Minimum Window Size Research Articles

TCP 플로우 간의 공정성 개선을 위한 새로운 큐잉 알고리즘

TCP Vegas 버전은 현재 인터넷에서 가장 많이 사용되고 있는 TCP Tahoe나 Reno 버전에 비하여 높은 성능과 안정된 서비스를 제공한다. 그러나 TCP vegas는 다른 버전의 TCP와 병목 링크를 공유하여 사용하게 되면 TCP Tahoe나 Reno 버전에 비하여 상대적으로 낮은 성능을 나타낸다. 이는 각 버전의 TCP가 수행하는 혼잡제어 알고리즘의 차이에서 기인하는 것으로 이를 해결하기 위한 많은 연구가 진행되고 있다. 본 논문에서는 링크의 대역폭에 따른 TCP의 최대 성능을 유지할 수 있는 최소한의 윈도우 크기를 분석하고 중간 라우터의 큐에서 각 TCP 연결에 적절한 윈도우 크기를 할당하기 위한 패킷 폐기 정책을 수행함으로써 TCP의 성능을 유지하면서 공정성을 개선할 수 있는 알고리즘을 제안한다. 제안한 알고리즘의 성능평가는 각 TCP 연결에 의하여 종단 시스템간에 전송된 데이터 바이트 수를 기준으로 측정하였으며, 그 결과 제안한 알고리즘은 높은 TCP 성능을 유지하면서 공정성이 개선됨을 확인하였다. TCP Vegas version provides better performance and more stable services than TCP Tahoe and Reno versions, which are widely used in the current Internet. However, in the situation where TCP Vegas and Reno share the bottleneck link, the performance of TCP Vegas is much smaller than that of TCP Reno. This unfairness is due to the difference of congestion control mechanisms of each TCP use. Several studies have been executed in order to solve this unfairness problem. In this paper, we analyze the minimum window size to maintain the maximum TCP performance of link bandwidth. In addition, we propose an algorithm which maintains the TCP performance and improves fairness by selective packet drops in order to allocate proper window size of each TCP connections. To evaluate the performance of the proposed algorithm, we have measured the number of data bytes transmitted between end-to-end systems by each TCP connections. The simulation results show that the proposed algorithm maintains the maximum TCP performance and improves the fairness.

Effects of window size and load on estimated myoelectric signal power spectrum

The main objective of this study was to investigate the effects of window size on estimated surface myoelectric signal (MES) parameters in frequency domain. Seven healthy male subjects participated in this study. All subjects were required to perform a sustained isometric muscle contraction corresponding to 25, 50 and 100% of the Maximum Voluntary Contraction (MVC). MES was recorded by surface electrodes for a period of 6 s. Seven different window sizes (64, 128, 256, 512, 1024, 2048, and 4096 ms) were used to estimate the power spectrum. The results obtained showed that the window size has a significant effect on the estimated characteristic frequencies of the power spectrum. The minimum window size that can be used to estimate the power spectrum was found to be 0.5 seconds. The loading level was found to have a significant effect on the frequency domain characteristics. It was observed that the frequencies below the 75th fractile tend to shift upward as the load increases. The upward shift in higher frequencies (≥ 75th fractile) was reversed as the load reached MVC, which indicates that during a constant isometric contraction the shape of the spectrum changes as the force level is increased. The results obtained in this study show that the use of a single spectral variable such as the median frequency may not be sufficient for capturing all the spectral modifications of the MES.

A capacity analysis for the IEEE 802.11 MAC protocol

The IEEE 802.11 MAC protocol provides shared access to a wireless channel. This paper uses an analytic model to study the channel capacity - i.e., maximum throughput - when using the basic access (two-way handshaking) method in this protocol. It provides closed-form approximations for the probability of collision p, the maximum throughput S and the limit on the number of stations in a wireless cell. The analysis also shows that: p does not depend on the packet length, the latency in crossing the MAC and physical layers, the acknowledgment timeout, the interframe spaces and the slot size; p and S (and other performance measures) depend on the minimum window size W and the number of stations n only through a gap g D W=.n 1/ - consequently, halving W is like doubling n ;t he maximum contention window size has minimal effect onp and S; the choice of W that maximizes S is proportional to the square root of the packet length; S is maximum when transmission rate (including collisions) equals the reciprocal of transmission time, and this happens when channel wastage due to collisions balances idle bandwidth caused by backoffs. The results suggest guidelines on when and howW can be adjusted to suit measured traffic, thus making the protocol adaptive.

Seismic data compression by an adaptive local cosine/sine transform and its effects on migration

The local cosine/sine basis is a localized version of the cosine/sine basis with a window function which can have arbitrary smoothness. It has orthogonality and good time and frequency localization properties. The adaptive local cosine/sine basis is a best‐basis obtained from an overabundant library of cosine/sine packets based on a cost‐functional. We propose a 2D semi‐adaptive (time‐adaptive or space‐adaptive) local cosine transform (referred to as a 2D semi‐ALCT) and apply it to the SEG–EAEG salt model synthetic data set for compression. From the numerical results, we see that most of the important features of the data set can be well preserved even in the high compression ratio (CR=40:1) case. Using reconstructed data from the highly compressed ALCT coefficients (CR=40:1) for migration, we can still obtain a high‐quality image including subsalt structures. Furthermore, we find that the window partition, generated by the 2D semi‐ALCT, is well adapted to the characteristics of the seismic data set, and the compression capability of the 2D semi‐ALCT is greater than that of the 2D uniform local cosine transform (2D ULCT). We find also that a (32, 32) or (32, 64) minimum (time, space) window size can generate the best compression results for the SEG–EAEG salt data set.

Optimizing the window size for multiple least squares fitting of electron energy loss spectra

The purpose of this study was to determine the effect of the fitting window size used with the linear least squares fit method when quantitating trace elements with electron energy loss spectroscopy. Theory and computer simulation with a simple model of two 'signals' show that, when the background underlying the signal is slowly varying and the signal is localized, there exists a minimum window optimal for fitting raw spectra. The width of the minimum fitting window can be determined directly from the reference standard spectrum of the signal alone and the estimates of signal and background are related. Use of narrower than the minimum window will increase the fitting uncertainty of the signal and yield less reliable results. More complicated experimental spectra must be fitted to more than two standards and a simple analytical expression of the minimum fitting window cannot be derived, but can be determined empirically. Our study shows that the empirical value obtained from experimental spectra is only slightly larger than the theoretical value derived from the simple model, indicating that this conclusion is still valid. When fitting difference spectra with a slowly varying background, the estimates of signal and background are independent and windows wider than the size of the signal will yield the same fitting uncertainty. In the presence of a non-slowly varying background, common in difference spectra, the minimum window size depends on the fine structure of the signal and the background.

Flame surface density and burning rate in premixed turbulent flames

The flame surface density has been measured in hydrocarbon/air stagnation point and v-shaped premixed turbulent flames. A method is proposed to determine the flame surface density from the data obtained by laser sheet tomography. The average flame length and flame zone area as a function of the progress variable are calculated from a map of progress variable and a set of flame edges obtained from the tomographs. From these results a surface density estimate in two dimensions is determined. By this technique it is possible to avoid the difficulties which arise when using an algebraic model based on the measurement of the flame front geometry and a scalar length scale. From these results the burning rate can be obtained which compares well with estimates calculated using the fractal technique. The present method, however, is not constrained by a minimum window size as is the case for the fractal determinations.

Requirements for the daylighting of dwellings and work places - Standardization based on research

A German Standard “DIN 5034” on daylighting was first published in 1935 and revised in 1959 and 1969. Changing ideas about the meaning of daylight in interiors and the development of new economical artificial light sources led to the necessity to work out a completely new standard. Before this could be accomplished, questions had to be answered, such as how to describe “sufficient daylight” in technical terms and how minimum window dimensions should measure in order to secure the necessary view out. Scale-model research and field studies in Berlin produced results concerning daylight factor, daylight level, window dimension, and sunshine-hour requirements for dwellings. Based partly on these findings, a new standard on daylighting is divided into the following parts: • General Requirements • Basis • Calculation • Simplified Determination of Minimum Window Sizes for Dwellings • Measurement.

Critical minimum acceptable window size: a study of window design and provision of a view : Ne'eman, E. and Hopkinson, R.G.Lighting Research and Technology, 1970, 2.1, 17–27; abstr. in Building Science Abstracts

Critical minimum acceptable window size: a study of window design and provision of a view : Ne'eman, E. and Hopkinson, R.G.Lighting Research and Technology, 1970, 2.1, 17–27; abstr. in Building Science Abstracts

Critical minimum acceptable window size: a study of window design and provision of a view : Ne'eman, E. and Hopkinson, R. G.Lighting Research and Technology, 1970,2.17–27

Critical minimum acceptable window size: a study of window design and provision of a view : Ne'eman, E. and Hopkinson, R. G.Lighting Research and Technology, 1970,2.17–27

Critical minimum acceptable window size: a study of window design and provision of a view

When working light is provided by permanent supplementary artificial lighting, the function of the window is modified. The main visual functions then become (a) the provision of a view, and (b) the provision of some modelling light to enhance the appearance of solid objects. This study was concerned to establish whether a critical minimum size of window could be assessed subjectively. It was found that a criterion could be recognised, and that this critical minimum size was governed more by the visual information provided by the view outside than by the amount of daylight or sunlight which penetrates the room, by the level of interior artificial lighting or by the viewing position in the room.