• Title, Summary, Keyword: mean delay

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MEAN SQUARE EXPONENTIAL DISSIPATIVITY OF SINGULARLY PERTURBED STOCHASTIC DELAY DIFFERENTIAL EQUATIONS

  • Xu, Liguang;Ma, Zhixia;Hu, Hongxiao
    • Communications of the Korean Mathematical Society
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    • v.29 no.1
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    • pp.205-212
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    • 2014
  • This paper investigates mean square exponential dissipativity of singularly perturbed stochastic delay differential equations. The L-operator delay differential inequality and stochastic analysis technique are used to establish sufficient conditions ensuring the mean square exponential dissipativity of singularly perturbed stochastic delay differential equations for sufficiently small ${\varepsilon}$ > 0. An example is presented to illustrate the efficiency of the obtained results.

Mean time delay variation performane of DTTL bit synchronizer (DTTL 비트동기장치의 평균시간지연 편차 성능에 관한 연구)

  • 김관옥
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.22 no.11
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    • pp.2401-2408
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    • 1997
  • The measured pulse shapes provided in the given data package demonstrated pulse distortions due to laser speckle. the distorted pulse shapes were carefully analyzed, modeled, and then applied to the DTTL(Digital-data Transition Tracking Loop)[1] bit synchronizer simulator to measure the mean time delay and its delay variation performance. The result showed that the maximum mean time delay variation with the modeled data was 12.5% when window size equals 1. All the data given were located within this modeled boundary and the maximum eman time delay variation was 7% in this case. The mean time delay variation was known to be smaller by reducing the window size [2][5][6]. The mitigated delay variation was 2.5% in the modeled case and 1.4% in the data set given when the windown size equals 0.1. With the digital DTTL insteal of analog DTTL, similar results was obtained.

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Experimenatal analysis of radio propagation delay characteristics in urban microcells (도심 마이크로셀에서의 무선 전파지연 특성에 관한 실험적 분석)

  • 박시우;곽우영;박진우
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.9
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    • pp.2494-2504
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    • 1996
  • This paper describes about the spread specturm radio wave propagation characteristics in urban microcells. The experiments are carried out with respect to the mean excess delay, the RMS delay spread, and the received maximum peak power in the two kinds of geogrphical areas, LOS area and N-LOS area, especially whose variations are observed while varying the transmission distance and tilting the transmitting antenna. The typical results obtained in pariticular urban sites in Seoul are 300-600 nsec of mean excess delay and about 75 nsec of averaged RMS delay spread for LOS area, and 270-280 nsec of mean excess delay and about 100 nsec for N-LOS area. With the transmitting antenna gilted, obsered in the experiments are increase in RMS delay spread as expected, but increase of the received power at N-LOS areas in particular.

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Two Phase Heuristic Algorithm for Mean Delay constrained Capacitated Minimum Spanning Tree Problem (평균 지연 시간과 트래픽 용량이 제한되는 스패닝 트리 문제의 2단계 휴리스틱 알고리즘)

  • Lee, Yong-Jin
    • The KIPS Transactions:PartC
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    • v.10C no.3
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    • pp.367-376
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    • 2003
  • This study deals with the DCMST (Delay constrained Capacitated Minimum Spanning Tree) problem applied in the topological design of local networks or finding several communication paths from root node. While the traditional CMST problem has only the traffic capacity constraint served by a port of root node, the DCMST problem has the additional mean delay constraint of network. The DCMST problem consists of finding a set of spanning trees to link end-nodes to the root node satisfying the traffic requirements at end-nodes and the required mean delay of network. The objective function of problem is to minimize the total link cost. This paper presents two-phased heuristic algorithm, which consists of node exchange, and node shift algorithm based on the trade-off criterions, and mean delay algorithm. Actual computational experience and performance analysis show that the proposed algorithm can produce better solution than the existing algorithm for the CMST problem to consider the mean delay constraint in terms of cost.

Measurement and Analysis of Propagation Characteristics in Curved Subway Tunnel Environments (곡선형 지하철 터널환경에서 전파 특성의 측정과 분석)

  • 정회동;박노준;강영진;송문규
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.8A
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    • pp.950-961
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    • 2004
  • In this paper, we measured and analyzed propagation characteristics in a subway tunnel that is recently increasingly becoming one of the radio communication environments. The measurements are carried out in a subway tunnel with frequency bands of 2.45㎓ and 5.8㎓. The length of tunnel we used for this study is 175m of LOS (Line-of-sight) and 270m of NLOS (Non Line-of-Sight). The subway tunnel is curved and its cross section is horseshoe type. The measurement systems we employ in this study are a narrow-band system and a wide-band system. The narrow-band system is used to get path loss measurement and the wide-band system is used to figure out delay profile measurement. In particular, the wide-band system consists of 1023 length PN sequence generator using a chip rate of 80MHz based on a sliding correlation technique. The omni-directional antennas and directional antennas are used to analyze propagation characteristics for beam type of antenna. The path loss displays only pure path loss of a tunnel environment. The delay profile indicates the mean excess delay and RMS (root mean square) delay spread.

Optimum Uplink Power/Rate Control for Minimum Delay in CDMA Networks

  • Choi, Kwon-Hue;Kim, Soo-Young
    • ETRI Journal
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    • v.25 no.6
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    • pp.437-444
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    • 2003
  • We derive a new joint power and rate control rule with which we can minimize the mean transmission delay in CDMA networks for a given mean transmission power. We show that it is optimal to respectively control the power inverse-linearly and the rate linearly to the square root of channel gain while maintaining the signal-to-interference ratio at a constant. We also show that the proposed joint power/rate control rule achieves excellent performance results in terms of the probability of the instantaneous delay being within a target delay against one-dimensional control schemes.

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Mean Response Delay Estimation for HTTP over SCTP in Wireless Internet (무선 인터넷 환경에서 HTTP over SCTP의 평군 응답 시간 추정)

  • Lee, Yong-Jin
    • The Journal of the Korea Contents Association
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    • v.8 no.6
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    • pp.43-53
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    • 2008
  • Hyper text transfer protocol (HTTP) over transmission control protocol (TCP) is currently used to transfer objects in the Internet. Stream control transmission protocol (SCTP), an alternative to TCP, which allows for independent delivery among streams, and can thus reduce the mean response delay of web object. We present an analytical model to find the mean response delay for HTTP over SCTP, therefore, estimate the effectiveness of SCTP over TCP. Typical TCP delay models assume the wired environment. On the contrary, the proposed model in this paper assumes the multiple packet losses and wireless environment where fast retransmission is not possible due to small window. The estimated mean response time can be used the benchmark to meet quality of service (QoS) at end-user. We validate the accuracy of our model using experiments. It is shown that the differences between the results from model and those from experimental are very small below 6 % on average. We also find that the mean response delay for HTTP over SCTP is less than that for HTTP over TCP.

Deadline-Aware Routing: Quality of Service Enhancement in Cyber-Physical Systems (사이버물리시스템 서비스 품질 향상을 위한 데드라인 인지 라우팅)

  • Son, Sunghwa;Jang, Byeong-Hoon;Park, Kyung-Joon
    • KIPS Transactions on Computer and Communication Systems
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    • v.7 no.9
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    • pp.227-234
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    • 2018
  • Guaranteeing the end-to-end delay deadline is an important issue for quality of service (QoS) of delay sensitive systems, such as real-time system, networked control system (NCS), and cyber-physical system (CPS). Most routing algorithms typically use the mean end-to-end delay as a performance metric and select a routing path that minimizes it to improve average performance. However, minimum mean delay is an insufficient routing metric to reflect the characteristics of the unpredictable wireless channel condition because it only represents average value. In this paper, we proposes a deadline-aware routing algorithm that maximizes the probability of packet arrival within a pre-specified deadline for CPS by considering the delay distribution rather than the mean delay. The proposed routing algorithm constructs the end-to-end delay distribution in a given network topology under the assumption of the single hop delay follows an exponential distribution. The simulation results show that the proposed routing algorithm can enhance QoS and improve networked control performance in CPS by providing a routing path which maximizes the probability of meeting the deadline.

Reasons for Patient's Delay in Diagnosis of Breast Carcinoma in Pakistan

  • Memon, Zahid Ali;Shaikh, Anum Nizamuddin;Rizwan, Sundus;Sardar, Maimoona Batool
    • Asian Pacific Journal of Cancer Prevention
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    • v.14 no.12
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    • pp.7409-7414
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    • 2013
  • Background: Delay in diagnosis of breast cancer is associated with a poorer survival and a pivotal contribution to this delayed diagnosis comes from patient delay in presenting at a clinic. Reasons involved must be evaluated in order to decrease this reducible delay. Objectives: i) To evaluate the reasons for patient delay in diagnosis of breast cancer; ii) to investigate any association with other variables. Materials and Methods: A 6 month cross sectional study (from July 2012 to Dec 2012), was carried out in Surgical and Oncology Units of Civil Hospital, Karachi. A total of 100 females diagnosed with breast cancer of any histological type were interviewed after informed consent and relevant data were collected. Due ethical clearance was obtained. Results: Mean age was $47.5{\pm}12.1$ years with a range from 25-77 years. Mean duration of delay was $5.13{\pm}4.8$ months, from shortest 1 month to longest 36 months. Duration of delay was observed to be no delay (<1 month) in 28%, short delay (1-3 months) in 30% and long delay (>3 months) in 42% of patients. Considering the symptoms as "harmless" (39%) was the most frequent reason of delay followed by "temporary" (20%) and the "use of traditional methods" (12%). Most common reason for later approaches was an increase in the size of the lump (41%). Statistically significant association (p-value <0.05) of longer patient delay was obtained with being single, being illiterate, painless breast lump as the first symptom, negative family history of breast cancer and vague attribution of the symptoms. Conclusions: Significant delay in approach to health care facility was observed in our study due to variable reasons given by women. Sufficient awareness regarding breast cancer, its symptoms and favorable effects of a timely diagnosis on prognosis must be imparted to our general population.