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Hyungjune Bae,Yeonsik Kang 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10
This paper presents the development of an algorithm that uses nonlinear model predictive control (NMPC) to avoid collisions between a driver’s vehicle and the nearby vehicles in complex situations. In particular, the paths of the driver’s vehicle and the nearby vehicles are predicted to avoid collisions. NMPC is used to predict the paths of all vehicles, and if a collision is detected in the predicted path, the driver’s vehicle attempts to avoid the collision through a left lane change, right lane change, or braking maneuver. Several scenarios are implemented through MATLAB/Simulink simulations to verify the performance of the proposed algorithms when multiple vehicles are engaged in sudden lane change movements.
Joint Radio Selection and Relay Scheme through Optimization Model in Multi-Radio Sensor Networks
( Hyungjune Lee ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.12
We present joint radio selection and relay scheme that delivers data from a source to a sink in heterogeneous stationary sensor networks consisting of various radio interfaces. The proposed scheme finds the optimal relay nodes and their corresponding radio interfaces that minimize energy consumption throughout the network while satisfying the end-to-end packet deadline requirement. We formulate the problem of routing through radio interface selection into binary integer programs, and obtain the optimal solution by solving with an optimization solver. We examine a trade-off relationship between energy consumption and packet delay based on network level simulations. We show that given the end-to-end deadline requirement, our routing algorithm finds the most energy-efficient routing path and radio interface across mesh hops. We demonstrate that the proposed routing scheme exploits the given packet delivery time to turn into network benefit of reducing energy consumption compared to routing based on single radio interface.
Optimal Cell Selection Scheme for Load Balancing in Heterogeneous Radio Access Networks
HyungJune Lee(이형준) 한국통신학회 2012 韓國通信學會論文誌 Vol.37 No.12B
스마트폰의 급격한 보급에 따른 무선 접속망의 과부하 문제가 네트워크에서 중요한 문제로 부각되고 있다. 이 논문에서는 매크로 셀, 펨토 셀, 와이파이 접속망으로 다양하게 구성되어 있는 현재 이종 네트워크에서 접속망 과부하 문제를 해결하기 위한 최적의 셀 선정 기법과 리소스 할당 기법을 제안한다. 주어진 현재 서비스 부하 상태에서 네트워크가 동시에 추가 수용할 수 있는 사용자 수를 최대화할 수 있는 사용자-셀 간의 선정 기법을 제공한다. 이를 위해 이종 무선 접속망에서의 셀 선정 문제를 이진 정수계획 모형으로 최적화 문제를 수립하고, 이를 최적화 해법 도구를 이용하여 접속망 과부하를 억제할 수 있는 최적의 셀 선정 기법을 도출한다. 네트워크 레벨 시뮬레이션을 통해 이 논문에서 제안된 기법이 현재 무선 접속망에서 주로 사용되고 있는 국소적 셀 선정기법에 비해, 과부하가 걸린 무선 접속망에서 주어진 여러 셀들을 최대한 균등하게 효율적으로 활용함으로써 현저하게 네트워크 접속 장애율을 감소시킬 수 있음을 보인다. 또한 논문에서 사용된 이진 정수계획 모형의 최적화 문제를 푸는 데 소요되는 계산 복잡도에 대한 실험을 통해 제안된 알고리즘의 실용 가능성에 대해서 검증한다. We propose a cell selection and resource allocation scheme that assigns users to nearby accessible cells in heterogeneous wireless networks consisting of macrocell, femtocells, and Wi-Fi access points, under overload situation. Given the current power level of all accessible cells nearby users, the proposed scheme finds all possible cell assignment mappings of which user should connect to which cell to maximize the number of users that the network can accommodate at the same time. We formulate the cell selection problem with heterogeneous cells into an optimization problem of binary integer programming, and compute the optimal solution. We evaluate the proposed algorithm in terms of network access failure compared to a local ad-hoc based cell selection scheme used in practical systems using network level simulations. We demonstrate that our cell selection algorithm dramatically reduces network access failure in overload situation by fully leveraging network resources evenly across heterogeneous networks. We also validate the practical feasibility in terms of computational complexity of our binary integer program by measuring the computation time with respect to the number of users.
Predictive Data Delivery to Mobile Users Through Mobility Learning in Wireless Sensor Networks
HyungJune Lee,Wicke, Martin,Kusy, Branislav,Gnawali, Omprakash,Guibas, Leonidas IEEE 2015 IEEE Transactions on Vehicular Technology VT Vol.64 No.12
<P>We consider applications, such as indoor navigation, evacuation, or targeted advertising, where mobile users equipped with a smartphone-class device require access to sensor network data measured in their proximity. Specifically, we focus on efficient communication protocols between static sensors and users with changing location. Our main contribution is to predict a set of possible future paths for each user and store data at sensor nodes with which the user is likely to associate. We use historical data of radio connectivity between users and static sensor nodes to predict the future user-node associations and propose a network optimization process, i.e., data stashing, which uses the predictions to minimize network and energy overheads of packet transmissions. We show that data stashing significantly decreases routing cost for delivering data from stationary sensor nodes to multiple mobile users compared with routing protocols where sensor nodes immediately deliver data to the last known association nodes of mobile users. We also show that the scheme provides better load balancing, avoiding collisions and consuming energy resources evenly throughout the network, leading to longer overall network lifetime. Finally, we demonstrate that even limited knowledge of the location of future users can lead to significant improvements in routing performance.</P>
암호화된 클라우드 데이터의 중복제거 기법에 대한 부채널 공격
신형준(Hyungjune Shin),구동영(Dongyoung Koo),허준범(Junbeom Hur) 한국정보보호학회 2017 정보보호학회논문지 Vol.27 No.4
클라우드 환경에서 대량으로 발생하는 데이터들에 대해 효율적인 저장 공간을 제공하는 기법으로 단일의 데이터만을 저장하여 중복을 제거하는 중복제거 기법을 활용할 수 있다. 위탁 데이터에 대한 기밀성에 민감한 사용자들은 안전한 암호 알고리즘을 이용 가능하지만 중복제거 기법의 효율성을 떨어뜨린다는 단점을 가지고 있다. 사용자의 데이터 프라이버시를 보장하면서 저장 공간의 효율성을 올리기 위해 2015년에 PAKE(Password Authenticated Key Exchange) 프로토콜을 활용한 서버 측면의 사용자간 중복제거 기법이 제안되었다. 본 논문에서는 부채널을 통하여 제안된 기법이 CoF(Confirmation-of-File) 또는 중복 확인 공격(ducplicate identification attack)에 대해 안전하지 않음을 증명한다. Data deduplication can be utilized to reduce storage space in cloud storage services by storing only a single copy of data rather than all duplicated copies. Users who are concerned the confidentiality of their outsourced data can use secure encryption algorithms, but it makes data deduplication ineffective. In order to reconcile data deduplication with encryption, Liu et al. proposed a new server-side cross-user deduplication scheme by exploiting password authenticated key exchange (PAKE) protocol in 2015. In this paper, we demonstrate that this scheme has side channel which causes insecurity against the confirmation-of-file (CoF), or duplicate identification attack.
Greedy Data Transportation Scheme with Hard Packet Deadlines for Wireless Ad Hoc Networks
Hindawi Publishing Corporation 2014 THE SCIENTIFIC WORLD JOURNAL Vol.2014 No.-
<P>We present a greedy data transportation scheme with hard packet deadlines in ad hoc sensor networks of stationary nodes and multiple mobile nodes with scheduled trajectory path and arrival time. In the proposed routing strategy, each stationary ad hoc node en route decides whether to relay a shortest-path stationary node toward destination or a passing-by mobile node that will carry closer to destination. We aim to utilize mobile nodes to minimize the total routing cost as far as the selected route can satisfy the end-to-end packet deadline. We evaluate our proposed routing algorithm in terms of routing cost, packet delivery ratio, packet delivery time, and usability of mobile nodes based on network level simulations. Simulation results show that our proposed algorithm fully exploits the remaining time till packet deadline to turn into networking benefits of reducing the overall routing cost and improving packet delivery performance. Also, we demonstrate that the routing scheme guarantees packet delivery with hard deadlines, contributing to QoS improvement in various network services.</P>