the user data rate is supported up to 850Kbps, the real-time streaming data can be transferred more easily. In this research, we study the beacon-enabled mode in IEEE 802.15.4 LR-WPAN standard. In the proposed scheme, special slots are dynamical1y assigned for retransmission of the packet that fails during a real-time data service, and in the severe channel error environments a time diversity is acquired. Analytical results show that the proposed scheme is more robust and achieves a much higher throughput than the previous protocol in LR-WPAN.

• Journal of Internet Computing and Services
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• v.10 no.4
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• pp.213-222
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• 2009

IEEE 802.15.3 HR-WPAN is designed to enable wireless connectivity of high-speed, low-power, low-cost multimedia-capable portable consumer electronic devices. For quality of service, the standard specifies the use of TDMA (Time Division Multiple Access). However, during low contention TDMA gives much lower channel utilization and higher delays than CSMA (Carrier Sensing Multiple Access) because in TDMA, a node can transmit only during its scheduled time slots whereas in CSMA, nodes can transmit at any time as long as there is no contention. By mixing CSMA and TDMA, Hybrid MAC becomes more robust to timing failures, time-varying channel conditions, slot assignment failures and topology changes than a stand-alone TDMA.