• Proceedings of the KIEE Conference
• /
• 2001.07d
• /
• pp.1990-1992
• /
• 2001

In this paper, a NeuroFuzzy controller (NFC) with enhanced packet reservation multiple access (PRMA) protocol for QoS-guaranteed multimedia communication systems is proposed. The enhanced PRMA protocol adopts mini-slot technique for reducing contention cost, and these minislot are futher partitioned into multiple MAC regions for access requests coming from users with their respective QoS (quality-of-service) requirements. And NFC is designed to properly determine the MAC regions and access probability for enhancing the PRMA efficiency under QoS constraint. It mainly contains voice traffic estimator including the slot information estimator with recurrent neural networks (RNNs) using real-time recurrent learning (RTRL), and fuzzy logic controller with Mandani- and Sugeno-type of fuzzy rules. Simulation results show that the enhanced PRMA protocol with NFC can guarantee QoS requirements for all traffic loads and further achieves higher system utilization and less non real-time packet delay, compared to previously studied PRMA, IPRMA, SIR, HAR, and F2RAC.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.10
• /
• pp.4015-4033
• /
• 2015

The future mobile networks consist of hyper-dense heterogeneous and small cell networks of same or different radio access technologies (RAT). Integrating mobile networks of different RATs to provide seamless and smooth mobility service will be the target of future mobile converged network. Generally, handover from high-speed networks to low-speed networks faces many challenges from application perspective, such as abrupt bandwidth variation, packet loss, round trip time variation, connection disruption, and transmission blackout. Existing inter-RAT handover solutions cannot solve all the problems at the same time. Based on the high-layer convergence sublayer design, a new receiver-aided soft inter-RAT handover is proposed. This soft handover scheme takes advantage of multihoming ability of multi-mode mobile station (MS) to smooth handover procedure. In addition, handover procedure is seamless and applicable to frequent handover scenarios. The simulation results conducted in UMTS-WiMAX converged network scenario show that: in case of TCP traffics for handover from WiMAX to UMTS, not only handover latency and packet loss are eliminated completely, but also abrupt bandwidth/wireless RTT variation is smoothed. These delightful features make this soft handover scheme be a reasonable candidate of mobility management for future mobile converged networks.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.1
• /
• pp.68-78
• /
• 2013

In this paper, we propose an early spectrum sensing(ESS) as an advance preparation for radio-access trial, which enables multi-mode terminals to access the most appropriate radio-access system in a cloud-conceptual base station system where multiple radio access technologies(RATs) coexist. Prior to a random access to one of RATs, a multi-mode terminal conducts a spectrum sensing over entire frequency bands of whole RATs, then select the RAT with the lowest sensing power, that is likely to have the most available spectrum. Thus, an access failure caused by that the selected RAT has no available radio spectrum could be avoidable in advance. In computer simulation, we consider as various RATs as possible. First, circuit and packet systems are taken into consideration. In addition, the packet systems are classified according to the feasibility of carrier aggregation(CA). In case of terminal, three modes are considered with circuit-only, packet-only, and multi-mode. Subsequently, packet traffic is classified into real-time and non-real-time traffic with three different tolerable delay levels. The simulation includes a call process starting with a call generation and ending up with a resource allocation reflecting individual user's QoS requirements and evaluates the proposed scheme in terms of the successful access probability, system access time, system balancing factor and packet loss probability.

• The Journal of the Korea Contents Association
• /
• v.5 no.1
• /
• pp.73-79
• /
• 2005

Recent advances on wireless technology are enabling the design and deployment of real-time traffic in wireless LAN. Point Coordination Function (PCF) mode of Wireless LAN is defined to provide QoS of real time traffic, such as voice, video in wireless LANs. The service polling scheduling plays an important role in real-time traffic services of wireless LAN. This paper proposes a multicast polling scheme to increase the maximum number of conversations by reducing the amount of empty polls in IEEE 802.11 PCF mode. Our simulation studies show that our scheme may improve performance of the PCF in terms of the average transfer delay and packet discard ratio.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.11 no.1
• /
• pp.25-39
• /
• 1986

In this paper, we analyze the performance, particularly the flow control mechanism, of the CCITT X.25 protocol in a packet-switched network. In this analysis, we consider the link and packet layers separately, and investigate the performance in three measures; normalized channel throughput, mean transmission time, and transmission efficiency. Each of these measures is formulated in terms of given protocol parameters such as windos size, $T_1$ and $T_2$ values, message length, and so forth. We model the service procedure of the inpur traffic based on the flow control mechanism of the X.25 protocol, and investigate the mechanism of the sliding window flow control with the piggybacked acknowlodgment scheme using a discrete-time Markov chain model. With this model, we study the effect of variation of the protoccol parameters on the performance of the X.25 protocol. From the numerical results of this analysis one can select the optimal valuse of the protocol parameters for different channel environments. it has been found that to maintain the trasnmission capacity satisfactorily, the window size must be greater than or equal to 7 in a high-speed channel. The time-out value, $T_1$, must carefully be selected in a noisy channel. In a normal condition, it should be in the order of ls. The value of $T_2$ has some effect on the transmission efficiency, but is not critical.

• Quality Improvement in Health Care
• /
• v.3 no.1
• /
• pp.144-152
• /
• 1996

Background : Because of introduction of nationwide health care system in 1989 and the improvement of socioeconomic status of population the number of outpatient visiting university hospital has good facilities and manpower has increased. So the waiting time for medical service at university hospital are lengthened. Particularly outpatients complain that waiting for prescribed drugs at pharmacy depart are long. Reducing waiting time at pharmacy depart door-to-door delivery system that the patients applying for door-to-door delivery receive prescribed drug at home without waiting at pharmacy depart were studied. The objective of this study is to analysis the opinion of outpatients for door-to-door delivery system, to study the appropriateness of adopting the system and to produce ideal model for the system. Method : Outpatients waiting drug at pharmacy depart were questioned about door-to-door delivery system. to find the factors affect utilizing the system the logistic regression was used. Result : 83.3% of the patients want to utilize the system without charging, and 72.9% of the patients want to utilized system with charging. 68.3% of patients with charging want to use this system because of long waiting time at pharmacy depart. 50% of patients who do not want to use door-to-door do not use this system because of incorrect delivery. The affecting factors to utilize the system were sex, waiting time, fee. Conclusion : The model for door to door delivery system. 1. door-to-door personnel reside in hospital and the patient want to utilize the system apply for the delivery with charging. 2. The applied drugs dispense at spare time. 3. Delivery company gathers drug at appointed time and delivers. 4. The delivery fee is 2,000-3,000 won. 5. To prevent from loss and changing the drug the name of patient on packet are printed and drug packet are sealed. 6. The company submit the confirm sheet which are written that the patient received drug correctly to hospital. 7. The delivery time of drug is reserved for the convenience of receiving.

• Proceedings of the IEEK Conference
• /
• 2000.06c
• /
• pp.149-152
• /
• 2000

In the Internet, multimedia data transfer is hard to guarantee the characteristics of the Real-Time because of the Best-Effort of the nature of IP, then additional mechanism is applied to multimedia application for real-time data. In this paper, we introduce the nature of multimedia and the necessary facility for real-time protocol. We propose protocol layer, which has necessary function above mentioned and offer the end-to-end transfer far real-time data. Also, the proposed protocol perform a next low operation: 1) a required information for QoS control by using Feedback mechanism is obtained from sender, 2) divided a transferred packet by delay and loss priority. 3) recognized the low service models, and 4) decided a bandwidth and QoS according to a network state

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.2
• /
• pp.127-137
• /
• 2015

Various services such as IPTV(Internet Protocol TV), Internet Telephony are provided through multiple ISPs(Internet Service Providers) as ICT technologies are evolving. This paper suggests that the end-to-end Internet service quality evaluation method, which is optimized for domestic environment based on international standards. The end-to-end service quality determines the quality of IPTV and Internet Telephony services and is critical factor for subjective quality as well. As a result, time delay, jitter and packet loss rate are three elements for the quality evaluation. It is also shown that these factors can be predicted with traditional statistical method by sharing minimum amount of information between ISPs.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.4C
• /
• pp.295-307
• /
• 2002

The IEEE 1394 protocol is a de facto standard in multimedia digital home network. It supports several advanced features such as hot plugging, dynamic network reconfiguration, isochronous transmission and so on. Since the IEEE 1394 was adapted in the field of multimedia service with QoS guarantee, back bone network protocol with reel-time digital instrumentation and control sub networks, and physical layer protocol for real-time middleware such as real-time CORBA, the additional real-time features has been required in device driver implementation because of the necessity of the predictability enhancement. To guarantee the real-time features, the device driver of the IEEE 1394 should support the priority based packet processing and also need a isochronous buffer management mechanism to deal with the periodic isochronous communication. In this paper, we proposed a new software architecture of the IEEE 1394 device driver for supporting the real-time characteristics such as priority based packet processing, priority based scheduling and so on.

• Journal of Korea Society of Industrial Information Systems
• /
• v.16 no.5
• /
• pp.21-30
• /
• 2011

In this paper, we propose a real-time service based on retransmission slot in low rate WPAN. In the proposed scheme, during the communication period of the beacon-enabled mode in LR-WPAN standard, a special GTSs is dynamically assigned for retransmission of the packet that fails during a real-time service such as voice. This provides a time diversity in the severe channel error environments to support the required QoS. Analytical results show that this scheme achieves a much higher throughput and better transmission success rate per GTS slot than conventional schemes such as a common reserved scheme in LR WPAN.