• Journal of KIISE:Information Networking
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• v.34 no.3
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• pp.175-185
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• 2007

In IEEE 802.15.4 (Low-Rate Wireless Personal Area Network) specification, a successful reception and validation of a data or MAC command frame can be confirmed with an acknowledgment. However, the specification does not support security for acknowledgment frame; the lack of a MAC covering acknowledgments allows an adversary to forge an acknowledgment for any frame. This paper proposes an identity authentication mechanism at the link layer for acknowledgment frame in IEEE 802.15.4 network. With the proposed mechanism there is only three bits for authentication, which can greatly reduce overhead of device. The encrypted bit stream for identity authentication will be transmitted to device by coordinator within association process. Statistical method and simulation results prove that our mechanism is successful in handling MAC layer attack.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.973-976
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• 2005

In IEEE 802.15.4 (Low-Rate Wireless Personal Area Network) specification, a successful reception and validation of a data or MAC command frame can be confirmed with an acknowledgment. However, the specification does not support security for acknowledgment frame; the lack of a MAC covering acknowledgments allows an adversary to forge an acknowledgment for any frame. This paper proposes an identity authentication mechanism at the link layer for acknowledgment frame in IEEE 802.15.4 network. With the proposed mechanism there is only three bits for authentication, which can greatly reduce overhead. The encrypted bit stream for identity authentication will be transmitted to device by coordinator within association process. Statistical method indicates that our mechanism is successful in handling MAC layer attack.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.319-321
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• 2006

본 논문에서는 블록 FEC(Forward Error Correction) 알고리즘을 적용한 IEEE 802.11e MAC(Medium Access Control)의 블록전송모드(Block Transfer Mode)의 성능을 분석한다. 성능 향상을 위해서 IEEE 802.11e MAC은 TXOP(Transmission Opportunity)시간 동안 특정 스테이션(station)에게 독점적인 전송 기회를 부여하며, 이 기간동안 하나의 블록 즉 연속적으로 여러 개의 데이터 프레임(frame)을 전송한다. 수신자는 블록내의 각 프레임에 수신 여부를 블록 ack (block Acknowledgment)방식, 즉 하나의 ack 패킷이 모든 수신 프레임의 일련번호를 모아 알려 준다. 그러나 오류가 빈번한 무선 채널 환경에서는 블록 ack 방식을 사용하더라도 빈번한 재전송으로 인해 채널의 성능이 현저히 감소한다. 이러한 문제를 해결하기 위해 심볼 단위로 오류를 복원하는 블록 FEC 알고리즘을 적용할 수 있는데, 본 논문에서는 802.11e에서 FEC 알고리즘을 적응하는 두 가지 방식의 성능을 해석적으로 분석한다. 즉 두 가지 방식은 프레임 당 블록 FEC를 적용하는 방법과 전체 블록 내의 프레임을 하나의 데이터로 간주하여 FEC를 적용하는 방식이다. 본 논문에서는 이 들 두 가지 방식의 채널 성능 향상 정도와 블록 ack만을 사용한 경우의 성능을 수식적으로 계산한다. 실험에 의하면 BER이 $10^{-4}$인 채널 환경에서 블록 FEC를 적용한 방식이 블록 ack를 사용한 방식에 비해 약 1.5%의 성능향상을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.720-740
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• 2011

Wi-Fi-enabled portable devices have recently been introduced into the consumer electronics market. These devices download or upload content, from or to a host machine, such as a personal computer, a laptop, a home gateway, or a media server. This paper investigates the fairness among multiple Wi-Fi-enabled portable devices in a home network when they are simultaneously communicated with the host machine. First, we present that, a simple IEEE 802.11-based home network suffers from unfairness, and the fairness is exaggerated by the wireless link errors. This unfairness is due to the asymmetric response of the TCP to data-packet loss and to acknowledgment-packet loss, and the wireless link errors that occur in the proximity of any node; the errors affect other wireless devices through the interaction at the interface queue of the home gateway. We propose a QoS-provisioning framework in order to achieve per-device fairness and service differentiation. For this purpose, we introduce the medium access price, which denotes an aggregate value of network-wide traffic load, per-device link usage, and per-device link error rate. We implemented the proposed framework in the ns-2 simulator, and carried out a simulation study to evaluate its performance with respect to fairness, service differentiation, loss and delay. The simulation results indicate that the proposed method enforces the per-device fairness, regardless of the number of devices present and regardless of the level of wireless link errors; furthermore it achieves high link utilization with only a small amount of frame losses.