• 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.

• Journal of Communications and Networks
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• 제11권3호
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• pp.297-305
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• 2009

Multiprotocol label switching (MPLS) networks require dynamic flow admission control to guarantee end-to-end quality of service (QoS) for each Internet protocol (IP) traffic flow. In this paper, we propose to tackle the joint routing and admission control problem for the IP traffic flows in MPLS networks without rerouting already admitted flows. We propose two mathematical programming models for this problem. The first model includes end-to-end delay constraints and the second one, end-to-end packet loss constraints. These end-to-end QoS constraints are imposed not only for the new traffic flow, but also for all already admitted flows in the network. The objective function of both models is to minimize the end-to-end delay for the new flow. Numerical results show that considering end-to-end delay (or packet loss) constraints for all flows has a small impact on the flow blocking rate. Moreover, we reduces significantly the mean end-to-end delay (or the mean packet loss rate) and the proposed approach is able to make its decision within 250 msec.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제2권3호
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• pp.103-110
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• 2013

논리 노력[1, 2]의 기법은 회로의 지연 값을 간단한 필산으로 신속하게 측정할 수 있는 기술이다. 이 기법은 설계 공정 시간을 절약하는 장점도 있지만 고정 지연이라는 조건에서 논리 경로의 면적이나 전력 소비를 최소화하여 설계할 수 없는 단점이 있다. 이 단점을 보완하는 방법을 논문[3]에서 제안하였지만, 논리 경로가 하나인 회로에만 국한되어 적용할 수 있는 방법이었다. 본 논문에서는, 균형 지연 모델을 기초로, 다중 논리 경로의 회로에 적용할 수 있는 향상된 게이트 크기 결정 방법을 제한하고자 한다. 시뮬레이션 결과, 기존 논리노력 방법과 비교하면 전력 소비 측면에서 거의 같았지만 회로의 설계 공간 측면에서는 약 52%의 효율성을 보였다.

• 한국정보전자통신기술학회논문지
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• 제9권4호
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• pp.330-336
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• 2016

본 논문에서는 원하는 정보 신호를 추정하기 위해서 수정 Bartlett방법에 대해서 연구하였다. Bartlett방법은 구속 장을 1로 설정하고, 시간지연을 보상하여 원하는 정보 신호를 추정하는 방법이다. 수정 Bartlett방법은 최적 가중치 갱신치를 지연시간 보상에 적용하여 최적의 도래방향 신호를 추정하는 방법이다. 최적가중치는 선형구속최소분산 방법을 사용하였다. 모의실험을 이용하여 본 연구에서 제안한 방법과 기존 Bartlett 과 MUSIC방법의 성능을 비교 분석한다. 모의실험조건은 배열 안테나 소자 수 6개와 9개, 원하는 정보신호 3개[-15o, 0o, 15o]에서 원하는 신호를 추정한다. 원하는 정보 신호 추정에서 본 연구에서 제안한 방법이 기존의 Bartlett 과 MUSIC방법보다 분해능이 우수함을 입증하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권3호
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• pp.1123-1140
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• 2019

Many Internet of Things (IoT) applications involving bursty traffic have emerged recently with event detection. A power management scheme qualified for uplink bursty traffic (PM-UBT) is proposed by distinguishing between bursty and general uplink traffic patterns in the IEEE 802.11 standard to balance energy consumption and uplink latency, especially for stations with limited power and constrained buffer size. The proposed PM-UBT allows a station to transmit an uplink bursty frame immediately regardless of the state. Only when the sleep timer expires can the station send uplink general traffic and receive all downlink frames from the access point. The optimization problem (OP) for PM-UBT is power consumption minimization under a constrained buffer size at the station. This OP can be solved effectively by the bisection method, which demonstrates a performance similar to that of exhaustive search but with less computational complexity. Simulation results show that when the frame arrival rate in a station is between 5 and 100 frame/second, PM-UBT can save approximately 5 mW to 30 mW of power compared with an existing power management scheme. Therefore, the proposed power management strategy can be used efficiently for delay-intolerant uplink traffic in event-driven IoT applications, such as health status monitoring and environmental surveillance.

• Journal of Communications and Networks
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• 제11권4호
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• pp.390-405
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• 2009

Wireless sensor networks (WSNs) are envisioned to facilitate information gathering for various applications and depending on the application types they may require certain quality of service (QoS) guarantee for successful and guaranteed event perception. Therefore, QoS in WSNs is an important issue and two most important parameters that hinder the goal of guaranteed event perception are time-sensitive and reliable delivery of gathered information, while a minimum energy consumption is desired. In this paper, we propose an energy-aware, multi-constrained and multipath QoS provisioning mechanism for WSNs based on optimization approach. Hence, a detailed analytical analysis of reliability, delay and energy consumption is presented to formulate the optimization problem in an analytical way. A greedy algorithm is proposed to achieve the desired QoS guarantee while keeping the energy consumption minimum. Also, a simple but efficient retransmission mechanism is proposed to enhance the reliability further, while keeping the delay within delay bound. Simulation results demonstrate the effectiveness of our scheme.

• 한국정보통신학회논문지
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• 제11권9호
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• pp.1799-1805
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• 2007

무선 Ad-hoc 네트워크에서의 배터리 고갈에 의해 발생하는 노드 실패는 네트워크 전체의 성능에도 큰 영향을 미치므로 에너지소비를 고려한 라우팅 알고리즘은 매우 중요하다. 본 논문에는 전송 시 노드에 의한 에너지 소비뿐만 아니라 노드의 잔여 에너지와 경로 재설정 시 소요되는 지연까지도 고려한 라우팅 (DEAR; Delay and Energy-Aware Routing) 알고리즘을 제안하였다. 성능분석 결과 DEAR알고리즘은 충분한 잔여 에너지를 보유한 노드로 경로를 설정함으로써 에너지 비율에 따라 균형 있게 에너지를 소비할 수 있었다.

• Journal of Communications and Networks
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• 제16권5호
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• pp.548-558
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• 2014

Load distribution is vital to the performance of multipath transport. The task becomes more challenging in real-time multimedia applications (RTMA), which impose stringent delay requirements. Two key issues to be addressed are: 1) How to minimize end-to-end delay and 2) how to alleviate packet reordering that incurs additional recovery time at the receiver. In this paper, we propose sub-packet based multipath load distribution (SPMLD), a new model that splits traffic at the granularity of sub-packet. Our SPMLD model aims to minimize total packet delay by effectively aggregating multiple parallel paths as a single virtual path. First, we formulate the packet splitting over multiple paths as a constrained optimization problem and derive its solution based on progressive approximation method. Second, in the solution, we analyze queuing delay by introducing D/M/1 model and obtain the expression of dynamic packet splitting ratio for each path. Third, in order to describe SPMLD's scheduling policy, we propose two distributed algorithms respectively implemented in the source and destination nodes. We evaluate the performance of SPMLD through extensive simulations in QualNet using real-time H.264 video streaming. Experimental results demonstrate that: SPMLD outperforms previous flow and packet based load distribution models in terms of video peak signal-to-noise ratio, total packet delay, end-to-end delay, and risk of packet reordering. Besides, SPMLD's extra overhead is tiny compared to the input video streaming.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1911-1916
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• 2003

Parameter set of an LPV system is divided into a number of subsets so that robust feedback gains may be designed for each subset of parameters. A concept of quasi-invariant set is introduced, which allows finite steps of delay in reentrance to the set. A feasible and positively invariant set with respect to a gain-scheduled state feedback control can be easily obtained from the quasi-invariant set. A receding horizon control strategy can be derived based on this feasible and invariant set.