• Journal of Communications and Networks
• /
• 제8권3호
• /
• pp.297-305
• /
• 2006

High-rate wireless personal area network (HR-WPAN) has been standardized by the IEEE 802.15.3 task group (TG). To support multimedia services, the IEEE 802.15.3 TG adopts a time-slotted medium access control (MAC) protocol controlled by a central device. In the time division multiple access (TDMA)-based wireless packet networks, the packet scheduling algorithm plays a key role in quality of service (QoS) provisioning for multimedia services. In this paper, we propose an adaptive cross-layer packet scheduling method for the TDMA-based HR-WPAN. Physical channel conditions, MAC protocol, link layer status, random traffic arrival, and QoS requirement are taken into consideration by the proposed packet scheduling method. Performance evaluations are carried out through extensive simulations and significant performance enhancements are observed. Furthermore, the performance of the proposed scheme remains stable regardless of the variable system parameters such as the number of devices (DEVs) and delay bound.

• 한국통신학회논문지
• /
• 제25권3B호
• /
• pp.456-463
• /
• 2000

Bidirectional cable TV networks using HFC(Hybrid Fiber Coaxial) networks need MAC (Medium access control) protocols to have efficient access in upstream channels. In this paper, we have studied and evaluated several contention resolution algorithms and mapping of higher layer traffic described in IEEE 802.14 and MCNS (Multimedial Cable Network System) MAC protocols with respect to IP, ABR and CBR traffic types. IEEE 802.14 MAC protocol demonstrates better performance for transmitting ATM cells while the MCNS MAC protocols for the IP traffic.

• 한국통신학회논문지
• /
• 제32권1A호
• /
• pp.34-43
• /
• 2007

In the IEEE 802.15.3 Medium Access Control (MAC) protocol, Simultaneously Operating Piconets (SOPs) are linked by the parent/child (P/C) or parent/neighbor (P/N) configuration, which work on a Time Division Multiple Access (TDMA) basis. This provides interference mitigation but the overall throughput is limited because the SOPs share the channel time exclusively. The protocol is not efficient for SOPs if we focus on the combination of interference mitigation and high throughput maintenance. In this paper Public Channel Time Allocation (Public CTA) is proposed, which is able to greatly reduce the inter-piconet interference (IPI) and achieve greater throughput without much loss of link success probability (LSP) in the SOPs. The simulation results based on the SOPs of Direct Sequence Ultra Wideband (DS-UWB) system demonstrate that the proposed scheme effectively supports the coexistence of SOPs, and it can not only significantly improve the overall throughput of SOPs but also maintain high LSP.

• 한국정보전자통신기술학회논문지
• /
• 제2권2호
• /
• pp.87-95
• /
• 2009

이 연구는 정보유통시스템으로 컴퓨터통신망에서 파일저장 장치의 보안과 인증시스템으로 설계하고 연구하려는 것으로 컴퓨터 정보처리에 이용되고 활용되어야 할 암호화된 정보와 데이터 파일 저장장치에 대한 보안을 유지되도록 사용자 이용권한(access)을 시스템적 접근 문제로 해결하려는 인증네트워크 시스템으로서, 1회용 암호와 네트워크 IP Tracking을 이용한 인증시스템의 설계를 연구하였다.

• Journal of the Optical Society of Korea
• /
• 제12권4호
• /
• pp.326-336
• /
• 2008

A WDM-PON has been considered as an ultimate solution for access networks. However, there were many technical and practical issues for commercial deployment. These issues were solved with wavelength locked F-P LD and the WDM-PONs employing this optical source were commercialized. These WDM-PON systems have been deployed in Korea, Europe, and US. We reviewed wavelength locking technology and WDM-PON achievements. When we inject spectrum sliced broadband light into an F-P LD, the multimode output is changed to a quasi single mode. Then, we can use the single mode light for WDM signal transmission. The broad spectral gain of the semiconductor gain medium enables a color-free operation of WDM-PON, i.e., an identical ONT can be used for each user. The wavelength locking properties depend on many parameters, especially alignment of injection wavelength to a lasing mode, passband profile of AWG and front facet reflectivity of F-P LD. However, these dependencies can be reduced by proper design of the laser and the injection bandwidth. Thus, WDM-PON systems have been achieved with color-free operation.

• International Journal of Advanced Culture Technology
• /
• 제9권3호
• /
• pp.238-242
• /
• 2021

Through diversification of 4th industries and transportation and globalization, tourism was developed for medical purposes, not limited to touring tourist attractions. The trend of medical tourism in Korea is shifting from large and medium-sized hospitals to professional medical services in one area of small hospitals rather than professional medical services. However, small hospitals lack medical coordinators and interpretation services, and tourists who visit Korea for treatment lack information on small hospitals. Therefore, a platform is needed to match small hospitals with medical tourists. In this study, using Platform as a Service (Paas) in cloud computing, clinic administrators can access the app to introduce information about their hospitals with simple manipulations. Tourists also want to propose a customized platform to select the right area for them to check information about small-scale hospitals and choose the treatment and tourist attractions they wants. In this study, using Platform as a Service (Paas) in cloud computing, clinic administrators can access the app to introduce information about their hospitals with simple manipulations.

• International Journal of Computer Science & Network Security
• /
• 제23권7호
• /
• pp.16-22
• /
• 2023

Enhanced radio access technologies (RAT) are deployed in Next Generation Convergence Networks by the service providers so as to satisfy the basic requirements of end-users for e.g. QoS. Whenever the available resources are being shared simultaneously and dynamically by multiple users or distribution of allocated channels randomly, the deficiency of spectral resources and dynamic behavior of Network traffic in real time Networking, we may have problem. In order to evaluate the performance of our proposed algorithm, computer simulation has been performed on NS-2 simulator and a comparison with the existing algorithms has been made.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제7권1호
• /
• pp.1-21
• /
• 2013

The release of IEEE 802.15.4e specification significantly develops IEEE 802.15.4. The most inspiring improvement is the enhancement for medium access control (MAC) sublayer. To study the performance of IEEE 802.15.4e MAC, in this paper we first present an overview of IEEE 802.15.4e and introduce three MAC mechanisms in IEEE 802.15.4e. And the major concern here is the Time Slotted Channel Hopping (TSCH) mode that provides deterministic access and increases network capacity. Then a detailed analytical Markov chain model for TSCH carrier sense multiple access with collision avoidance (CSMA-CA) is presented. Expressions which cover most of the crucial issues in performance analysis such as the packet loss rate, energy consumption, normalized throughput, and average access delay are presented. Finally the performance evaluation for the TSCH mode is given and we make a comprehensive comparison with unslotted CSMA-CA in non-beacon enabled mode of IEEE 802.15.4. It can validate IEEE 802.15.4e network can provide low energy consumption, deterministic access and increase network capacity.

• 한국정보통신학회논문지
• /
• 제19권1호
• /
• pp.50-60
• /
• 2015

수중 음향네트워크에서 노드의 위치와 이동속도에 따라 변화하는 전파지연 시간을 추정하여 시간 블록이라는 새로운 슬럿 단위로 노드들의 전송 스케줄을 설정하는 Block-Time-Bounded Time Division Multiple Access (BTB-TDMA) 매체접속제어 방식이 제안되었다. 본 논문에서는 노드의 이동으로 인해 상향(uplink)과 하향(downlink)의 전파지연이 비대칭적이 되고, 이에 따른 수신 충돌이 BTB-TDMA의 성능에 미치는 영향을 시뮬레이션을 통해 분석한다. 이를 위해 전파지연 비대칭성으로 인한 수신 충돌률, 채널접속지연, 채널효율을 수학적으로 모델링하고, 수중노드의 수, 네트워크 범위, 수중노드의 이동 속도에 따라 BTB-TDMA 시간 블록의 길이를 변화시켜 광범위한 시뮬레이션을 수행한다. 시뮬레이션 결과의 분석을 통해, 네트워크 환경에 따라 수신 충돌을 최소화 하면서, 채널 접속지연과 채널효율 성능을 최대화할 수 있는 시간 블록 값을 도출할 수 있는 성능지표를 제시한다.

• 전자공학회논문지A
• /
• 제32A권4호
• /
• pp.32-39
• /
• 1995

In this paper, a timer thresholds tuning algorithm is proposed, satisfying the required response time for traffic with time-critical applications and asynchronous traffic in FDDI network. Under light and medium load, priorities and timer thresholds play a minor role for medium access control. In these cases all quenes are served exhaustively with a ver high service probability and the packet loss probability approaches almost zero. Under overload condition, however, the performance of the FDDI Network is completely determined by the selection of the timer thresholds. The timer thresholds tuned by mathematical results is confirmed by simulation results using SIMAN/UNIX package. The allocation of guaranteed bandwidth can be controlled easily by tuning the timer thresholds according to the proposed rules.