• Journal of Korean Institute of Industrial Engineers
• /
• 제33권2호
• /
• pp.237-245
• /
• 2007

In this paper, a modified PCF (Point Coordination Function) MAC (Medium Access Control) Protocol is proposed to support the multiple direct link communication between STAs (STAtions) in infrastructure mode IEEE 802.11 wireless LANs. By the proposed MAC protocol, the direct link communication between STAs, which are located within the communication range of each other, is allowed without the use of AP (Access Point) as a relay. Moreover, when multiple direct data communication between STAs can be simultaneously performed with a sufficiently small interference, multiple simultaneous direct link communication is allowed for the efficient use of radio bandwidth. AP polls STAs to grant the transmission opportunities using the direct link communication by transmitting the polling frames to STAs. An efficient polling method for granting the transmission opportunities to STAs is proposed to reduce the number of the polling frame transmissions and enhance the PCF MAC performance.

• Journal of Digital Contents Society
• /
• 제4권2호
• /
• pp.203-210
• /
• 2003

In this paper we proposed a new MAC protocol to improve QoS(Quality of Service) for real-time traffic in wireless Ad Hoc networks. NMAC protocol have a contention period reservation scheme and a priority control scheme to provide fairness of nodes and QoS. Through simulation, the NMAC protocol compared with existing CSMA MAC protocols shows improvement in performance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 한국해양정보통신학회 2004년도 춘계종합학술대회
• /
• pp.674-677
• /
• 2004

최근 대부분의 전송기술(LAN 뿐만 아니라 MAN과 WAN까지)이 이더넷으로 통일되는 경향에 힘입어, 예전에 비하여 이더넷은 최근에 대단한 주목을 받게 되었다. 그러나 그동안 ATM 등의 전송기술에 의해 관심밖에 있던 이더넷이기 때문에, 국내에서 축적된 기술도 미약하다. 그리고, 이더넷이라는 기술은 단순한 디지털 로직이 아닌 디지털 / 아날로그 모뎀기술과 광 전송기술, 소프트웨어기술들이 결합된 고도의 전송기술이기 때문이다. 10Gbps 이더넷 표준이 2002년에 발표되면서 10Gbps 이더넷에 대해 많은 연구가 지속되고 있다. 10Gbps 이더넷의 특징은 이더넷 고유의 CSMA/CD 방식을 지원하지 않고, 점대점 전이중 방식만을 지원하고, 기존의 프레임구조는 계속 유지하였다. 본 연구에서는 10Gbps 이더넷 Data Link 계층의 MAC(Media Access Control) 코어를 C언어를 이용하여 성능평가를 실시하여 활용 가능한 응용분야와 내부 FIFO와 파라미터 초기 값을 도출하였다. 성능평가 결과 MAC 모듈은 짧은 패킷이 유입되었을 때 95%까지, 일반 패킷이 유입되었을 때 97%까지 패킷 손실이 발생하지 않음을 확인하였다.

• Journal of Korea Multimedia Society
• /
• 제17권5호
• /
• pp.631-639
• /
• 2014

Recently, research on Media Access Control (MAC) techniques for underwater acoustic communication has been conducted actively. For successful acoustic communication in underwater conditions, development of environmentally adaptive MAC techniques, which is taking narrow bandwidth, distance, depth, noise level, salinity, multipath and etc into account, is an especially important work. In this paper, knowledge based system is introduced not only to obtain adaptive and optimal communication parameters but also increase network efficiency and availability by requesting change of MAC techniques based on decisions from knowledge-based system Smart Decision Block (SDB). Computer simulations were also conducted to verify the performance of the proposed system in underwater conditions.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제29권12A호
• /
• pp.1367-1374
• /
• 2004

Efforts for standardization of medium access control (MAC) protocol in IEEE802.11e have been made to support quality of service (QoS) in IEEE802.11 MAC protocol. Enhanced distributed coordination function (EDCF) of 802.11e MAC protocol is modified to support QoS for packets that have differentiated priority. However, EDCF still has e problem of throughput optimization and priority support. Therefore, we have proposed a scheme called adaptive EDCF for both supporting priority of packets and throughput optimization. We have derived the relation between the number of nodes and contention window size for throughput optimization. Based on the analytic results, we have evaluated the performance of the proposed scheme using OPNET simulations. The simulation results show that using the proposed scheme can Improve the overall throughput regardless of the number of nodes and the decrement of the throughput with increasing the number of nodes can be alleviated. Additionally, we have shown that the adaptive EDCF can support priority of packets more effectively than existing EDCF.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• 제20권2호
• /
• pp.75-80
• /
• 2020

There are so many low power MAC protocols for wireless sensor network. IEEE802.15.4 among them has disadvantage of a large power consumption for synchronization. To save power consumption it use the superframe operation alternating sleep mode and awake mode. But latency is longer result from superframe operation. B-MAC can have shorter latency according to check interval. But transmitter consumes more power because of long preamble. And receiver is suffering from overhearing. In this paper, we use the adaptive check interval scheme[1] of B-MAC for enhancing the power consumption. Its maximum throughput and minimum delay is evaluated by comparing the proposed scheme with a typical single channel IEEE802.15.4.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• 제19권10호
• /
• pp.2465-2472
• /
• 2015

Wireless Medium Access Control (MAC) and routing technologies are the basic building blocks making it possible the Internet of Things (IoT). These technologies have been the focus of substantial research in the last decade. Nevertheless, as new networking standards for IoT are being proposed and different solutions are patched together, evaluating the performance of the network becomes unclear. In this paper, a new overview of MAC and routing protocols for IoT and new interactions are given. The IEEE 802.15.4 MAC and Routing Protocol for Low-power Lossy Network (RPL) routing protocols are taken as reference to exemplify and illustrate the discussion. Experimental results show that contention-based access MACs may hurt the routing, unless these two are carefully designed together.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제34권11B호
• /
• pp.1200-1206
• /
• 2009

In this paper, we propose an energy-efficient MAC(Medium Access Control) protocol for processing context information in ubiquitous sensor network environments. CASMAC(Context Aware Sensor MAC) use context information for energy-efficient operation and its operation principle is as follows. First, we make scenarios with possible prediction for CASMAC. And then we save setted context information in server. When event occur at specific sensor node, and then it send three times sample data to server. According to context information, server process sample data. If server process sample data with event, it receive continuous data from event occur node by a transmission request signal. And then server send data transmission stop signal to event occur node when it do not need to data. If server process sample data with no event, it have not reply. Through we make energy consumption tables and an energy consumption model, we simulate analysis of CASMAC performance. In a result, we gains about 5.7 percents energy reduction compared to SMAC.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제30권1A호
• /
• pp.62-69
• /
• 2005

Efforts for standardization of medium access control (MAC) protocol in IEEE802.11e have been made to support quality of service (QoS) in IEEE802.11e MAC protocol. Enhanced disoibuted coordination function (EDCF) of 802.11e MAC protocol is modified to support QoS for packets that have differentiated priority. However, EDCF still has the problem of throughput optimization and priority support. Therefore, we have proposed a scheme called adaptive EDCF for both supporting priority of packets and throughput optimization. We have derived the relation between the number of nodes and contention window size for throughput optimization. Based on the analytic results, we have evaluated the performance of the proposed scheme using OPNET simulations. The simulation results show that using the proposed scheme can improve the overall throughput regardless of the number of nodes and the decrement of the throughput with increasing the number of nodes can be alleviated. Additionally, we have shown that the adaptive EDCF can support priority of packets more effectively than existing EDCF.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• 제28권6호
• /
• pp.1343-1354
• /
• 2018

OAuth 2.0 bearer token and JWT(JSON web token), current standard technologies for authentication and authorization, use the approach of sending fixed token repeatedly to server for authentication that they are subject to eavesdropping attack, thus they should be used in secure communication environment such as HTTPS. In OAuth 2.0 MAC token which was devised as an authentication scheme that can be used in non-secure communication environment, server issues shared secret key to authenticated client and the client uses it to compute MAC to prove the authenticity of request, but in this case server has to store and use the shared secret key to verify user's request. Therefore, it's hard to provide stateless authentication service. In this paper we present a randomized token authentication scheme which can provide stateless MAC token authentication without storing shared secret key in server side. To remove the use of HTTPS, we utilize secure communication using server certificate and simple signature-based login using client certificate together with the proposed randomized token authentication to achieve the fully stateless authentication service and we provide an implementation example.