Analysis of Aggregated HTTP-based Video Traffic

Biernacki, Arkadiusz The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.5

Increase of hypertext transfer protocol (HTTP)-based video popularity causes that broadband and Internet service providers' links transmit mainly multimedia content. Network planning, traffic engineering or congestion control requires understanding of the statistical properties of network traffic; therefore, it is desirable to investigate the characteristic of traffic traces generated, among others, by systems which employ adaptive bit-rate streaming. In our work, we investigate traffic originating from 120 client-server pairs, situated in an emulated laboratory environment, and multiplexed onto a single network link. We show that the structure of the traffic is distinct from the structure generated by first and second generation of HTTP video systems, and furthermore, not similar to the structure of general Internet traffic. The obtained traffic exhibits negative correlations, anti-persistence, and its distribution function is skewed to the right. Furthermore, we show that the traffic generated by clients employing the same or similar play-out strategies is positively correlated and synchronised (clustered), whereas traffic originated from different play-out strategies shows negative or no correlations.

Analysis of Aggregated HTTP-based Video Traffic

Arkadiusz Biernacki 한국통신학회 2016 Journal of communications and networks Vol.18 No.5

Increase of hypertext transfer protocol (HTTP)-basedvideo popularity causes that broadband and Internet serviceproviders’ links transmit mainly multimedia content. Networkplanning, traffic engineering or congestion control requires un-derstanding of the statistical properties of network traffic; there-fore, it is desirable to investigate the characteristic of traffic tracesgenerated, among others, by systems which employ adaptive bit-rate streaming. In our work, we investigate traffic originating from120 client-server pairs, situated in an emulated laboratory environ-ment, andmultiplexed onto a single network link.We show that thestructure of the traffic is distinct from the structure generated byfirst and second generation of HTTP video systems, and further-more, not similar to the structure of general Internet traffic. Theobtained traffic exhibits negative correlations, anti-persistence,and its distribution function is skewed to the right. Furthermore,we show that the traffic generated by clients employing the sameor similar play-out strategies is positively correlated and synchro-nised (clustered), whereas traffic originated from different play-outstrategies shows negative or no correlations.

Analysis of the Material and Design Modifications Influence on Strength of the Cycloidal Gear System

Krzysztof Biernacki 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

The working unit of the hydraulic gerotor machine is a system of cycloidal gears. In the paper, ways of increasing the load-carryingcapacity of the plastic cycloidal gears have been presented. The objective has been achieved through of structural and materialmodifications. The modifications were introduced while making the numerical models of the cycloidal gear system. The fundamentalfeature of the modifications is the combination of a plastic and a steel core in the design of the cycloidal gear system. While examiningthe system, the influence of the plastic-steel combination on the stress and deformation distributions in the operation of the cycloidalgears was verified. The numerical analysis was conducted using the finite elements method. The results of the analysis show that theintroduction of the modifications strengthens the cycloidal gear system. Therefore, the conclusion that a system can work in the fluidpower gerotor machines dedicated to operating at higher working pressure p seems justified. A result of the analysis is a presentationof solutions which will enable the strengthening and a higher load-carrying capacity of the gear system. Another finding of theresearch was determination of the maximum value of working pressure p at which the hydraulic gerotor machines with the modifiedcycloidal gears can operate.

Server Side Solutions For Web-Based Video

( Arkadiusz Biernacki ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.4

In contemporary video streaming systems based on HTTP protocol, video players at the client side are responsible for adjusting video quality to network conditions and user expectations. However, when multiple video clips are streamed simultaneously, an intricate application logic implemented in the video players overlays the TCP mechanism which is responsible for a balanced access to a shared network link. As a result, some video players may not obtain a fair share of network throughput and may be vulnerable to an unstable video bit-rate. Therefore, we propose to simplify the algorithms implemented in the video players, which are responsible for the adjustment of video quality and constrain their functionality only to sending feedback to a server about a state of the player buffer. The main logic of the system is shifted to the server, which is now responsible for bit-rate selection and prioritisation of the video streams transmitted to multiple clients. To verify our proposition, we performed several experiments in a laboratory environment which show that when the server cooperates with the clients, the video players experience fewer quality switches and the system achieves better fairness when allocating network throughput among the video players. However, this comes at the cost of worse utilisation of network bandwidth.

Improving Video Quality by Diversification of Adaptive Streaming Strategies

( A. Biernacki ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.1

Users quite often experience volatile channel conditions which negatively influence multi-media transmission. HTTP adaptive streaming has emerged as a new promising technology where the video quality can be adjusted to variable network conditions. Nevertheless, the new technology does not remain without drawbacks. As it has been observed, multiple video players sharing the same network link have often problems with achieving good efficiency and stability of play-out due to a mutual interference and competition among video players. Our investigation indicates that there may be another cause for under-performance of the streamed video. In an emulated environment, we implemented three algorithms of adaptive video play-out based on bandwidth or buffer assessment. As we show, traffic generated by players employing the same or similar play-out strategies is positively correlated and syn-chronised (clustered), whereas traffic originated from different play-out strategies shows negative or no correlations. However, when some of the parameters of the play-out strategies are randomised, the correlation and synchronisation diminish what has a positive impact on the smoothness of the traffic and on the video quality perceived by end users. Our research shows that non-correlated traffic flows generated by play-out strategies improve efficiency and stability of streamed adaptive video.

Improving Quality of Adaptive Video by Traffic Prediction with (F)ARIMA Models

Arkadiusz Biernacki 한국통신학회 2017 Journal of communications and networks Vol.19 No.5

During the past years, adaptive video based on hypertexttransfer protocol HTTP has become very popular. Streamingof the adaptive video relies heavily on an estimation of end-to-endnetwork throughput, which can be challenging especially in mobilenetworks, where the capacity highly fluctuates. In this work,we propose to predict the network throughput using its past measurements. As the analysis shows, the network throughput forms along range-dependent process, thus, for the throughput predictionwe apply fractional ARIMA (FARIMA) model. Our approach doesnot require any modifications to the network infrastructure or theTCP stack. The predictions are performed for data traces obtainedfrom measurements of throughput of a real mobile network. Asthe experiment shows, the obtained traffic model is able to enhancethe performance of an adaptive streaming algorithm. Compared tothe throughput predictors employed in contemporary systems dedicatedto adaptive video streaming, the proposed technique obtainsbetter results when taking into account effectiveness of network capacityutilisation and stability of video play-out.

An advanced single-particle model for C3S hydration - validating the statistical independence of model parameters

Joseph J. Biernacki,Manohar Gottapu 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.6

An advanced continuum-based multi-physical single particle model was recently introduce for the hydration of tricalcium silicate (C3S). In this model, the dissolution and the precipitation events are modeled as two different yet simultaneous chemical reactions. Product precipitation involves a nucleation and growth mechanism wherein nucleation is assumed to happen only at the surface of the unreacted core and product growth is characterized via a two-step densification mechanism having rapid growth of a low density initial product followed by slow densification. Although this modeling strategy has been shown to nicely mimic all stages of C3S hydration – dissolution, dormancy (induction), the onset of rapid hydration, the transition to slow hydration and prolonged reaction – the major criticism is that many adjustable parameters are required. If formulated correctly, however, the model parameters are shown here to be statistically independent and significant.

The origins and evolution of cement hydration models

Tiantian Xie,Joseph J. Biernacki 사단법인 한국계산역학회 2011 Computers and Concrete, An International Journal Vol.8 No.6

Our ability to predict hydration behavior is becoming increasingly relevant to the concrete community as modelers begin to link material performance to the dynamics of material properties and chemistry. At early ages, the properties of concrete are changing rapidly due to chemical transformations that affect mechanical, thermal and transport responses of the composite. At later ages, the resulting, nano-, micro-, meso- and macroscopic structure generated by hydration will control the life-cycle performance of the material in the field. Ultimately, creep, shrinkage, chemical and physical durability, and all manner of mechanical response are linked to hydration. As a way to enable the modeling community to better understand hydration, a review of hydration models is presented offering insights into their mathematical origins and relationships one-to-the-other. The quest for a universal model begins in the 1920’s and continues to the present, and is marked by a number of critical milestones. Unfortunately, the origins and physical interpretation of many of the most commonly used models have been lost in their overuse and the trail of citations that vaguely lead to the original manuscripts. To help restore some organization, models were sorted into four categories based primarily on their mathematical and theoretical basis: (1) mass continuity-based, (2) nucleation-based, (3) particle ensembles, and (4) complex multiphysical and simulation environments. This review provides a concise catalogue of models and in most cases enough detail to derive their mathematical form. Furthermore, classes of models are unified by linking them to their theoretical origins, thereby making their derivations and physical interpretations more transparent. Models are also used to fit experimental data so that their characteristics and ability to predict hydration calorimetry curves can be compared. A sort of evolutionary tree showing the progression of models is given along with some insights into the nature of future work yet needed to develop the next generation of cement hydration models.