• Journal of Positioning, Navigation, and Timing
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• v.2 no.1
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• pp.91-100
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• 2013

This paper introduces an indoor sensor fusion wireless communication device which provides the Location Based Service (LBS) using fire prevention facility. The proposed system can provide information in real time by optimizing the hardware of Wi-Fi technology. The proposed system can be applied to a fire prevention facility (i.e., emergency exit) and provide information such as escape way, emergency exit location, and accident alarm to smart phone users, dedicated terminal holders, or other related organizations including guardians, which makes them respond instantly with lifesaving, emergency mobilization, etc. Also, the proposed system can be used as a composite fire detection sensor node with additional fire and motion detect sensors.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.11
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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.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.397-410
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• 2016

This paper proposes a novel cooperative localization method for distributed wireless networks in 3-dimensional (3D) global positioning system (GPS) denied environments. The proposed method, which is referred to as hybrid ellipsoidal variational algorithm (HEVA), combines the use of non-parametric belief propagation (NBP) and variational Bayes (VB) to benefit from both the use of the rich information in NBP and compact communication size of a parametric form. InHEVA, two novel filters are also employed. The first one mitigates non-line-of-sight (NLoS) time-of-arrival (ToA) messages, permitting it to work well in high noise environments with NLoS bias while the second one decreases the number of calculations. Simulation results illustrate that HEVA significantly outperforms traditional NBP methods in localization while requires only 50% of their complexity. The superiority of VB over other clustering techniques is also shown.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8A
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• pp.769-774
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• 2006

Based on the performance of a cooperative diversity with selection combining in Rayleigh fading, the power control range of a relay node is investigated. Also the effect of the power-limited relay node to the system performance is investigated. If the average signal-to-noise ratio(SNR) of each signal path is equal, the single relay cooperative diversity is obtained 13.5dB gain at the outage probability of $1{\times}10^{-3}$ in Rayleigh fading. We noticed that the limited power of a relay node severely degrades the system performance. Therefore the node with limited power in ad-hoc network is not recommended as a relay node in cooperative diversity system.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.121-129
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• 2014

The trend of an increasing demand for a high-quality user experience, coupled with a shortage of radio resources, has necessitated more advanced wireless techniques to cooperatively achieve the required quality-of-experience enhancement. In this study, we investigate the critical problem of rate splitting in heterogeneous cellular networks, where concurrent transmission, for instance, the coordinated multipoint transmission and reception of LTE-A systems, shows promise for improvement of network-wide capacity and the user experience. Unlike most current studies, which only deal with spectral efficiency enhancement, we implement an optimal rate splitting strategy to improve both spectral efficiency and energy efficiency by exploring and exploiting cooperation diversity. First, we introduce the motivation for our proposed algorithm, and then employ the typical cooperative bargaining game to formulate the problem. Next, we derive the best response function by analyzing the dual problem of the defined primal problem. The existence and uniqueness of the proposed cooperative bargaining equilibrium are proved, and more importantly, a distributed algorithm is designed to approach the optimal unique solution under mild conditions. Finally, numerical results show a performance improvement for our proposed distributed cooperative rate splitting algorithm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.3
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• pp.47-55
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• 2008

본 논문에서는 모바일 ad-hoc 무선 센서 네트워크[1]에서 안정된 경로의 설정 및 설정된 경로의 lifetime 을 효과적으로 지원하여 데이터 전송효율을 향상시키기 위한 협력 도움 라우팅 프로토콜(CARP: Cooperative_Aided Routing Protocol) 을 제안한다. 제안된 라우팅 프로토콜의 기본 아이디어 및 특징은 다음과 같다. 첫째, 소스노드와 목적지 노드 사이의 안정된 라우팅 경로의 설정이다. 본 연구에서는 모바일 노드들의 이동성 정보를 이용한 엔트로피 기반의 안정된 경로 설정방법을 제안 사용한다. 둘째, 협력도움 전송 방법이다[3][4][5]. 설정된 경로 위로 데이터 패킷을 전송 할 때 경로 lifetime과 SNR의 효과적인 지원으로 데이터 전송률을 증가시키기 위해 이웃 노드들로부터 협력 도움을 받는다. 셋째, 기존의 센서 네트워크는 주로 고정된 노드 환경에서 많은 연구가 되어 왔지만, 본 연구에서는 노드들의 이동성을 고려한 환경에서 연구가 이루어진다. 제안된 CARP 의 성능평가는 OPNET(Optimized Network Engineering Tool)을 사용하여 이루어졌으며 성능평가를 통하여 제안한 프로토콜은 안정된 경로의 설정 및 데이터 전송효율을 효과적으로 증가 시킬 수 있음을 알 수 있다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.61-65
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• 2014

In this paper, we propose a method using cooperative spectrum sensing to avoid multipath and frequency selective fading. One of methods in conventional scheme was multi input multi output (MIMO) solution. However, in the wireless environment, mobile device hardly supports multi antenna because of limitation of hardware. Motivated from above problems, the proposed method provides the information of excellent channel to transmitter. As a result, quality of service (QoS) required by users can be satisfied. Finally, performance of the proposed protocol is analyzed in term of bit error rate (BER).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.11
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• pp.3738-3760
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• 2022

Due to increasing spectrum demand for new wireless devices applications, cooperative spectrum sensing (CSS) paradigm is the most promising solution to alleviate the spectrum shortage problem. However, in the interweave cognitive radio (CR) system, the inherent nature of CSS opens a hole to Byzantine attack, thereby resulting in a significant drop of the CSS security and efficiency. In view of this, a weighted differential sequential single symbol (WD3S) algorithm based on MATLAB platform is developed to accurately identify malicious users (MUs) and benefit useful sensing information from their malicious reports in this paper. In order to achieve this, a dynamic Byzantine attack model is proposed to describe malicious behaviors for MUs in an interweave CR system. On the basis of this, a method of data transmission consistency verification is formulated to evaluate the global decision's correctness and update the trust value (TrV) of secondary users (SUs), thereby accurately identifying MUs. Then, we innovatively reuse malicious sensing information from MUs by the weight allocation scheme. In addition, considering a high spectrum usage of primary network, a sequential and differential reporting way based on a single symbol is also proposed in the process of the sensing information submission. Finally, under various Byzantine attack types, we provide in-depth simulations to demonstrate the efficiency and security of the proposed WD3S.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.6
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• pp.1511-1519
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• 2010

In this paper, we proposed and analyzed a RSSI based cooperative localization algorithm considering wireless propagation characteristics in indoor and outdoor environments for wireless sensor networks, which can estimate the BN position. The conventional RSSI based estimation scheme has low precision ranging due to instability propagation characteristics by time variable. Hence, we implemented ray-launching simulator for analysis of propagation characteristics in 4 case, and experimented proposed localization scheme with 4 RN and 1 to 5 BN. Simulation results show that NLCA has estimation error as 2m-3.5m, however, proposed CLA/ECLA has 1.3m-2.5m/0.5m-1.2m by same environments. Therefore, if we can consider channel characteristics, the proposed algorithm provides higher localization accuracy than RSSI based conventional one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.766-773
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• 2007

Conventional wireless sensor network(WSN) has limited power and bandwidth. In order to develop multimedia sensor technology, high data rate communication systems are required. Cooperative communication system can help to decrease power consumption through spatial diversity. In cooperative transmission, one partner node assists one sensor node to transmit their data to destination. Instead of using M partners for M sensor nodes, we propose 1 partner for M sensor nodes. Proposed protocol offers similar diversity order as conventional one with much less bandwidth and hardware. It is able to almost reduce scattered nodes interference using orthogonal sub-carriers. In addition, we examined a power allocation between sensor nodes and relay that optimize the system performance.