• Title/Summary/Keyword: frame delay

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A Hexagon Model-based Efficient Beacon Scheduling Approach for Wireless Sensor Networks

  • Lee, Taekkyeun
    • Journal of the Korea Society of Computer and Information
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    • v.23 no.9
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    • pp.43-50
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    • 2018
  • In this paper, we propose a hexagon model-based efficient beacon frame scheduling approach for wireless sensor networks. The existing beacon frame scheduling approaches use a lot of slots and subslots for the beacon frame scheduling. Thus, the data from source nodes are not efficiently delivered to a sink node. Also in case a sink node needs to broadcast a beacon frame to the nodes in the network, delivering the beacon frame to the network nodes is not efficient as well. Thus, to solve the problem, we use a hexagon model to find the number of slots and subslots for the beacon frame scheduling. By using them for the beacon frame scheduling, the proposed approach performs better than other approaches in terms of the data transmission delay, the number of received data, the beacon transmission delay and the number of relaying the beacon frames.

A Buffer Management Algorithm based on the GOP Pattern and the Importance of each Frame to Provide QoS for Streaming Services in WLAN (WLAN에서 스트리밍 서비스이 QoS를 제공하기 위한 GOP 패턴 및 프레임 중요도에 따른 버퍼 관리 기술)

  • Kim, Jae-Hyun;Lee, Hyun-Jin;Lee, Kyu-Hwan;Roh, Byeong-Hee
    • 한국정보통신설비학회:학술대회논문집
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    • 2008.08a
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    • pp.372-375
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    • 2008
  • IEEE 802.11e standardized the EDCA mechanism to support the priority based QoS. And the virtual collision handler schedules the transmission time of each MAC frame using the internal back-off window according to the access category(AC). This can provides the differentiated QoS to real-time services at the medium traffic load condition. However, the transmission delay of MAC frame for real-time services may be increased as the traffic load of best effort service increases. It becomes more critical when the real-time service uses a compressed mode video codec such as moving picture experts group(MPEG) 4 codec. That is because each frame has the different importance. That is, the I-frame has more information as compared with the P- and the B-frame. In this paper, we proposed a buffer management algorithm based on the frame importance and the delay bound. The proposed algorithm is consisted of the traffic regulator based on the dual token bucket algorithm and the active queue management algorithm. The traffic regulator reduces the transmission rate of lower AC until that the virtual collision handler can transmit an I-frame. And the active queue management discards frame based on the importance of each frame and the delay bound of head of line(HoL) frame when the channel resource is insufficient.

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Performance Analysis of Wireless Communication Networks for Smart Metering Implemented with Channel Coding Adopted Multi-Purpose Wireless Communication Chip (오류 정정 부호를 사용하는 범용 무선 통신 칩으로 구현된 스마트 미터링 무선 네트워크 시스템 성능 분석)

  • Wang, Hanho
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.64 no.4
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    • pp.321-326
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    • 2015
  • Smart metering is one of the most implementable internet-of-thing service. In order to implement the smart metering, a wireless communication network should be newly designed and evaluated so as to satisfy quality-of-service of smart metering. In this paper, we consider a wireless network for the smart metering implemented with multi-purpose wireless chips and channel coding-functioned micro controllers. Especially, channel coding is newly adopted to improve successful frame transmission probability. Based on the successful frame transmission probability, average transmission delay and delay violation probability are analyzed. Using the analytical results, service coverage expansion is evaluated. Through the delay analysis, service feasibility can be verified. According to our results, channel coding needs not to be utilized to improve the delay performance if the smart metering service coverage is several tens of meters. However, if more coverage is required, chanel coding adoption definitely reduces the delay time and improve the service feasibility.

An Improvement in Synchronously Rotating Reference Frame-Based Voltage Sag Detection under Distorted Grid Voltages

  • Sillapawicharn, Yutthachai;Kumsuwan, Yuttana
    • Journal of Electrical Engineering and Technology
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    • v.8 no.6
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    • pp.1283-1295
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    • 2013
  • This study proposed an improvement in synchronously rotating reference frame-based voltage sag detection under distorted grid voltages. In the past, the conventional synchronously rotating reference frame (CSRRF)-based voltage sag detection was generally used in the voltage sag compensation applications. Its disadvantage is a long delay of detection time. The modified synchronously rotating reference frame (MSRRF)-based voltage sag detection is able to detect the voltage sag with only a short delay in detection time. However, its operation under distorted grid voltage conditions is unavailable. This paper proposed the improvement of modified synchronously rotating reference frame (IMSRRF)-based voltage sag detection for use in distorted grid voltages with very fast operation of voltage sag detection. The operation of the proposed voltage sag detections is investigated via simulations and experimentations to verify the performance of the IMSRRF-based voltage sag detection.

HFIFO(Hierarchical First-In First-Out) : A Delay Reduction Method for Frame-based Packet Transmit Scheduling Algorithm (계층적 FIFO : 프레임 기반 패킷 전송 스케쥴링 기법을 위한 지연 감축 방안)

  • 김휘용;유상조;김성대
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.5C
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    • pp.486-495
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    • 2002
  • In this paper, we propose a delay reduction method for frame-based packet transmit scheduling algorithm. A high-speed network such as ATM network has to provide some performance guarantees such as bandwidth and delay bound. Framing strategy naturally guarantees bandwidth and enables simple rate-control while having the inherently bad delay characteristics. The proposed delay reduction method uses the same hierarchical frame structure as HRR (Hierarchical Round-Robin) but does not use the static priority scheme such as round-robin. Instead, we use a dynamic priority change scheme so that the delay unfairness between wide bandwidth connection and narrow bandwidth connection can be eliminated. That is, we use FIFO (First-In First-Out) concept to effectively reduce the occurrence of worst-case delay and to enhance delay distribution. We compare the performance for the proposed algorithm with that of HRR. The analytic and simulation results show that HFIFO inherits almost all merits of HRR with fairly better delay characteristics.

Audio /Speech Codec Using Variable Delay MDCT/IMDCT (가변 지연 MDCT/IMDCT를 이용한 오디오/음성 코덱)

  • Sangkil Lee;In-Sung Lee
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.16 no.2
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    • pp.69-76
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    • 2023
  • A high-quality audio/voice codec using the MDCT/IMDCT process can perfectly restore the current frame through an overlap-add process with the previous frame. In the overlap-add process, an algorithm delay equal to the frame length occurs. In this paper, we propose a MDCT/IMDCT process that reduces algorithm delay by using a variable phase shift in MDCT/IMDCT process. In this paper, a low-delay audio/speech codec was proposed by applying the low delay MDCT/IMDCT algorithm to the ITU-T standard codec G.729.1 codec. The algorithm delay in the MDCT/IMDCT process can be reduced from 20 ms to 1.25 ms. The performance of the decoded output signal of the audio/speech codec to which low-delay MDCT/IMDCT is applied is evaluated through the PESQ test, which is an objective quality test method. Despite of the reduction in transmission delay, it was confirmed that there is no difference in sound quality from the conventional method.

On the Optimal Cyclic Delay Value in Cyclic Delay Diversity (순환 지연 다이버시티 기법에서의 최적의 순환 지연 값)

  • Kim, Yong-June;Rim, Min-Joong;Jeong, Byung-Jang;Noh, Tae-Gyun;Kim, Ho-Yun;Lim, Dae-Woon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.9C
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    • pp.643-651
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    • 2008
  • In this paper, we propose a method to determine the optimal cyclic delay value of cyclic delay diversity(CDD) in orthogonal frequency division multiplexing(OFDM) systems. As the cyclic delay value increases, we can get signal to interference and noise ratio(SINR) gain by diversity effect, while SINR loss increases because of channel estimation errors. If the optimal delay value obtained by the proposed method is applied to CDD scheme, we can minimize the required SINR for a given FER(frame error rate) under the above mentioned trade-off.

Non-Reference P Frame Coding for Low-Delay Encoding in Internet Video Coding (IVC의 저지연 부호화 모드를 위한 비참조 P 프레임의 부호화 기법)

  • Kim, Dong-Hyun;Kim, Jin-Soo;Kim, Jae-Gon
    • Journal of Broadcast Engineering
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    • v.19 no.2
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    • pp.250-256
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    • 2014
  • Non-reference P frame coding is used to enhance coding efficiency in low-delay encoding configuration of Internet Video Coding (IVC), which is being standardized as a royalty-free video codec in MPEG. The existing method of non-reference P frame coding which was adopted in the reference Test Model of IVC (ITM) 4.0 adaptively applies a non-reference P frame with a fixed coding structure based on the magnitude of motion vectors (MVs), however, which unexpectedly degrades the coding efficiency for some sequences. In this paper, the existing non-reference P frame coding is improved by changing non-reference P frame coding structure and applying a new adaptive method using the ratio of the amount of generated bits of non-reference frames to that of reference frames as well as MVs. Experimental results show that the proposed non-reference P frame coding gives 6.6% BD-rate bit saving in average over ITM 7.0.

LONG-TERM VARIATION OF THE SHUTTER DELAY TIME OF Y4KCAM OF THE CTIO 1.0 M TELESCOPE

  • Lee, Jae-Woo;Pogge, Richard
    • Journal of The Korean Astronomical Society
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    • v.49 no.6
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    • pp.289-293
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    • 2016
  • We investigate the long-term spatial drift of the center and the temporal variation of the shutter delay time map of Y4KCam mounted on the CTIO 1.0 m telescope. We have collected shutter delay time maps over eight years as a part of our long-term survey program. We find that the center of the shutter delay time map can drift up to $450{\mu}m$, equivalent to ${\approx}30pixels$, on the CCD. This effect can result in a small amount of error in integration time without the proper shutter delay time correction, but it does not appear to cause any significant problems in photometric measurements. We obtain a mean shutter delay time of $69.1{\pm}0.8$ ms and find no temporal variation of the shutter delay time of Y4KCam over eight years, indicative of the mechanical stability of the shutter. We suggest that using a master shutter delay time correction frame would be sufficient to achieve high precision photometry, which does not exceed photometric errors ${\approx}1.7mmag$ across the CCD frame for exposure times longer than 1 s.

A Study on the Improvement of Real-Time Traffic QoS using the Delay Guarantee Queue Service Discipline of End-to-End (종단간 지연 큐 서비스 방식을 이용한 실시간 트래픽 QoS 개선에 관한 연구)

  • 김광준;나상동
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.6 no.2
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    • pp.236-247
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    • 2002
  • We propose a cell-multiplexing scheme for the real-time communication service in ATM network and a new service discipline guarantee end-to-end delay based on pseudo-isochronous cell switching. The proposed scheme consists of two level frame hierarchy, upper and lower frame, which is used to assign the bandwidth and to guarantee the requested delay bound, respectively. Since the Proposed algorithm employs two level frame hierarchy, it can overcome the coupling problem which is inherent to the framing strategy It can be comparatively reduce the complexity, and still guarantee the diverse delay bounds of end-to-end. Besides, it consists of two components, traffic controller and scheduller, as the imput traffic description model and regulates the input traffic specification. The function of the traffic controller is to shape real -time traffic to have the same input pattern at every switch along the path. The end-to-end delay is bounded by the scheduller which can limit the delay variation without using per-session jitter controllers, and therefore it can decrease the required buffer size. The proposed algorithm can support the QoS's of non-real time traffic as well as those of real time traffic.