• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2001.10a
• /
• pp.129-132
• /
• 2001

The ad hoc network was composed of Mobile hosts. Due to the limited transmission range of each mobile node hosts, in such an environment, it is essential for other hosts to coorperate to transfer packet to destination. Moreover, the existing routing protocol algorithms are not efficient on the ad hoc network because a mobile host operates router without fixed router. In this paper, we will compare and analysis for the performance of existing ad hoc network routing protocols through simulation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.10
• /
• pp.2620-2633
• /
• 1996

In this paper, a new high-speed local area network using a dual mode switching access (DMSA) protocol implemented on a dual unidirectional bus is described. By utilizing the implicit positionalordering of stations on a unidirectional bus, the proposed system switches between random access mode and the token access model withoug unnecessary delay. Therefore, unlike other hybrid systems such as Buzz-net and Z-net, DMSA does not show a rapid degradation in performance as the load increases. We obtain the average channel utilization and the average access delay by using a simplified analytic model. The numerical results obtained via analysis are compared to the simulation resuls for a partial validation of the approximate model. The performance characteristics of DMSA are superior delay-throughput characteristics at light and medium loads, compared to compared to other LAN systems, and the capability of providing a single active station with full capabity of the channel.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2000.10b
• /
• pp.1181-1184
• /
• 2000

정보통신 분야의 급격한 발달은 다양한 프로토콜을 지원하는 통신 시스템의 개발 주기를 더욱 빠르게 하고 있으며, 통신 프로토콜의 체계적인 분석과 재사용성 및 확장성을 고려한 시스템의 모델링 방법에 대한 필요성을 증가시키고 있다. 본 논문에서는 이에 대한 방안으로 객체지향 방법을 이용한 프로토콜의 시스템 모델링 및 설계 방안을 제시하였다. 이를 위해 WAP(Wireless Application Protocol)의 WTP를 객체지향 모델링 언어인 UML과 통신 시스템의 명세서를 작성하고 설계하는 표준화된 언어인 SDL을 이용하여 분석하고 설계하였다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2016.04a
• /
• pp.330-332
• /
• 2016

제한된 자원을 사용하는 IoT디바이스들 간에 통신을 위한 다양한 경량 프로토콜이 개발되었다. 하지만 IoT의 의미는 디바이스 간의 통신을 넘어 인터넷과의 통신을 의미하면서 HTTP와 같은 비경량 프로토콜을 사용하는 서비스들 하고의 연동을 위해서는 경량 프로토콜(CoAP, MQTT, XMPP)을 비경량 프로토콜(HTTP) 혹은 그 반대로 프로토콜 변환을 위해 크로스 프로토콜 프록시가 필요로 해졌다. 본 논문에서는 크로스 프로토콜 프록시에서의 보안을 분석한다.

• Journal of the Ergonomics Society of Korea
• /
• v.23 no.1
• /
• pp.49-63
• /
• 2004

In this study. differences in attention allocation patterns between expert and novIce pilots were investigated by a verbal protocol when pilots were engaged in a task during the instrument flight. Ten pilots including experts and novices were participated to conduct a pre-determined task(a fix-to-fix) on F-5E Cockpit Procedure Trainer Simulator. Experts show better performance as expected with more stable variations in speed. altitude. and attitude. In attention allocation patterns. novices allocated about 83% of attentional resources on the primary instruments (airspeed indicator. altitude indicator. and attitude) relating to the task of the basic flight while experts spent 57%. This difference in the availability of attentional resources allowed expert pilots to accomplish the task better than novices. In other words. training a pilot should consider a program for building up wider instrument scanning patterns to become an expert in a shorter time.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.29A no.7
• /
• pp.10-18
• /
• 1992

In this paper, a simulation model for scope and filter parameters in CMIS/CMIP, OSI management protocol, has been discussed and the suitable scope type was represented by analyzing optimal polling time in network management system, queue size and response time. Scope and filter parameters in MGet, M-Set, M-Action, and =M-Delete services provide a scheme to select some managed objects, and the results are largely varied according to a scope type requested and the outcome of filtering. It has been simulated each scope type and all scope type mixed in a network by varying the offered load and a polling time. On the same time, the response time, queue size of the managing system and a delay time have been measured. As a results, the suitable scope type and polling time enhancing the network performance on the OSI network management is proposed.

• Journal of Communications and Networks
• /
• v.8 no.3
• /
• pp.351-359
• /
• 2006

In this article, we present a new slow-start variant, which improves the throughput of transmission control protocol (TCP) Vegas. We call this new mechanism Gallop-Vegas because it quickly ramps up to the available bandwidth and reduces the burstiness during the slow-start phase. TCP is known to send bursts of packets during its slow-start phase due to the fast window increase and the ACK-clock based transmission. This phenomenon causes TCP Vegas to change from slow-start phase to congestion-avoidance phase too early in the large bandwidth-delay product (BDP) links. Therefore, in Gallop-Vegas, we increase the congestion window size with a rate between exponential growth and linear growth during slow-start phase. Our analysis, simulation results, and measurements on the Internet show that Gallop-Vegas significantly improves the performance of a connection, especially during the slow-start phase. Furthermore, it is implementation feasible because only sending part needs to be modified.

• Journal of Communications and Networks
• /
• v.14 no.1
• /
• pp.40-50
• /
• 2012

The Berkeley-medium access control (B-MAC) is a lightweight, configurable and asynchronous duty cycle medium access control (MAC) protocol in wireless sensor networks. This article presents an analytic modelling of single-hop B-MAC protocol under a Poisson traffic assumption.Our model considers important B-MAC parameters such as the sleep cycle, the two stage backoff mechanism, and the extended preamble. The service delay of an arriving packet and the energy consumption are calculated by an iterative method. The simulation results verify that the proposed analytic model can accurately estimate the performance of single-hop B-MAC with different operating environments.

• Journal of Korean Institute of Industrial Engineers
• /
• v.35 no.4
• /
• pp.248-256
• /
• 2009

In this paper, under saturated traffic condition in a single-hop wireless sensor network, we present an analytic model that evaluates the performance of asynchronous MAC protocol which uses a preamble technique. Our model considers the impact of several important factors such as sleep cycle, the backoff mechanism and the number of contending nodes. After obtaining the cumulative backoff time of a sending node and expected delay of a receiving node, an iterative algorithm is presented for calculating the performance measures such as expected energy consumption usage per packet and latency. Simulation results show that the proposed analytic model can accurately estimate the performance measures under saturated traffic conditions.

• Journal of Communications and Networks
• /
• v.14 no.5
• /
• pp.510-517
• /
• 2012

This paper analyzes the performance of voice-over-Internet protocol (VoIP) services in terms of the system throughput, the packet delay, and the signaling overhead in a mobile WiMAX system with a hybrid automatic repeat request (HARQ) mechanism. Furthermore, a queueing analytical model is developed with due consideration of adaptive modulation and coding, the signaling overhead, and the retransmissions of erroneous packets. The arrival process is modeled as the sum of the arrival rate at the initial transmission queue and the retransmission queue, respectively. The service rate is calculated by taking the HARQ retransmissions into consideration. This paper also evaluates the performance of VoIP services in a mobile WiMAX system with and without persistent allocation; persistent allocation is a technique used to reduce the signaling overhead for connections with a periodic traffic pattern and a relatively fixed payload. As shown in the simulation results, the HARQ mechanism increases the system throughput as well as the signaling overhead and the packet delay.