• 한국인터넷방송통신학회논문지
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• 제11권6호
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• pp.267-273
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• 2011

고속의 대역폭과 원활한 트래픽 관리, 그리고 보안 기능을 갖춘 인터넷 접속 네트워크는 기업의 전략적인 인프라로 그 위상이 강화되고 있다. 이러한 전략적 인터넷 인프라로서의 역할을 수행하기 위해서는 늘어나는 트래픽에 맞추어 네트워크 속도의 향상이 있어야 함과 동시에 내/외부 네트워크로부터의 보안공격에 대비하여 안심하고 자원을 사용할 수 있어야 한다. 본 논문에서는 인터넷 속도의 향상, 능동적 네트워크 보안, 응용 및 사용 목적에 따른 트래픽 분할 관리를 통합적으로 제공할 수 있는 솔루션으로서 종단간 트래픽 관리를 지원하는 네트워크 보안 시스템을 개발한다. 제안된 시스템에서는 초고속 인터넷 접속과 방화벽 기능, VPN, 침입 방지, 콘텐츠 필터링, 트래픽 및 QoS 관리, History Log 기능 등을 통합적으로 일체형 장비에 구현하여 기업이 전략적인 인터넷 인프라를 구축하면서도 통신비용을 절감할 수 있는 통합 네트워크 보안시스템을 제공할 수 있다.

• 한국인터넷방송통신학회논문지
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• 제11권2호
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• pp.197-203
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• 2011

애드 혹 네트워크는 네트워크의 구성 요소를 관리하는 AP가 없는 대신 각각의 노드가 라우팅 알고리즘에 의한 동작으로 노드간에 정보를 전송한다. 이 때 네트워크 내 모든 노드로 정보를 전송하는 브로드캐스팅 과정이 필수적이다. 브로드캐스팅 과정에서는 네트워크를 구성하는 노드에 대한 충분한 정보 없이 모든 노드로 패킷을 전송하므로 동일한 패킷의 중복 수신이 발생하며, 이는 네트워크의 전력 효율을 감소시키는 원인이 된다. 본 논문에서는 전송 효율을 증가시키기 위하여 패킷 수신 횟수에 의한 확률적 브로드캐스트 기법을 제안한다. 각 노드는 과거 패킷 수신 횟수에 근거하여 신뢰성이 보장된 범위 내에서 높은 전송 효율을 갖는 브로드캐스트 확률을 계산하고 이 확률에 따라 각 노드는 브로드캐스트를 수행한다. 본 논문에서는 모의 실험을 통하여 제안 기법의 성능을 검증하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권6호
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• pp.3000-3022
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• 2019

Full-duplex (FD) technologies enable wireless nodes to simultaneously transmit and receive signal using the same frequency-band. The FD modes could improve their physical layer throughputs. However, in the wireless ad hoc networks, the FD communications also produce new interference risks. On the one hand, the interference ranges (IRs) of the nodes are enlarged when they work in the FD mode. On the other hand, for each FD pair, the FD communication may cause the potential hidden terminal problems to appear around the both sides. In this paper, to avoid the interference risks, we first model the IR of each node when it works in the FD mode, and then analyze the conditions to be satisfied among the transmission ranges (TRs), carrier-sensing ranges (CSRs), and IRs of the FD pair. Furthermore, in the media access control (MAC) layer, we propose a specific method and protocol for collision avoidance. Based on the modified Omnet++ simulator, we conduct the simulations to validate and evaluate the proposed FD MAC protocol, showing that it can reduce the collisions effectively. When the hidden terminal problem is serious, compared with the existing typical FD MAC protocol, our protocol can increase the system throughput by 80%~90%.

• 한국통신학회논문지
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• 제28권6B호
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• pp.563-572
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• 2003

차세대 이동 통신망 환경에 Mobile IP 방식을 적용하였을 경우 빈번히 발생하는 핸드오프로 인한 재등록 과정의 오버헤드 증가와 등록 시의 지연으로 인한 패킷 손실 증가 등의 마이크로 이동성(micro-mobility) 문제가 발생할 수 있다. 본 논문에서는 이 문제의 해결을 위해 IP 기반 무선 액세스 망에서 마이크로 이동성을 효율적으로 지원하는 ANMM(Access Network Mobility Management) 방식을 제안한다. ANMM 방식은 액세스 망 내에서 노드가 이동할 때 발생하는 핸드오프 등록 과정을 액세스 망 자체적으로 처리하여 등록 지연과 시그널링 오버헤드를 감소시킨다. 또한 핸드오프 시의 무선 구간에서의 시그널링을 최소화하여 무선 자원의 낭비를 줄일 수 있다.

• 정보보호학회논문지
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• 제17권2호
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• pp.61-72
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• 2007

With the increasing growth of Internet and wireless IP networks, Multimedia systems need to be envisaged as information resources where users can access anywhere and anytime. However, efficient services in these multimedia systems are open and challenging research problem due to user mobility, limited resources in wireless devices and expensive radio bandwidth. To implement multimedia services over heterogeneous network, the IP header compression scheme can be used for saving bandwidth. In this paper, we present an efficient solution for header compression, which is modified form of ECRTP. It shows an architectural framework adopting modified ECRTP when IP tunneling network using GRE over IPSec is implemented. We have conducted simulations in order to analyze the effects of different header compression techniques while delivering real-time services to the wireless access network through secured IP Network. The impacts on performance have been investigated through a series of experiments.

• ETRI Journal
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• 제35권3호
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• pp.406-413
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• 2013

In this paper, an orthogonal frequency division multiple access (OFDMA)-based minimum end-to-end delay (MED) distributed routing scheme for mobile backhaul wireless mesh networks is proposed. The proposed scheme selects routing paths based on OFDMA subcarrier synchronization control, subcarrier availability, and delay. In the proposed scheme, OFDMA is used to transmit frames between mesh routers using type-I hybrid automatic repeat request over multipath Rayleigh fading channels. Compared with other distributed routing algorithms, such as most forward within radius R, farthest neighbor routing, nearest neighbor routing, and nearest with forwarding progress, simulation results show that the proposed MED routing can reduce end-to-end delay and support highly reliable routing using only local information of neighbor nodes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.1976-1996
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• 2011

Cognitive radio (CR) MAC protocol provides access control of unused spectrum resources without causing interference to primary users. To achieve this goal, in this paper a TDMA based cooperative multi-channel cognitive radio MAC (MCR-MAC) protocol is proposed for wireless ad hoc networks to provide reliable protection for primary users by achieving cooperative detection of incumbent system signals around the communication pair. Each CR node maintains transmission opportunity schedules and a list of available channels that is employed in the neighbor discovery period. To avoid possible signal collision between incumbent systems and cognitive radio ad hoc users, we propose a simple but efficient emergency notification message exchanging mechanism between neighbor CR nodes with little overhead. Our simulation results show that the proposed MCR-MAC can greatly reduce interference with primary users and remarkably improve the network throughput.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권2호
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• pp.593-609
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• 2012

We propose a scheme to reduce the overhead associated with channel state information (CSI) feedback required for opportunistic scheduling in wireless access networks. We study the case where CSI is partially overheard by mobiles and thus one can suppress transmitting CSI reports for time varying channels of inferior quality. We model the mechanism of feedback suppression as a Bayesian network, and show that the problem of minimizing the average feedback overhead is NP-hard. To deal with hardness of the problem we identify a class of feedback suppression structures which allow efficient computation of the cost. Leveraging such structures we propose an algorithm which not only captures the essence of seemingly complex overhearing relations among mobiles, but also provides a simple estimate of the cost incurred by a suppression structure. Simulation results are provided to demonstrate the improvements offered by the proposed scheme, e.g., a savings of 63-83% depending on the network size.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.764-784
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• 2017

Energy efficiency is an essential requirement in designing a MAC protocol for wireless sensor networks (WSNs) using battery-operated sensor nodes. We proposed a new receiver-initiated MAC protocol, RIX-MAC, based on the X-MAX protocol with asynchronous duty cycles. In this paper, we analyzed the performance of RIX-MAC protocol in terms of throughput, delay, and energy consumption using the model. For modeling the protocol, we used the Markov chain model, derived the transmission and state probabilities, and obtained the equations to solve the performance of throughput, delay, and energy consumption. Our proposed model and analysis are validated by comparing numerical results obtained from the model, with simulation results using NS-2.

• 인터넷정보학회논문지
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• 제19권2호
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• pp.9-15
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• 2018

This paper proposes an energy efficient adaptive relay station ON/OFF scheme with different frequency reuse factors (FRFs) to enhance the system throughput and reduce the transmission energy consumption for the transparent mode of 2-hop cellular relay networks (CRNs) based on orthogonal frequency division multiple access and time division duplex. In the proposed scheme, the base station turns on or off the relay stations (RSs) when they are overutilized and undertuilized based on the traffic density of the cell coverage, respectively. Through the simulation results, we show that the proposed scheme outperforms the conventional CRN in terms of the energy consumption with the same system throughput. Further, in order to increase the system throughput with low energy consumption, the best way is FRF 1 when the number of operating RSs is up to 4 and FRF 2 otherwise.