• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권8호
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• pp.3789-3808
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• 2017

This paper studies a multi-antenna wireless relay network in the presence of a jammer. In this network, the source node transmits signals to the destination node through a multi-antenna relay node which adopts the amplify-and-forward scheme, and the jammer attempts to inject additive signals on all antennas of the relay node. With the linear beamforming scheme at the relay node, this network can be modeled as an equivalent Gaussian arbitrarily varying channel (GAVC). Based on this observation, we deduce the mathematical closed-forms of the capacities for two special cases and the suboptimal achievable rate for the general case, respectively. To reduce complexity, we further propose an optimal structure of the beamforming matrix. In addition, we present a second order cone programming (SOCP)-based algorithm to efficiently compute the optimal beamforming matrix so as to maximize the transmission rate between the source and the destination when the perfect channel state information (CSI) is available. Our numerical simulations show significant improvements of our propose scheme over other baseline ones.

• 한국군사과학기술학회지
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• 제19권3호
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• pp.356-362
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• 2016

IEEE 802.16 standard(WiMAX) is one of 3.5G/4G wireless technologies and there are many systems based on the standard. Each frame of the systems begins with a preamble for synchronization and channel estimation, etc. IEEE 802.16 standard defines a total of 114 preamble sequences. By the way there are some systems(such as mobile multi-hop relay) that require using more than 114 preamble sequences. So we define 114 additional preamble sequences in this paper. And we evaluate PAPR and cross-correlation performance of them to decide to be usable as a preamble.

• Journal of Information Processing Systems
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• 제2권1호
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• pp.39-43
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• 2006

In this paper, we proposed TASL-MAC, a medium-access control (MAC) protocol for wireless sensor networks. In wireless sensor networks, sensor nodes are usually deployed in a special environment, are assigned with long-term work, and are supported by a limited battery. As such, reducing the energy consumption becomes the primary concern with regard to wireless sensor networks. At the same time, reducing the latency in multi-hop data transmission is also very important. In the existing research, sensor nodes are expected to be switched to the sleep mode in order to reduce energy consumption. However, the existing proposals tended to assign the sensors with a fixed Sleep/Listening schedule, which causes unnecessary idle listening problems and conspicuous transmission latency due to the diversity of the traffic-load in the network. TASL-MAC is designed to dynamically adjust the duty listening time based on traffic load. This protocol enables the node with a proper data transfer rate to satisfy the application's requirements. Meanwhile, it can lead to much greater power efficiency by prolonging the nodes' sleeping time when the traffic. We evaluate our implementation of TASL-MAC in NS-2. The evaluation result indicates that our proposal could explicitly reduce packet delivery latency, and that it could also significantly prolong the lifetime of the entire network when traffic is low.

• 한국인터넷방송통신학회논문지
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• 제9권4호
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• pp.47-52
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• 2009

Source로부터 송신된 신호는 무선 채널을 통하여 Destination에 전달된다. 하지만 이동하는 Destination이 Source의 Coverage를 벗어난 경우나 비록 Source의 Coverage 내의 음영 지역에 Destination이 존재하는 경우, Destination은 Source로부터 송신된 신호를 수신할 수 없고 통신을 할 수 없게 된다. 따라서 이러한 문제점을 극복하기 위해 중계기가 사용된다. 이와 같이 중계기를 사용하는 시스템을 다중 홉 중계 (Multi-hop Relay) 시스템이라 한다. 그런데 다중 홉 중계 시스템에서는 서로 다른 시스템용 중계기의 Coverage가 겹치는 경우가 발생할 수 있고, 이 부분에 Destination이 존재하는 경우 Destination에는 간섭이 발생한다. 본 논문에서는 다중 홉 중계 시스템에서 발생 할 수 있는 동일 채널 간섭 (CCI : Co-Channel Interference) 제거 방법에 관해 연구하였다. 간섭 제거 방법은 우선 Zero Forcing (ZF) 또는 Minimum Mean Square Error (MMSE) 개념을 적용한 선형 수신기를 이용하여 간섭을 제거한 후, 정렬된 연속간섭제거 (OSIC : Ordered Successive Interference Cancellation) 알고리즘을 이용하여 추가적인 다이버시티 이득을 얻고 간섭 제거 성능을 향상시킨다. 무선 채널은 레일레이 (Rayleigh) 페이딩 채널을 고려하여 모의 실험을 하였으며, 시스템 성능은 비트 오류 확률 (Bit Error Probability) 측면에서 분석되었다.

• 한국산업정보학회논문지
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• 제22권1호
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• pp.1-9
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• 2017

무선 네트워크 기술과 무선 전송 기술의 발전으로 인해 무선 전달망(Wireless Transit Network) 구성 기술로서 무선 메시 네트워크(WMN)가 관심을 받고 있다. 오랜 기간 다양한 영역에서 WMN에 대한 연구가 진행되었지만 아직 해결되지 않은 문제들이 많이 남아있다. 그 중 하나가 무선 링크로 구성된 다중 홉 네트워크에서 최적 경로를 찾는 라우팅 문제이다. WMN의 3가지 구성유형 중 하나인 하이브리드 WMN에서 최적 경로 선택을 위해서는 우수한 성능의 메트릭 연구와 함께 효과적으로 인프라스트럭처 메시를 전달망으로 사용하기 위한 경로 검색 프로토콜 연구가 필요하다. 따라서 본 논문에서는 하이브리드 WMN을 위한 듀얼모드-AODV(Ad hoc On-demand Distance Vector)를 제안한다. 본 논문에서 제안된 듀얼모드-AODV를 하이브리드 WMN에 적용하는 경우 AODV에 비하여 경로 검색 지연시간이 52% 감소하는 것을 시뮬레이션을 통해 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권9호
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• pp.3034-3055
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• 2014

Wireless Sensor Networks have extensively been utilized for ambient data collection from simple linear structures to dense tiered deployments. Issues related to optimal resource allocation still persist for simplistic deployments including linear and hierarchical networks. In this work, we investigate the case of dimensioning parameters for linear and tiered wireless sensor network deployments with notion of providing extended lifetime and reliable data delivery over extensive infrastructures. We provide a single consolidated reference for selection of intrinsic sensor network parameters like number of required nodes for deployment over specified area, network operational lifetime, data aggregation requirements, energy dissipation concerns and communication channel related signal reliability. The dimensioning parameters have been analyzed in a pipeline monitoring scenario using ZigBee communication platform and subsequently referred with analytical models to ensure the dimensioning process is reflected in real world deployment with minimum resource consumption and best network connectivity. Concerns over data aggregation and routing delay minimization have been discussed with possible solutions. Finally, we propose a node placement strategy based on a dynamic programming model for achieving reliable received signals and consistent application in structural health monitoring with multi hop and long distance connectivity.

• 한국군사과학기술학회지
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• 제23권4호
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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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권7호
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• pp.1547-1568
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• 2013

Wireless body area network (WBAN) is an emerging short-range wireless communication network with sensor nodes located on, in or around the human body for healthcare, entertainment and ubiquitous computing. In WBANs, energy is severely constrained which is the prime consideration in the medium access control (MAC) protocol design. In this paper, we propose a novel MAC protocol named Energy-efficient Relay MAC with dynamic Power Control (ERPC-MAC) to save energy consumption. Without relying on the additional devices, ERPC-MAC employs relaying nodes to provide relay service for nodes which consume energy fast. Accordingly the superframe adjustment is performed and then the network topology can be smoothly switched from single-hop to multi-hop. Moreover, for further energy saving and reliability improvement, the dynamic power control is introduced to adjust the power level whenever a node transmits its packets to the coordinator or the relaying node. To the best of the authors' knowledge, this is the first effort to integrate relay, topology adjustment and power control to improve the network performance in a WBAN. Comprehensive simulations are conducted to evaluate the performance. The results show that the ERPC-MAC is more superior to the existing standard and significantly prolongs the network lifetime.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권1호
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• pp.74-96
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• 2023

At present, the smart grid has become one of the indispensable infrastructures in people's lives. As a commonly used communication method, wireless communication is gradually, being widely used in smart grid systems due to its convenient deployment and wide range of serious challenges to security. For the insecurity of the schemes based on large integer factorization and discrete logarithm problem in the quantum environment, an identity-based key management scheme for smart grid over lattice is proposed. To assure the communication security, through constructing intra-cluster and inter-cluster multi-hop routing secure mechanism. The time parameter and identity information are introduced in the relying phase. Through using the symmetric cryptography algorithm to encrypt improve communication efficiency. Through output the authentication information with probability, the protocol makes the private key of the certification body no relation with the distribution of authentication information. Theoretic studies and figures show that the efficiency of keys can be authenticated, so the number of attacks, including masquerade, reply and message manipulation attacks can be resisted. The new scheme can not only increase the security, but also decrease the communication energy consumption.

• 한국산업정보학회논문지
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• 제10권2호
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• pp.13-20
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• 2005

Ad Hoc 네트워크는 잦은 망 구성의 변화, 라우터의 수, 제한된 사용 자원 등 기존 유선 네트워크와는 다른 특성들을 가지게 된다. 따라서 기존의 유선 네트워크에서 사용하던 라우팅 프로토콜들을 Ad Hoc 네트워크에 그대로 적용시킨다면 많은 문제점들이 발생하게 된다. 본 논문에서 제안하는 라우팅 프로토콜은 Ad Hoc 네트워크의 특성을 고려하여, 네트워크 내의이동 호스트를 멀티 홉을 갖는 클러스터로 묶고, 클러스터 헤드로 하여금 자신의 멤버 호스트들과 이웃 클러스터들의 헤드 정보를 유지하게 하여, 경로 설정에 대한 요구가 있을 때에 적은 지연 시간과 적은 패킷으로 목적지까지의 최단 경로를 설정할 수 있도록 한다. 또한 경로 설정과 데이터 전송 모두가 클러스터 헤드를 이용한다. 이러한 경우 모든 데이터와 경로 설정 시 발생하는 패킷들이 클러스터 헤드로 집중되어 네트워크 부하가 발생하게 되는데 본 제안에서는 네트워크의 부하를 줄이기 위하여 후보 클러스터 헤드를 이용하는 방법을 제시한다.