• 한국컴퓨터정보학회논문지
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• 제10권6호
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• pp.227-232
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• 2005

개방형 통신망에서 CVR, VBR, UBR, ABR과 같은 다양한 트래픽 관리 및 지연에 관한 연구가 진행되고 있고 특히 패킷 스위치 기반의 망에서는 대역폭 확장 및 트래픽 관리를 통한 망의 효율적이며 유연한 품질 서비스를 제공한다. 이러한 품질 서비스에는 멀티미디어 패킷을 전송하기 위하여 트래픽 QoS를 고려한 서비스가 제공되어야 하며 이에 대한 연구가 진행되고 있다. 본 논문에서는 패킷 스위치 망에 들어오는 패킷들을 안정성 기준으로 등급 평가한다. 다량의 비안전성 등급 패킷은 네트워크 혼잡을 피하기 위하여 허용치를 기준으로 전송 또는 폐기함으로서 멀티미디어 네트워크의 QOS 를 향상시키다. 본 논문은 패킷 스위치 기반에서 패킷을 폐기 할때 발생하는 패킷 지연에 관한 연구 및 시뮬레이션 시나리오를 제공한다.

• 한국컴퓨터정보학회논문지
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• 제10권5호
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• pp.245-250
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• 2005

개방형 통신망에서 CVR, VBR, UBR, ABR과 같은 다양한 트래픽 관리 및 지연에 관한 연구가 진행되고 있고 특히 패킷 스위치 기반의 망에서는 대역폭 확장 및 트래픽 관리를 통한 망의 효율적이며 유연한 품질 서비스를 제공한다. 이러한 품질 서비스에는 멀터미디어 패킷을 전송하기 위하여 트래픽 QoS를 고려한 서비스가 제공되어야 하며 이에 대한 연구가 진행되고 있다. 본 논문에서는 패킷 스위치 망에 들어오는 패킷들을 안정성 기준으로 등급 평가한다. 다량의 비안전성 등급 패킷은 네트워크 혼잡을 피하기 위하여 허용치를 기준으로 전송 또는 폐기함으로서 멀티미디어 네트워크의 QoS를 향상시키다. 본 논문은 패킷 스위치 기반에서 패킷을 패기 할 때 발생하는 패킷 지연에 관한 연구 및 시뮬레이션 시나리오를 제공한다.

• 한국멀티미디어학회논문지
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• 제20권7호
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• pp.1030-1037
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• 2017

Traffic flows of real-time multimedia services such as Internet phone and IPTV are bounded on the end-to-end delay. Packets violating their delay limits will be dropped at a router because of not useful anymore. Service providers promise the quality of their providing services in terms of SLA(Service Level Agreement), and they, especially, have to guarantee the packet loss rates listed in the SLA. This paper is about a method to guarantee the required packet loss rate of each traffic flow keeping the high network resource utilization as well. In details, it assures the required loss rate by adjusting adaptively the timestamps of packets of the flow according to the difference between the required and measured loss rates in the lossy Weighted Fair Queuing(WFQ) scheduler. The proposed method is expected to be highly applicable because of assuring the packet loss rates regardless of the fluctuations of offered traffic load in terms of quality of services and statistical characteristics.

• Journal of Communications and Networks
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• 제16권1호
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• pp.36-44
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• 2014

Exploiting the energy-delay tradeoff for energy saving is critical for developing green wireless communication systems. In this paper, we investigate the delay-constrained energy-efficient packet transmission. We aim to minimize the energy consumption of multiple randomly arrived packets in an additive white Gaussian noise channel subject to individual packet delay constraints, by taking into account the practical on-off circuit power consumption at the transmitter. First, we consider the offline case, by assuming that the full packet arrival information is known a priori at the transmitter, and formulate the energy minimization problem as a non-convex optimization problem. By exploiting the specific problem structure, we propose an efficient scheduling algorithm to obtain the globally optimal solution. It is shown that the optimal solution consists of two types of scheduling intervals, namely "selected-off" and "always-on" intervals, which correspond to bits-per-joule energy efficiency maximization and "lazy scheduling" rate allocation, respectively. Next, we consider the practical online case where only causal packet arrival information is available. Inspired by the optimal offline solution, we propose a new online scheme. It is shown by simulations that the proposed online scheme has a comparable performance with the optimal offline one and outperforms the design without considering on-off circuit power as well as the other heuristically designed online schemes.

• ETRI Journal
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• 제28권1호
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• pp.31-44
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• 2006

In a packet switching network, congestion is unavoidable and affects the quality of real-time traffic with such problems as delay and packet loss. Packet fair queuing (PFQ) algorithms are well-known solutions for quality-of-service (QoS) guarantee by packet scheduling. Our approach is different from previous algorithms in that it uses hardware time achieved by sampling a counter triggered by a periodic clock signal. This clock signal can be provided to all the modules of a routing system to get synchronization. In this architecture, a variant of the PFQ algorithm, called digitized delay queuing (DDQ), can be distributed on many line interface modules. We derive the delay bounds in a single processor system and in a distributed architecture. The definition of traffic contribution improves the simplicity of the mathematical models. The effect of different time between modules in a distributed architecture is the key idea for understanding the delay behavior of a routing system. The number of bins required for the DDQ algorithm is also derived to make the system configuration clear. The analytical models developed in this paper form the basis of improvement and application to a combined input and output queuing (CIOQ) router architecture for a higher speed QoS network.

• 전자공학회논문지S
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• 제35S권3호
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• pp.65-75
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• 1998

We consider connection-oriented wireless cellular networks such as the second generation wireless cellular networks and wirelss ATM networks. In these networks, a separate forward signaling channel is provided for the transmission of paging and channel allocation packets. When a call destined to a user is requested, all the base stations in the user's current location area broadcast the corresponding paging packet across forward signaling channels. By slot mode operation and paging group allocation for fusers in a location area, we can reduce relative power consumption level at battery-operated terminals. However, a sthe number of paging groups is increased for lowering relative power consumption level, a paging packet experiences higher delay to access the forward signaling channel. For the pre-negotiated quality-of-service level, paging packet delay level must be limited. In this paper, we consider static and dynamic multiplexing schemes for paging packets, and develop an analytical method for calculating paging packet delay and relative power consumption levels. Using this analytial method, we investigate the effect of network parameters on the paging packet delay and relative power consumption levels.

• Journal of Communications and Networks
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• 제16권6호
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• pp.656-666
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• 2014

In delay tolerant networks (DTNs), delay is inevitable; thus, making better use of buffer space to maximize the packet delivery rate is more important than delay reduction. In DTNs, epidemic routing is a well-known routing protocol. However, epidemic routing is very sensitive to buffer size. Once the buffer size in nodes is insufficient, the performance of epidemic routing will be drastically reduced. In this paper, we propose a buffer scheme to optimize the performance of epidemic routing on the basis of the Lagrangian and dual problem models. By using the proposed optimal buffer scheme, the packet delivery rate in epidemic routing is considerably improved. Our simulation results show that epidemic routing with the proposed optimal buffer scheme outperforms the original epidemic routing in terms of packet delivery rate and average end-to-end delay. It is worth noting that the improved epidemic routing needs much less buffer size compared to that of the original epidemic routing for ensuring the same packet delivery rate. In particular, even though the buffer size is very small (e.g., 50), the packet delivery rate in epidemic routing with the proposed optimal buffer scheme is still 95.8%, which can satisfy general communication demand.

• 한국통신학회논문지
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• 제24권10B호
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• pp.1852-1860
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• 1999

본 논문에서는 음성 패킷을 전송하기 위해 새로 제시되어 표준화된 AAL2의 성능을 이산 시간 시뮬레이션 모형(discrete-time simulation model)을 통해 분석하였다. 시뮬레이션의 입력 파라메터로는 AAL2 PDU를 만들기 위한 패킷 필 지연 시간(packet fill delay), 여러 AAL2 PDU로부터 ATM 셀을 만들기 위한 셀 생성 지연(guard time), 음성 트래픽의 특성을 정의하는 버스트 정도(burstness), 그리고 사용자 수(number of channels)로 하였으며 이 값의 변화에 따른 음성 패킷의 양종단 지연 시간 변이(end-to-end delay variation)을 계산하여 각각의 파라미터가 음성 패킷의 성능에 미치는 영향을 분석하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권4호
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• pp.1006-1025
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• 2012

Improving the quality of service in IP networks is a major challenge for real-time voice communications. In particular, packet arrival-delay variation, so-called "jitter," is one of the main factors that degrade the quality of voice in mobile devices with the voice-over Internet protocol (VoIP). To resolve this issue, a receiver-based enhanced timing recovery algorithm combined with active jitter estimation 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. Extensive simulations have shown that the proposed algorithm delivers high voice quality by pursuing an optimal trade-off between average buffering delay and packet loss rate.

• 한국통신학회논문지
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• 제34권5B호
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• pp.498-508
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• 2009

3GPP(3rd Generation Partnership Project)에서 표준화 중인 LTE(Long Term Evolution) 시스템은 고품질의 다양한 서비스를 제공하기 위한 차세대 이동통신 기술로써, 최근 LTE 시스템의 무선자원 사용효율을 향상시키기 위한 하향링크 스케줄링 기법 연구가 활발하게 수행되고 있다. 본 논문에서는 무선 채널 상태나 공정성뿐만 아니라 다양한 트래픽 종류의 지연에 대한 QoS 요구사항을 보장하기 위해서 지연 가중치(delay weight) 함수를 적용한 DAPS(Delay-Aware Packet Scheduling) 알고리즘을 제안한다. DAPS 알고리즘은 패킷의 큐잉 지연이 허용되는 최대 지연에 가까울수록 지연 가중치를 증가시켜 높은 우선순위를 제공함으로써 최대 허용 지연 이내에 처리되는 패킷의 수를 증가시킨다. 모의실험 결과 DAPS 알고리즘은 기존 스케줄링 알고리즘과 비교하여 전송되는 패킷의 큐잉 지연이 최대 허용되는 지연을 초과할 확률을 최소화하여 패킷 지연에 관한 성능을 개선하였다.