• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.6 s.348
• /
• pp.23-29
• /
• 2006

It is difficult to apply conventional security algorithms to the wireless sensor networks composed of nodes that have resource constraints such as memory, computing, power resources limitation. Generally, shared key based algorithms with low resource consumption and short key length are used for broadcast packets in authentication of base station. But it is not suitable that all the nodes hold the same shared key only for packet authentication. Recently, broadcast authentication algorithm for sensor network is proposed, which uses key chain generation by one-way hash function, Message Authentication Code generation by each keys of the key chains and delayed key disclosure. It provides suitable authentication method for wireless sensor networks but may leads to inefficient consequence with respect to network conditions such as broadcast ratio, key chain level, and so on. In this paper, we propose an improved broadcast authentication algorithm that uses key chain link and periodical key disclosure. We evaluated the performance of proposed algorithm using TOSSIM(TinyOS Simulator) in TinyOS. The results show that the proposed algorithm ensures low authentication delay, uses memory and computing resource of receiving nodes efficiently and reduces the amount of packet transmitting/receiving.

• Journal of Internet Computing and Services
• /
• v.17 no.4
• /
• pp.11-17
• /
• 2016

In this paper, we proposed a multi-viewer system with multiple HD cameras based AVB(Audio Video Bridge) ethernet cable using IP networking, and FPGA(Xilinx Zynq 702) for bus safety systems. This AVB (IEEE802.1BA) system can be designed for the low latency based on FPGA, and transmit real-time with HD video and audio signals in a vehicle network. The proposed multi-viewer platform can multiplex H.264 video signals from 4 wide-angle HD cameras with existed ethernet 1Gbps. and 2-wire 100Mbps cables. The design of Zynq 702 based low latency to H.264 AVC CODEC was proposed for the minimization of time-delay in the HD video transmission of car area network, too. And the performance of PSNR(Peak Signal-to-noise-ratio) was analyzed with the reference model JM for encoding and decoding results in H.264 AVC CODEC. These PSNR values can be confirmed according the theoretical and HW result from the signal of H.264 AVC CODEC based on Zynq 702 the multi-viewer with multiple cameras. As a result, proposed AVB multi-viewer platform with multiple cameras can be used for the surveillance of audio and video around a bus for the safety due to the low latency of H.264 AVC CODEC design.

• The KIPS Transactions:PartC
• /
• v.8C no.1
• /
• pp.60-67
• /
• 2001

Multicast Protocol for multimedia service on the Internet can be classified into two types, e.g., source based tree and shared tree according to difference of tree construction method. Shared tree based multicast is known to show outstanding results in the aspect of scalability than source based tree. Generally, There have been lots of researches on the method to satisfy QoS constraints through proper Rendezvous Point (RP) in the shared tree. In addition, as the multicast group members join and leave dynamically in the service time, RP of the shared tree should b be reselected for guranteeing Qos to new member, But, RP reselection method has not been considered generally as the solution to satisfy QoS C constraints. In this paper, new initial RP selection and RP reselection method are proposed, which utilize RTCP (Real Time Control Protocol) report packet fields. Proposed initial RP selection and RP reselection method use RTCP protocol which underlying multimedia application service So, the proposed method does not need any special process for collecting network information to calculate RP. New initial RP selection method s shows better performance than random and topology based one by 40-50% in simulation. Also, RP reselection method improves delay p performance by 50% after initial RP selection according to the member’s dynamicity.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.1
• /
• pp.237-245
• /
• 1997

In this paper, a flow control mechanism is proposed which is based on the priority control between communication path of a node. In this scheme, demanding length of a data queue for any pre-defined, then each node in that path is forced to maintains buffer size under the limit by controlling priority level of the path. The communication path which requires higher bandwidth sets its demanding queue length smaller. By providing relationship between the priority of a path and length of its queue, the high bandwidth requesting path has a better chance to get high bandwidth by defining the smaller demanding queue size. And also, by forcing a path which has high flow rate to maintain small queue size in the path of the communication, the scheme keep the transmission delay of the path small. The size of the demanding queue of a path is regularly adjusted to meet the applications requirement, and the load status of the network during the life time of the communication. The priority control based on the demanding queue size is also provided in the intermediate nodes as well as the end nodes. By that the flow control can provide a quicker result than end to-end flow control, it provides better performance advantage especially for the high speed network.

• The KIPS Transactions:PartD
• /
• v.10D no.4
• /
• pp.591-602
• /
• 2003

Delay and discontinuance phenomenon of service are cause by sudden increase of the network communication amount and the quantity consumed of resources when Internet users are driven excessively to a conventional single large database sewer. To solve these problems, spatial database cluster consisted of several single nodes on high-speed network to offer high-performance is risen. But, research about spatial join operation that can reduce the performance of whole system in case process at single node is not achieved. So, in this paper, we propose efficient parallel spatial join processing method in a spatial database cluster system that uses data partitions and replications method that considers the characteristics of space data. Since proposed method does not need the creation step and the assignment step of tasks, and does not occur additional message transmission between cluster nodes that appear in existent parallel spatial join method, it shows performance improvement of 23% than the conventional parallel R-tree spatial join for a shared-nothing architecture about expensive spatial join queries. Also, It can minimize the response time to user because it removes redundant refinement operation at each cluster node.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.12
• /
• pp.1039-1047
• /
• 2017

This paper presents a test development of a Fly-By-Wireless flight control system for a fixed-wing unmanned aerial vehicle (UAV). Fly-By-Wireless system (FBWLS) refers to a system that uses a wireless network instead of a wired network to connect sensors and actuators with a flight control computer (FCC), reducing considerable amount of wires. FBWLS enables to design a much lighter aircraft along with decreased maintenance time and cost. In this research we developed a Zigbee-based FWBLS UAV in which sensors (GPS and AHRS) are wirelessly connected via a FCC to aileron and elevator servo motors. In order to see the effect of time delay due to wireless signal on the flight stability of the UAV, several flight tests were conducted. From the tests, it was confirmed that the effect is minor by comparing the flight response of the FBWLS with the corresponding Fly-By-Wire system.

• Journal of KIISE:Computer Systems and Theory
• /
• v.26 no.8
• /
• pp.984-998
• /
• 1999

최근 개인 휴대 통신에 대한 관심도가 증가하면서 B-ISDN (Broadband Integrated Services Digital Network)과 같은 기존의 유선 망에서 제공하던 다양한 멀티미디어 응용 지원을 무선 망으로 확장시키기 위한 연구가 활발히 진행되고 있다. 그러나 기존의 유선 망에서는 멀티미디어 응용 지원을 위해 QoS (Quality of Service) Provisioning에 관한 많은 연구가 되어 있으나 무선 망에서는 이동성과 무선 전파의 열악한 전송으로 인해 새로운 QoS Provisioning 방법에 관한 연구가 필수적이다. 본 논문에서는 이러한 무선 망의 특수성으로 인해 발생할 수 있는 서비스의 질 저하와 강제 종료를 줄임으로써 지속적인 QoS를 보장해 주고 한정된 무선 자원을 효율적으로 사용하며 처리에 의한 오버헤드를 줄이기 위하여 다음과 같은 세 가지 방법을 제안하였다. 첫째, 핸드오프 강제 종료율을 줄이기 위하여 대역폭 예약 방법을 사용하되 특정 셀의 트래픽 특성에 맞게 또한 시간대에 따른 트래픽 특성에 따라 예약 대역폭의 양을 조절하는 적응적 대역폭 예약 방법이다. 둘째, 많은 경우 각 셀의 트랙픽 변화는 일정한 주기로 변화한다는 특성에 따라 과거의 트래픽 정보를 이용하는 예측 기반의 대역폭 예약 방법이다. 마지막으로 호의 종류, 트래픽 특성, 단말기의 이동 속도에 따라 다른 우선 순위에 의해 호 수락 제어를 수행하는 우선 순위 기반의 호 수락 제어를 제안하였다. 시뮬레이션을 통하여 기존에 제안된 방법과 성능 비교하여, 요구되는 수준의 QoS 보장과 효율적인 자원의 사용, 요구되는 처리비용의 최소화를 통해 전체 시스템의 성능 향상을 입증하였다.Abstract As interest in wireless hand-held terminals and in personal communications services increases recently, there have been broad studies on the ways to support multimedia applications provided in wired networks such as B-ISDN (Broadband Integrated Services Digital Network) in wireless networks. However, since many studies have focused on Quality of Service (QoS) Provisioning in wired networks to provide multimedia applications, new methods of QoS Provisioning are needed in wireless networks to resolve the problem of wireless channel fading and the difficulty of mobility occurred in wireless networks. This paper proposes three schemes of QoS Provisioning in wireless networks which will make continuous QoS guarantee and efficient use of limited wireless resources possible. The first scheme reserves bandwidth in proportion to the amount of real-time traffic in the neighbor cells to decrease the handoff dropping rate of delay sensitive real-time connections, adapting reserved bandwidth for efficient resource utilization. The second scheme is predictive bandwidth reservation scheme that utilizes the past handoff information. It can decrease overheads required to adapt bandwidth reservation. The last scheme is priority-based call admission control prioritizing traffic type (real-time traffic/ non-real-time traffic), connection type (new connection /handoff connection), and mobile terminal speed (fast mobile/slow mobile). Simulation results show that the proposed QoS Provisioning schemes improve the total system performance by achieving three goals - required QoS guarantee, higher bandwidth utilization and less overhead.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.4B
• /
• pp.323-332
• /
• 2006

In this paper, we consider a WDM based metro ring connecting broadband access networks by using FT-TR (Fixed Transmitter-Tunable Receiver) type access nodes and a new MAC protocol for fair transmission is proposed. The basic channel access scheme is CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) and the transferred optical slot is changed to be empty slot by SS(Source-Stripping) which drops a packet from ring-rotated slot. This empty slot can be either used to send head-of-line packet in buffer or transmitted to next access node. In former cases, there is the improvement of network throughput, but latter case leads unfairness problem of transmission. Thus the proposed MAC protocol exploits the advantages form tow cases. It gives downstream access nodes chance to use empty slots and limits the unconditional usage of empty slots at upstream access nodes with probability as called p-Persistent MAC protocol. We use a numerical analysis to evaluate bandwidth efficiency and maximum node throughput and compares simulation results in terms of node throughput, fairness factor, transfer delay depending on probability. Under two different FT-TR type architectures for metro ring network the proposed MAC protocol is evaluated and compared.

• Journal of IKEEE
• /
• v.5 no.2 s.9
• /
• pp.136-145
• /
• 2001

As with appearing new applications that requires QoS guarantee such as VoIP, VPN in Internet, problems of IP QoS has been one of most important issues in next-generation Internet. IETF has proposed integrated services model(Int-Serv) and differentiated service(Diff-Serv) to supply IP QoS in Internet. Int-Serv model uses the state information of each IP flow, so satisfies QoS according to traffic characteristics, but increases the amount of flow state information with increasing flow number. Diff-Serv model uses PHP(Per Hop Behavior), and there are well-defined classes to provide differentiated traffics with different services according to delay and loss sensitivity. Diff-Serv model can provide diverse services in Internet because of having no the state and signal information of each flow. As MPLS uses the packet forwarding technique based-on label, it implements the traffic engineering in the networks easily. The MPLS can set up the path with different traffic parameters, and assign each path to particular Class of Services. Therefore it is possible to support the Diff-Serv model with well-defined classes. In this paper we investigate the performance improvement of Diff-Serv function in the MPLS network to guarantee class of services in Internet.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.17 no.4
• /
• pp.54-62
• /
• 2018

As a part of realization of artificial intelligence signal(AI Signal), this study proposed an actuated signal algorithm based on vehicle queue length that estimates in real time by deep learning. In order to implement the algorithm, we built an API(COM Interface) to control the micro traffic simulator Vissim in the tensorflow that implements the deep learning model. In Vissim, when the link travel time and the traffic volume collected by signal cycle are transferred to the tensorflow, the vehicle queue length is estimated by the deep learning model. The signal time is calculated based on the vehicle queue length, and the simulation is performed by adjusting the signaling inside Vissim. The algorithm developed in this study is analyzed that the vehicle delay is reduced by about 5% compared to the current TOD mode. It is applied to only one intersection in the network and its effect is limited. Future study is proposed to expand the space such as corridor control or network control using this algorithm.