• The Journal of the Acoustical Society of Korea
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• v.33 no.2
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• pp.133-138
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• 2014

Packet arrival-delay variation, so-called 'jitter' is one of the main factors that degrade the quality of voice in mobile devices at the Voice over Internet Protocol (VoIP). To resolve this issue, a playout scheduling based on adaptive jitter estimation for enhancing VoIP speech quality is proposed. The proposed algorithm copes with the effect of transmission jitter by expanding or compressing each packet according to the predicted network delay and variations. Additionally, the active network jitter estimation incorporates rapid detection of delay spikes and reacts to changes in network conditions. The experimental results have shown that the proposed algorithm delivers high voice quality in unstable network environment.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.261-266
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• 2007

UMTS release 5 에서 소개된 HSDPA 를 위해 도입된 새로운 기술 Adaptive Modulation and Coding, Hybrid Automatic Repeal reQuest, Fast Packet Scheduling 에 대해 알아보고 여기서 key role 이 되는 Fast Packet Scheduling 알고리즘 가운데 대표적인 세 가지 Round Robin(RR), Promotional Fairness(PF), Maximum Channel Quality Index(Max CQI) 알고리즘의 성능을 시스템 수율과 공평성의 관점에서 분석해보았다. 시스템 수율에서는 Max CQI, PF. RR 알고리즘 순이었으며 공평성 측면에서는 RR, PF Max CQI 알고리즘 순으로 나타났다. 같은 시스템, 같은 망 구조 내에서라면 알고리즘을 최적화하여 QoS와 성능을 극대화할 수 있도록 지속적인 연구가 필요하다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.762-771
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• 2005

In this paper, an efficient Adaptive quality-of-service (QoS) traffic control scheme with priority scheduling is proposed for the multimedia traffic transmission over wireless access networks. The objective of the proposed adaptive QoS control (AQC) scheme is to realize end-to-end QoS, to be scalable without the excess signaling process, and to adapt dynamically to the network traffic state according to traffic flow characteristics. Here, the reservation scheme can be used over the wireless access network in order to get the per-flow guarantees necessary for implementation of some kinds of multimedia applications. The AQC model is based on both differentiated service model with different lier hop behaviors and priority scheduling one. It consists of several various routers, access points, and bandwidth broker and adopts the IEEE 802.1 le wireless radio technique for wireless access interface. The AQC scheme includes queue management and packet scheduler to transmit class-based packets with different per hop behaviors (PHBs). Simulation results demonstrate effectiveness of the proposed AQC scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3A
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• pp.261-270
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• 2007

The Delay Threshold-based Priority Queueing (DTPQ) scheme has been shown useful for scheduling both real-time (RT) and non-real-time (NRT) service traffic in mobile broadband wireless access (MBWA) systems. The overall system capacity can be maximized subject to their QoS requirement by the DTPQ scheme, which takes the urgency of the RT service into account only when their head-of-line (HOL) packet delays exceed a given delay threshold. In practice, the optimum delay threshold must be configured under the varying service scenarios and a corresponding traffic load, e.g., the number of RT and NRTusers in the system. In this paper, we propose an adaptive version of DTPQ scheme, which updates the delay threshold by taking the urgency and channel conditions of RT service users into account. By evaluating the proposed approach in an orthogonal frequency division multiple access/time division duplex (OFDM/TDD)-based broadband mobile access system, it has been found that our adaptive scheme significantly improves the system capacity as compared to the existing DTPQ scheme with a fixed delay threshold.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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• pp.5800-5818
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• 2018

Interference may occur when several co-located wireless body area networks (WBANs) share the same channel simultaneously, which is compressed by resource scheduling generally. In this paper, a QoS-aware Adaptive Coloring (QAC) scheduling algorithm is proposed, which contains two components: interference sets determination and time slots assignment. The highlight of QAC is to determine the interference graph based on the relay scheme and adapted to the network QoS by multi-coloring approach. However, the frequent resource assignment brings in extra energy consumption and packet loss. Thus we come up with a launch condition for the QAC scheduling algorithm, that is if the interference duration is longer than a threshold predetermined, time slots rescheduling is activated. Furthermore, based on the relative distance and moving speed between WBANs, a prediction model for interference duration is proposed. The simulation results show that compared with the state-of-the-art approaches, the QAC scheduling algorithm has better performance in terms of network capacity, average delay and resource utility.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.15-16
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• 2018

본 논문에서는 다수의 센서 노드로 구성된 Internet of Things (IoT) 환경에서 새로운 환경에 대해 적응하는데 걸리는 시간을 줄이기 위한 새로운 스케줄링 기법을 제안한다. IoT 환경에서는 데이터 수집 및 전송 패턴이 사전에 정의되어 있지 않기 때문에 기존 정적인 Packet scheduling 기법으로는 한계가 있다. Q-learning은 네트워크 환경에 대한 사전지식 없이도 반복적 학습을 통해 Scheduling policy를 확립할 수 있다. 본 논문에서는 기존 Q-learning 스케줄링 기법을 기반으로 각 큐의 패킷 도착률에 대한 bound 값을 이용해 Q-table과 Reward table을 초기화 하는 새로운 Q-learning 스케줄링 기법을 제안한다. 시뮬레이션 결과 기존 기법에 비해 변화하는 패킷 도착률 및 서비스 요구조건에 적응하는데 걸리는 시간이 감소하였다.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.512-517
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• 2018

Improving voice quality is a major concern in telecommunications. In this paper, we propose a robust speech quality enhancement against background noise and packet loss at VoIP (Voice-over-IP) receiver. The proposed method combines network jitter estimation based on hybrid Markov chain, adaptive playout scheduling using the estimated jitter, and speech enhancement based on restoration of amplitude and phase to enhance the quality of the speech signal arriving at the VoIP receiver over IP network. The experimental results show that the proposed method removes the background noise added to the speech signal before encoding at the sender side and provides the enhanced speech quality in an unstable network environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12B
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• pp.719-727
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• 2007

The Wireless Mesh Network technology is able to provide an infrastructure for isolated islands, in which it is difficult to install cables or wide area such as battlefield of armed forces. Therefore, Wireless Mesh Network is frequently used to satisfy needs for internet connection and active studies and research on them are in progress However, as a result of increase in number of hops under hop-by-hop communication environment has caused a significant decrease in throughput and an increase in delay. Considering the heavy traffic of real-time data, such as voice or moving pictures to adaptive WMN, in a military environment, it is restricted for remote units to have their Mesh Node to get real-time services. Such phenomenon might cause an issue in fairness. In order to resolve this issue, the Location-based Packet Scheduling Scheme, which can provide an fair QoS to each mesh node that is connected to each echelon's AP and operates based on WRR method that gives a priority to emergency message and control packet. The performance of this scheme is validated.

• Journal of Communications and Networks
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• v.6 no.1
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• pp.68-77
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• 2004

In the near future packet networks should support applications which can not predict their traffic requirements in advance, but still have tight quality of service requirements, e.g., guaranteed bandwidth, jitter, and packet loss. These dynamic characteristics mean that the sources can be made to modify their data transfer rates according to network conditions. Depending on the customer&; needs, network operator can differentiate incoming connections and handle those in the buffers and the interfaces in different ways. In this paper, dynamic QoS-aware scheduling algorithm is presented and investigated in the single node case. The purpose of the algorithm is in addition to fair resource sharing to different types of traffic classes with different priorities ?to maximize revenue of the service provider. It is derived from the linear type of revenue target function, and closed form globally optimal formula is presented. The method is computationally inexpensive, while still producing maximal revenue. Due to the simplicity of the algorithm, it can operate in the highly nonstationary environments. In addition, it is nonparametric and deterministic in the sense that it uses only the information about the number of users and their traffic classes, not about call density functions or duration distributions. Also, Call Admission Control (CAC) mechanism is used by hypothesis testing.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.209-210
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• 2018

본 논문에서는 IIoT 환경에서 효율적인 긴급 데이터 패킷 처리를 위한 스케쥴링 방식을 제안한다. 이는 weighted round robin 스케쥴링에 기반하고, 비선점형 시스템에 적용하는 방식으로 처리한다. 긴급 데이터의 평균 큐 사이즈에 따라 적응형으로 중요도를 조절함으로써 최적화시킨다. 이는 적은 패킷 손실률과 작은 딜레이로 이어진다. 이 적응형 스케쥴링 방식은 갑작스런 처리량의 변화에 많은 패킷 손실률과 딜레이 증가량 없이 대처하는 것에 효율적인 해결책이 될 것으로 기대된다.