• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.17-22
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• 2013

In this paper, we propose a multi-hop cooperative transmission protocol over Rayleigh fading channels. In the proposed protocol, the multi-hop cooperative transmission is used to improve the system performance. Due to broadcast nature, we do not limit the receiving node to be only the next node, but the destination and all the nodes between the transmitting node and the destination. The proposed protocol can hence save the average transmit power, compared with multi-hop direct transmission protocol due to the skipped transmissions from some intermediate nodes or chosen relays. The proposed scheme is implemented and evaluated in mobile ad-hoc wireless networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.620-629
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• 2012

This paper proposes packet aggregation scheme for considering energy consumption of mobile devices on guaranteeing quality of voice. To our purpose, we analyze VoIP service on wireless multi-hop channel in terms of delay, packet loss and energy consumption when packet aggregation scheme is applied to VoIP service. Moreover, we induce a cost function with considering of tradeoff relation between quality of voice and energy consumption.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06d
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• pp.258-261
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• 2010

VANET(Vehicular Ad hoc NETwork)에서 차량간(V2V) 무선 통신을 통해 긴급 메시지를 빠르고 정확하게 전송하기 위하여 거리와 밀도를 기반으로 최적의 전송 대기시간을 계산하고, 이를 기반으로 중계노드를 선정하여 전송지연을 줄이는 멀티홉 브로드캐스트 기법을 제안한다. 제안한 기법을 통하여 밀도가 낮은 환경에서도 전송 지연 없이 전체 네트워크에 전송할 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1084-1093
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• 2012

For large multihop networks, large time synchronization (TS) errors can accumulate with conventional methods, such as TPSN, RBS, and FTSP, since they need a large number of hops to cover the network. In this paper, a method combining Concurrent Cooperative Transmission (CCT) and Semi- Cooperative Spectrum Fusion (SCSF) is proposed to reduce the number of hops to cover the large network. In CCT, cooperating nodes transmit the same digitally encoded message in orthogonal channels simultaneously, so receivers can benefit from array and diversity gains. SCSF is an analog cooperative transmission method where different cooperators transmit correlated information simultaneously. The two methods are combined to create a new distributed method of network TS, called the Cooperative Analog and Digital (CANDI) TS protocol, which promises significantly lower network TS errors in multi-hop networks. CANDI and TPSN are compared in simulation for a line network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.372-380
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• 2009

In this paper, we analyze the active RFID systems ISO/IEC 18000-7 and ISO/IEC 18000-4. In order to improve the coverage in sensor networks, which consist active RFID tag, we propose RFID multi-hop relay system using active RFID relay tag. To compare the performance between the existing ISO/IEC 18000-7 system and the proposed RFID multi-hop relay system, we introduce new system efficiency measure and sensitivity-based measure of achieved coverage. Also, we analyze the performance of the proposed system and compare it with that of the existing system through MCL (Minimum Coupling Loss) analysis and SLS (System Level Simulation) analysis.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.17-22
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• 2011

In this paper, we analyze co-channel interference cancellation performance to be generated in multi-hop military communication system. First, remove interference using zero-forcing (ZF) and minimum mean square error (MMSE) scheme as interference cancellation methods, and then obtain additional diversity gain and improve interference cancellation performance by applying successive interference cancellation (SIC). We consider Rayleigh fading channel and system performance is analyzed as respect of bit error probability. From simulation results, we confirm MMSE improves significantly BER performance than ZF in multi-hop wireless network environment. It is also confirmed ZF and MMSE schemes applying SIC algorithm have better performance comparing to the existing schemes. Therefore, MMSE-SIC method can provide more reliable signal transmission in the multi-hop military communication system.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1297-1299
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• 2010

무선 통신에서는 무선 통신의 브로드캐스트한 특성으로 데이터의 기밀성 유지를 위한 암호화가 매우 중요하다. 특히 무선 센서 네트워크(WSN - Wireless Sensor Network)의 경우 일반적인 PC와는 다르게 다양한 환경에 위치할 수 있어 공격자에게 더 쉽게 노출 될 수 있는 문제점을 가지고 있다. 이런 환경에서 미리 저장된 해쉬 함수나 비밀 값에 의존한 키 분배를 할 경우 저장된 값이 노출될 경우 심각한 문제를 초래하게 된다. 그리고 D-H 키 분배 알고리즘의 경우 키 값을 안전하게 도출을 할 수 있지만 키를 도출한 대상에 대한 인증의 부재와 멀티 홉 환경에서 중간자 공격에 취약한 문제점을 드러내고 있다. 본 논문에서는 이런 문제를 해결하기위해 기존 연구를 응용하여 멀티 홉 환경에서 무선 통신의 특성을 이용한 비밀값 공유와 제 3의 노드를 이용한 간단한 인증이 가능한 기법을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2533-2540
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• 2013

In multihop cellular network environments, the mobility of nodes is a major obstacle to find a reliable routing path between a mobile node (MN) and the access node (AN). Therefore, in this paper, we propose a fast and reliable neighbor discovery protocol that enables the fast and reliable neighbor discovery by considering the node mobility in the multihop cellular network. The proposed neighbor discovery protocol inhibits the transmission of unnecessary control messages to quickly find a suitable neighbor node (NN) and performs a priority-based access control to transmit control messages without collision in the order of NN desirable to be selected. Simulation results show that the proposed neighbor discovery protocol can discover the NNs faster than the conventional scheme and select a more reliable relay node although the number of neighbor nodes increases and the node mobility increases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10B
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• pp.911-918
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• 2008

In this paper, we propose new cell structures using multi-hop Relay Station(RS) based on IEEE802.16j in Narrow-Beam Trisector Cell (NBTC) and Wide-Beam Trisector Cell (WBTC), which are two methods for cell sectorization using 3-sector directional antennas. Then, we analyze our proposed structures compared with the existing system which does not use any RS about the numbers of optimized Base Station (BS) and multi-hop relay, the extended BS coverage, and the deployment cost according to the traffic density using optimization model. According to the results, we know the reduction of total deployment cost of the proposed systems and that WBTC is suitable when the traffic density is high and NBTC is suitable when the traffic density is low in our proposed multi-hop based NBTC and WBTC structures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3A
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• pp.229-234
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• 2009

In this paper, we propose a decision scheme of amount of required resources in wireless multi-hop systems which can reuse radio resources adaptively among relay stations (RSs). Base stations (BSs) can allocate resources dynamically based on amount of required resources of each RS. Moreover using resource reuse with this allocation method can increase amount of available resources in multi-hop systems. Generally, BSs allocate same amount of resources for RSs which share and reuses same resources for each other. Since amount of required resources are different among these RSs, a decision scheme of a specific value which can represent various required resources of RSs is needed. We propose this scheme which can decide the representative value of required resources of RSs adaptively based on the amount of required resources and the buffer state of each RS. Our simulation results show that the proposed scheme can increase performance of a multi-hop system. System capacity with the proposed adaptive scheme is increased by twice as large as one with a fixed representation value.