A simulation model for video traffic performance via ATM over TCP/IP

Although TCP has emerged as the standard in data communication, the introduction of ATM technology has raised numerous problems regarding the effectiveness of using TCP over A TM networks, especially when video traffic performance is considered. This paper presents a simulation model for transmission performance of video traffic via ATM over TCP/IP. The interactivity between TCP/IP and ATM, generation of MPEG traffic and evaluation of traffic performance are implemented in the model. The design and implementation details of the model are carefully described. The experiments conducted using the model and experimental results are briefly introduced, revealing the capability of our model in simulating network events and in evaluating potential solutions to performance issues.

MPEG Traffic Performance via TCP over ATM

A large volume of TCP/IP traffic is currently, and in the future will be, carried over ATM networks. A major part of the traffic, which is produced by multimedia sources, is encoded using the MPEG standard. For the performance analysis of transferring MPEG video sequence via TCP/IP over A TM networks, there is a need for appropriate simulation models. This paper describes one such simulation model that we have constructed. A sct of preliminary simulation experiments have been conducted with the mode to assess the impact of different network configurations on the MPEG traffic transmission performance. Our simulation model is able to simulate many of the potential performance issues regarding video traffic via TCPIIP and A TM and can be used to evaluate any potential solutions.

A performance comparison of three wireless multi hop ad-hoc network routing protocols when streaming MPEG4 traffic

Mobile ad-hoc networks are characterised by constant topology changes, the absence of fixed infrastructure and lack of any centralised control. Traditional routing algorithms prove to be inefficient in such a changing environment. Ad-hoc routing protocols such as dynamic source routing (DSR), ad-hoc on-demand distance vector routing (AODV) and destination-sequence distance vector (DSDV) have been proposed to solve the multi hop routing problem in ad-hoc networks. Performance studies of these routing protocols have assumed constant bit rate (CBR) traffic. Real-time multimedia traffic generated by video-on demand and teleconferencing services are mostly variable bit rate (VBR) traffic. Most of these multimedia traffic is encoded using the MPEG standard. (ISO moving picture expert group). When video traffic is transferred over MANETs a series of performance issues arise. In this paper we present a performance comparison of three ad-hoc routing protocols - DSR, AODV and DSDV when streaming MPEG4 traffic. Simulation studies show that DSDV performs better than AODV and DSR. However all three protocols fail to provide good performance in large, highly mobile network environments. Further study is required to improve the performance of these protocols in mobile ad-hoc networks offering VBR services.

A flow control methodology for the rapid generation of vehicle traffic models

This paper presents a conveyor-based methodology to model complex vehicle flows common to factory and distribution warehouse facilities. The AGV and human path modelling techniques available in many commercial discrete event simulation packages require extensive knowledge and time to implement even the simplest flow control rules for multiple vehicle interaction. Although discrete event simulation is accepted as an effective tool to model vehicle delivery movements, human paths and delivery schedules for modern assembly lines, the time to generate accurate models is a significant limitation of existing simulation-based optimisation methodologies. The flow control method has been successfully implemented using two commercial simulation packages. It provides a realistic visual representation, as well as accurate statistical results, and reduces the model development process cost.

Self-adaptive clock synchronisation based on clock precision difference

This paper presents an innovative strategy to synchronize all virtual clocks in asynchronous Internet environments. Our model is based on the architecture of one reference clock and many slave clocks communicating with each other over the Internet. The paper makes three major contributions to this research area. Firstly, one-way information transmission is applied to reduce traffic overhead on the Internet for the purpose of clock synchronization. Secondly, the slave nodes use local virtual time and the arrival timestamp, from the reference node, to create linear mathematical trend models and to retrieve the clock precision differences between reference clock and slave clocks. Finally, a fault-tolerant and self-adaptive model executed by each slave node based on the above linear trend model is created in order to ensure that the virtual clock is running normally, even when the link between the reference node and this slave node has crashed. We also present detailed simulations of this strategy and mathematical analysis on real Internet environments.

Traffic safety education and health promoting school : a metropolitan and rural pilot study

Traffic Safety Education (TSE) is an important part of a school's program; however, it competes with many other components of schooling such as literacy, numeracy and a number of health areas. Hence TSE provision in Victorian schools has been somewhat fragmented and haphazard in its delivery. This small pilot study involved two metropolitan and two rural schools which attempted to link TSE into mainstream school activities through the new Victorian Essential Learning Standards (VELS) utilising the internationally accepted Health Promoting Schools (HPS) framework.
The findings of the pilot study showed that though schools face many demands, understanding and ownership of TSE is possible when administrative support, professional development and adequate planning time are made available. The report outlines several key recommendations to improve the delivery of Traffic Safety Education in Victorian schools.

The design and implementation of a traffic accident analysis system

We designed and implemented a traffic accident analysis system (TAAS) in the paper. TAAS is the system faced traffic accident analysis, which uses the traffic rules (law) as knowledge sources to judge if the driver is responsible for a traffic accident. TAAS has characteristics of separating knowledge base and inference engine, using production rule and backward chaining. Besides, TAAS used predefined text and tracing program to realize explanation mechanism.

Traffic fatalities: does income inequity create an externality?

Responsible for 20 million severe injuries and/or deaths annually, few epidemics receive less attention than traffic accidents. Going beyond confirming an inverted U-shaped relationship between mean income and fatalities, we show theoretically that income inequality can positively affect fatalities in two ways. Each operates through heterogeneity between road users, and while the direct effect can be expected to evaporate with rising income, the indirect effect may prove to be an externality in that the relationship remains regardless of the level of income. Our model is supported by evidence from 79 countries between 1970 and 2000.

Impact of front-of-pack 'traffic-light' nutrition labelling on consumer food purchases in the UK

Front-of-pack ‘traffic-light’ nutrition labelling has been widely proposed as a tool to improve public health nutrition. This study examined changes to consumer food purchases after the introduction of traffic-light labels with the aim of assessing the impact of the labels on the ‘healthiness’ of foods purchased. The study examined sales data from a major UK retailer in 2007. We analysed products in two categories (‘ready meals’ and sandwiches), investigating the percentage change in sales 4 weeks before and after traffic-light labels were introduced, and taking into account seasonality, product promotions and product life-cycle. We investigated whether changes in sales were related to the healthiness of products. All products that were not new and not on promotion immediately before or after the introduction of traffic-light labels were selected for the analysis (n = 6 for ready meals and n = 12 for sandwiches). For the selected ready-meals, sales increased (by 2.4% of category sales) in the 4 weeks after the introduction of traffic-light labels, whereas sales of the selected sandwiches did not change significantly. Critically, there was no association between changes in product sales and the healthiness of the products. This short-term study based on a small number of ready meals and sandwiches found that the introduction of a system of four traffic-light labels had no discernable effect on the relative healthiness of consumer purchases. Further research on the influence of nutrition signposting will be needed before this labelling format can be considered a promising public health intervention.