• Journal of Digital Contents Society
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• v.4 no.2
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• pp.203-210
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• 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 Korea Information Processing Society Conference
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• 2012.11a
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• pp.15-16
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• 2012

본 논문에서는 우선순위 기반의 RTS/CTS 통신 기법을 적용하여 생체모방형 ROV 를 제어하기 위한 수중 MAC 프로토콜을 제안하였다. MANET 기반의 하천 수질 환경 감시 시스템이 효율적으로 운용되기 위한 수중 MAC 프로토콜이 지원됨으로써 이동성이 강조되는 생체모방형 ROV 제어를 위한 실시간성을 보장할 수 있다.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.168-171
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• 2003

IEEE 802.16 Wireless MAN standard specifies the air interface of fixed point-to-multipoint broadband wireless access systems providing multiple services. Among the service classes supported by the wireless MAN, the best effort service class is ranked on the lowest position in priority and is assisted by a MAC scheme based on reservation ALOHL Such MAC scheme must include a number of components, while many of them are not specified in the standard. In this paper, we thus reveal main components of a MAC scheme supporting the best effort service and present candidate schemes implementing such components. Combining schemes for implementing components, we then construct distinctive MAC schemes supporting best effort service. In designing a MAC scheme, the delay performance induced by the scheme should be considered since scarce resource may be available for the best effort service after the preemptive resource occupation by other service classes. In this paper, we focus on the delay fairness among the subscriber stations using the best effort service. For evaluating a MAC scheme in delay fairness, we present two definitions of delay fairness and provide a criterion for optimal MAC scheme according to each definition of delay fairness. Using a simulation method we investigate the mean delay performance exhibited by each MAC scheme arid find an optimal scheme in delay fairness. From numerical examples, we observe that SR/ED/PG＋P scheme has strong delay fairness compared with MR/ED/PG＋P and SR/ED/PG＋D schemes according to a definition of delay fairness. However, other schemes are rather shown to have better delay fairness when the other definition is adopted.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2811-2817
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• 2010

In this paper we propose the QAC-MAC that supports Quality of Service(QoS) and saves energy resources of the sensor node, and hence prolonging the lifetime of the sensor network with multiple sink nodes. Generally, the nodes nearest to the sink node often experience heavy congestion since all data is forwarded toward the sink through those nodes. So this critically effects on the delay-constraint data traffics. QAC-MAC uses a hybrid mechanism that adapts scheduled scheme for medium access and scheduling and unscheduled scheme based on TDMA for no data collision transmission. Generally speaking, characteristics of the real-time traffic with higher priority tends to be bursty and has same destination. QAC-MAC adapts cross-layer concept to rearrange the data transmission order in each sensor node's queue, saves energy consumption by allowing few nodes in data transmission, and prolongs the network lifetime.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1A
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• pp.132-141
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• 2000

In this paper, we proposed the MAC protocol of APON supporting multi-class traffic such as CBBUVBR, ABR, UBR, to guarantee the required QoS of each service. For this, we analyze the performance of variousrequest mechanisms and employee the different request mechanism for each traffic classes. Upstream anddownstream frame structures to minimize transmission overhead are proposed based on our request mechanism.The proposed MAC protocol applies the different priority to permit distribution process. CBBWBR traffic, withthe stringent requirements on CDV or delay, is allocated prior to any other class. ABR traffic, which hasnon-strict CDV or delay criteria, uses flexibly the available bandwidth but ensures a minimum cell rate (MCR).UBR traffic is allocated with lowest priority for the remaining capacity. The performance of proposed protocol isevaluated in terms of transfer delay and 1-point CDV with various offered load. The result of simulation showsthat the proposed protocol guarantees the required QoS of the corresponding category, while making use of theavailable resources in both an efficient and dynamical way.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.20-21
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• 2008

In the IEEE 802.16 Wireless MAN standard, the best effort service class is ranked on the lowest position in priority so that only scarce resource may be available for it. Also, the best effort service is usually assisted by a MAC scheme based on reservation ALOHA without explicit acknowledgement. However, the standard only specifies the skeleton of the MAC scheme. In this paper, we propose some rules to specify the indefinite part of the MAC scheme as well as to improve the throughput and delay performance of the MAC scheme. As generic rules for demanding and granting resource, we first propose non-gated exhaustive, gated exhaustive, non-gated limited, and gated limited demand rules, and deficient and full grant rules. Secondly, we propose grant regulation rules, identified as replacement and lifetime rules, to avoid excessive grant incurred by not giving acknowledgement. Noting the residual resource is inflated by adopting a grant regulation rule, we finally propose a rule for investing the residual resource to a subscriber station. Simulation results confirm that a combination of proposed rules improves the performance of the MAC scheme.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.581-585
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• 2006

무선랜 환경에서의 효율적인 비디오 스트리밍을 하기위해서는 불안정한 네트워크 대역폭과 패킷지연, 패킷손실 등의 문제가 해결 되어야 한다. 본 논문에서는 서비스 품질의 보장을 위해 기존의 Best-effort에 기반한 IEEE 802.11 MAC 프로토콜을 향상시킨 IEEE 802.11e MAC 프로토콜을 이용하여 Cross-layer 기반의 프레임 우선순위화 기법을 제안 하였다. 멀티미디어 트래픽의 프레임 중요도에 따라 다르게 부여한 Priority를 이용해 IEEE 802.11e MAC 프로토콜의 차별화된 데이터 전송을 하였으며, 네트워크 상태 모니터링을 통해 중요도가 낮은 프레임을 우선적으로 폐기하는 적응적 전송율 조절 기법을 제안하였다. 실험 결과는 제안하는 Cross-layer기반의 프레임 우선순위화 기법이 멀티미디어 스트리밍의 종단간 QoS를 향상 시킬 수 있음을 보여준다.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.679-686
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• 2005

Because EPON access network shares a medium and aggregates the traffic from EPON subscribers, scheduling media access control on EPON bandwidth allocation is very important. Furthermore DBA mechanism of EPON based on TDMA is out of specification and up to implementation. This paper deals with a DBA method to guarantee the QoS of the delay sensitive traffic on the base of best-effort service and delay priority queue management. The proposed method performs virtual scheduling algorithm for the integrated traffic. It uses the same MAC messages and tries to guarantee the QoS of higher priority traffic first with a simple DBA architecture. We evaluate the algorithm for traffic delay according to polling interval and traffic load of upstream and downstream. The results show that the proposed method can guarantee the QoS of the delay sensitive traffic with priority of the service classes.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.114-121
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• 1998

This paper proposed a collision avoidance scheme to improve the network performance and priority control scheme to support real-time ATM applications in CIF(Cells in Frames), which carries ATM cells over existing Ethernet interfaces. The proposed scheme has optimized for the two nodes Ethernet, that is a typical CIF network, and doesn't require any hardware modification of existing Ethernet interface card. The collision avoidance scheme gives fair access opprtunities with minimized contention to the nodes by assigning different inter-frame gap to each element of CIF network. The priority control scheme guarantees preemptive transmission of real-time frames to the medium by exchanging queuing status information between two nodes. Therefore in this paper it is shown that CIF network which has both the collision avoidance scheme of MAC layer and the priority control scheme of CIF layer has a improved network performance and supports real-time ATM applications efficiently.

• The Transactions of the Korea Information Processing Society
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• v.7 no.9
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• pp.2940-2947
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• 2000

In the wireless ATM networks, a Medium Access Control (MAC) protocol is required to support an integrated mix of multimedia traffic services. The MAC protocol should be designed in a way that the limited wireless bandwidth can be efficiently utilized maximizing the Quality of Service (QoS) guarantees for various traffic service classes. In this paper, a Dynamic Resource Allocation-based MAC protocol, which satisfies QoS of each traffic service class in the wireless ATM environment, is proposed. The proposed MAC protocol adopts the dynamic channel allocation schemes for a mix of different traffic service classes. The suggested MAC protocol is designed to provide the QoS guarantees for Constant Bit Rate (CBR) or real-time Variable Bit Rate (VBR) traffic through fixed or dynamic reservation. For Available Bit Rate (ABH) traffic, which has the lowest priority among the traffic classes, large improvement in delay by reserving the minimum bandwidth is shown. And for real-time VBR traffic, increase in throughput of transmission is demonstrated because of bandwidth, which is allocated through contention at the initial phase and without contention thereafter.