• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권1호
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• pp.26-51
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• 2009

In this paper, we propose an empirical framework for modeling and emulating interference in multi-hop wireless ad-hoc networks. Wireless interference causes wide variation in the frame delivery rate at a link, and thus we cannot represent the state of the link with only two states, connected state and disconnected state, as in wired networks. We first investigate wireless interference in detail, in order to accurately calibrate the interference and identify its underlying attributes, and then we simulate the diverse occurrences and effects of interference, after incorporating the scheme into a simulation tool. Based on these observations, we devise a modeling and simulation framework with several control parameters, and perform an extensive set of simulation studies. The simulation results indicate that the proposed framework enables us to examine various attributes of wireless interferences and their effects on wireless network protocols and systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권8호
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• pp.2691-2707
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• 2014

Medium access control is critical in wireless networks for efficient spectrum utilization. In this paper, we introduce a novel collision resolution method based on the technique of known interference cancellation, and propose a new MAC protocol named as CR-MAC, in which AP tries to decode all the collided data packets by combining partial retransmissions and known interference cancellation. As the collided transmissions are fully utilized, less retransmission is required, especially in a crowded network. The NS-2simulation and MATLAB numerical results show that, under various network settings, CR-MAC performs much better than the IEEE 802.11 DCF in terms of the aggregation throughput and the expected packet delay.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.681-685
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• 2004

Design of efficient Medium Access Control (MAC) protocols with both high throughput performances is a major focus in distributed contention-based MAC protocol research. In this paper, we propose an efficient contention-based MAC protocol for wireless Local Area Networks, namely, the Developed Collision Resolution (DCR) algorithm. This algorithm is developed based on the following innovative ideas: to speed up the collision resolution, we actively redistribute the backoff timers for all active nodes; to reduce the average number of idle slots, we use smaller contention window sizes for nodes with successful packet transmissions and reduce the backoff timers exponentially fast when a fixed number of consecutive idle slots are detected. We show that the proposed DCR algorithm provides high throughput performance and low latency in wireless LANs.

• 대한임베디드공학회논문지
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• 제8권6호
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• pp.329-337
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• 2013

In multihop routed ad hoc networks, the conventional store-and-forward delivery has been used. However, we may ask a question: "Is the store-and-forward delivery still the best?" This paper presents a pipeline-through MAC (PT-MAC) protocol for ad hoc networks, in which nodes have two 3-channel interfaces in order to use limited radio resources efficiently and improve network performance. The proposed protocol reduces end-to-end delay significantly in multihop routed transmission by exploiting a novel pipeline-through technique rather than using the conventional store-and-forward. This results in improved network performance without increasing control overhead. Our extensive performance study shows that the proposed PT-MAC shows 20-40 percent shorter end-to-end delay and 25-55 percent better goodput compared to the IEEE 802.11 DCF with two 3-channel interfaces.

• 산업기술연구
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• 제28권A호
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• pp.113-117
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• 2008

Wireless carrier sense multiple access (CSMA) systems are widely used but show extremely different transmission efficiency according to the operation environment. Simulation or prototype deployment is needed to see the transmission efficiency of a wireless CSMA system with the partial packet retransmission scheme. The lower bound for the transmission efficiency of such a system is found mathematically in this work. This shows how much the partial packet retransmission scheme improves the transmission efficiency quantitatively. It also shows that the maximum throughput is obtained at higher offered load compared to the conventional CSMA system without the partial packet transmission. The result of this work can be applied to IEEE 802.11 networks or wireless mesh networks.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.209-211
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• 2005

This paper proposes a adaptive medium-access control(MAC) protocol designed for low-power wireless multi-hop sensor networks which is used for connecting physical world and cyber computing space. Wireless multi-hop sensor networks use battery-operated computing and sensing device. We expect sensor networks to be deployed in an ad hoc fashion, with nodes remaining inactive for long time, but becoming suddenly active when specific event is detected. These characteristics of multi-hop sensor networks and applications motivate a MAC that is different from traditional wireless MACs about power conservation scheme, such as IEEE 802.11. Proposed MAC uses a few techniques to reduce energy consumption. Result show that proposed MAC obtains more energy savings.

• 제어로봇시스템학회논문지
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• 제14권8호
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• pp.760-766
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• 2008

This paper proposes an efficient location technique to find an indoor location under the IEEE 802.11 wireless local area networks. The proposed method is based on the range measurements obtained from a simple radio frequency propagation model. Thus, unlike the radio frequency fingerprint correlation method, it does not suffer from the computational burden during the real-time location service period and can quickly reply the location requests of many users at the same time. To increase the location accuracy in spite of the frequent non-line-of-sight error occurrences, the proposed method calibrates the distortion of the non-line-of-sight error by a simple measurement surveying procedure that does not require the surveyor's manual interaction. Experimental results show the capability of the proposed method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.1131-1132
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• 2008

In this paper, we developed UHF RFID R/W system using AT91SAM7S256(ARM chip), UHF RFID R/W module (WJ7090) and wireless LAN(IEEE 802.11.a/b). And we developed a transmission/receiving packet which is send to UHF R/W module in AT91SAM7S256. In order to show the usefulness of UHF RFID R/W system, we executed a performance test. The developed UHF RFID R/W system shows better performance for reading of RFID tag and data transmission through wireless LAN.

• 한국철도학회논문집
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• 제9권3호
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• pp.257-263
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• 2006

This paper presents an optimization approach to the configuration of train radio communication network for CBTC. The target specifications of CBTC communication systems are derived from technical requirements for CBTC. The proposed communication system has a ring-topology backbone communication network between stations and a radio network based on IEEE 802.11b wireless tan between trains and wayside devices. The proposed method has been applied to the standardization of the signalling system of urban transits.

• 전자공학회논문지S
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• 제34S권9호
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• pp.1-12
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• 1997

The performance of Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol adopted as a draft standard of IEEE 802.11 wireless LAN, is analyzed by using mathematical method based on renewal theory. We introdude three kinds of CSMA/CA protocols basic, stop-and-wait and 4-Way handshake CSMA/CA with their mathematical analysis. First, a network of finite population is considered and then expand to infinite population. We model the CSMA/CA protocol as a hybrid protocol of 1-persistent CSMA and p-persistent CSMA protocol, and verify analaytical results by computer simulation. We have found that 4-Way Handshake CAMA/CA shows better performance than those of other two types of CSMA/CA in case of high traffic load.