• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.95-105
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• 2010

IEEE 802.15.4 is the one of the protocols for radio communication in a personal area network. Since it aims to provide low cost and low power communication for ubiquitous communication, it requires high level of optimization in implementation. Recently, there have been many studies on the performance evaluation of IEEE 802.15.4 MAC protocol. According to the results of the studies, it is tendency that the transceiver is implemented to SoC type. On the implementation, the specific functions of MAC like CSMA-CA and MAC frame handling is designed to hardwired functions. In this paper, we implemented the protocol with hardwired low MAC (HL-MAC) and its state machine for the optimization from the physical layer and MAC layer. it has the characteristics of the small code size and the enhanced power consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.463-468
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• 2009

In VANET(Vheicle Ad hoc Network), the researches based on the wireless LAN are conducting and the method based on 802.11a is being adapted in IEEE 802.11p WAVE(Wireless Access in Vehicular Environments). However, wireless LAN which uses a single channel in a competition can cause transmission delays because of a frequent collision and a use of CSMA/CA to avoid competition in VANET requiring a fast access. In this paper, we designed CMMP (Clustering based Multi-channel MAC protocol) adequate to VANET and then confirmed the appropriate channel conditions in a V2V communication on the basis of this protocol. The simulation results showed that a packet collision and a transmission delay by the use of an existing single channel based on the contention decreased more than 60% by CMMP.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.371-380
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• 2020

Video is principal information that facilitates commander's immediate command decision. Due to fading characteristics of radio link, however, it is difficult to stably transmit video in a multi-hop wireless environment. In this paper, we propose a MANET structure composed of a link adaptive routing protocol and a TDMA MAC protocol to stably transmit video traffic in a ultra-narrowband video streaming network. The routing protocol can adapt to link state change and select a stable route. The TDMA protocol enables collision-free video transmission to a destination using multi-hop dynamic resource allocation. As a result of simulation, the proposed MANET structure shows better video transmission performance than proposed MANET structure without link quality adaption, AODV with CSMA/CA, and OLSR with CSMA/CA structures.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1877-1884
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• 2014

Because of the limited power resource, we need a reliable low-power media access control technique suitable for unmaned remote sensor operation condition for the unmanned sensor processor to perform the task in the remote wireless network situation. Therefore CSMA/CA and X-MAC is generally considered to effectively transmit the signal in the low-power wireless network. In this paper, we propose the more efficient low-power LP-MAC Technique which consumes the minimum power and transmits the data faster in condition that the mobile nodes' joining to and leaving from the network which consists of the fixed nodes is fluid. The fixed nodes operate in an asynchronous mode to perform the network self-configuration and transmit data faster to the mobile node which is frequently join and leave the network. When the mobile node leaves the network, the network's operation mode will be synchronous mode to achieve the minimum power consumption, thus the minimum power operation becomes possible.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.4
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• pp.453-461
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• 2019

In this paper, we focus on the study of multi-node rendezvous on one common channel among multiple channels before transmitting in CRAHNs (Cognitive Radio Ad-hoc Networks) for the efficient use of inefficient frequency resources. Most existing researches have dealt with the channel rendezvous between two nodes. But, it can be time-consuming to apply them to three or more nodes. In addition, it cab be impossible to communicate with each other. Therefore, in this paper, we propose a Multi-Node Sequence (MNSEQ), which allows three or more nodes to rendezvous on a single common channel in a short period of time. And, CSMA/CA was applied for data exchange after rendezvous. By performance evaluation through very extensive simulations, we have demonstrated that the proposed MNSEQ outperforms the existing scheme in terms of communication completion time and transmission efficiency.

• Journal of Biomedical Engineering Research
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• v.19 no.1
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• pp.19-24
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• 1998

The main goal of this paper is to propose and to test a radio protocol based CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) for the purpose of enhancing the existing medical information system. The feature of the new medical information system, Medical Application Radio System(MARS), which operating in real time is the transmission of medical information in bi-direction between the hospital control office and patients mobile stations. MARS monitors patients linked to the network by radio and provides quick alarm, flexible documentation capabilities, asnd fast treatment for the analysis of collected medical data. The existing medical information system, radio telemetry system which transfers the message of patients to the CAP(Central Access Point) unit in one way at the speed of 9.6Kbps and operates a channel frequency bandwidth. To verify the Performance of the proposed system, we have performed the numerical analysis and have implemented a test system which consists of the 2.4Ghz radio transceiver and personal computer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.391-398
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• 2011

In this paper, we propose a MAC protocol for visible light wireless LAN using LED light. The proposed MAC protocol has a function of automatic direction optimization for LED transceiver. There is periodical time slot for broadcasting and registration in the proposed MAC protocol. We used polling method for data transfer in the protocol since visible light is hard to detect carrier and collision by other mobile stations; thus we cannot use CSMA/CD method in visible light LAN. We also amended the MAC frame of IEEE 802.11 to propose a revised version for visible light wireless LAN using LED light. We investigate the performance of the proposed MAC protocol. When the bit rate of physical layer is 100 Mb/s, the net data throughput using the proposed MAC protocol is estimated to 94.386 Mb/s.

• The KIPS Transactions:PartC
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• v.16C no.3
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• pp.373-382
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• 2009

we present more efficient method of a medium access for real-time ubiquitous sensor networks. Proposed MAC protocol is like the randomized CSMA/CA protocol, but unlike previous legacy protocols, it does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports from sensor nodes, we carefully decide to select a fixed-size contention window with non-uniform probability distribution of transmitting in each slot. We show that the proposed method can offer up to several times latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using a widely-used network simulation package, NS-2. We finally show that proposed MAC scheme comes close to meet bounds on the best latency being achieved by a decentralized CSMA-based MAC protocol for real-time ubiquitous sensor networks which is sensitive to latency.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.412-414
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• 2005

무선 랜 표준인 IEEE 802.11은 원래 best effort service를 위해 탄생된 기술이기 때문에 QoS(Quality of Service)에 대한 연구가 부족했다. 무선 랜에서는 기존 유선 랜보다 한정된 자원과 희박한 bandwidth, 다양한 노드들의 채널 공유로 인해 QoS를 보장하기가 어렵다. 이를 보완하기 위한 연구가 IEEE 802.11e 워킹그룹에서 진행되고 있다. 본 논문에서는 충돌방지를 위한 CSMA/CA 알고리즘의 back-off값 설정을 매개변수를 두어 idle 시간을 조정함으로써 QoS를 보장하는 알고리즘을 제안한다. 특히, QoS가 요구하는 패킷전달 간격 임계값(threshold)에 따른 매개변수를 조절하여 contention window 크기를 달리 조정함으로써 QoS를 요구하는 노드들의 수에 상관없이 균일한 서비스 성능을 유지하도록 한다. 이 때, 매개변수 값의 선택은 QoS를 제공하는 노드들의 서비스 성능 뿐 아니라 best effort service만을 제공해도 되는 일반 노드들의 서비스 성능도 함께 고려할 수 있도록 하였다.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.3
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• pp.205-212
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• 2017

This paper focuses on worst-case delay analysis of the time-triggered IEEE 802.15.4 protocol to satisfy the industrial quality-of-service (QoS) performance. The IEEE 802.15.4 protocol is considered to be unsuitable for industrial networks because its medium access control method is contention-based CSMA/CA, which exhibits unstable performance with an unbounded delay distribution under heavy traffic. To avoid these limitations, this paper presents a time-triggered version of the nonbeacon-enabled network of IEEE 802.15.4 that relies on a time division multiplexing access (TDMA) method implemented in the application layer without any modification of specification. The timing analysis of this time-triggered IEEE 802.15.4 was executed, and the worst-case transmission delay was calculated. Based on this analysis, the time-triggered IEEE 802.15.4 is a promising alternative for wireless industrial networking.