User-perceived quality of service in wireless data networks

For so long, the term quality of service (QoS) has been a pursuit area for network engineers trying to dimension wireless networks to run in the most efficient way possible. Of late, there has been a trend reversal, looking at the user perceptions of the network performance to decide where dimensioning can have the greatest impact. This paper demonstrates the importance of defining the concept of user-perceived QoS and linking this to specific wireless data network parameters for some anticipated valuable applications. It has been shown that a quantitative rating can be obtained for a variety of important factors in the assessment of service quality, and mapped to specific values of multiple network parameters. We found QoS to be application-specific, where various applications require different levels of network performance to satisfy users. The role of physical location was also examined, investigating the influence of being indoors versus outdoors on the user perception of QoS.     

A survey of MAC based QoS implementations for WiMAX networks

We present a comprehensive survey of proposed Quality of Service (QoS) mechanisms in the Media Access Control (MAC) sublayer of WiMAX based wireless networks. QoS support in WiMAX is a fundamental design requirement, and is considerably more difficult than in wired networks, mainly because of the variable and unpredictable characteristics of wireless links.We discuss various QoS architectures, signaling mechanisms and admission control techniques proposed in the WiMAX research literature, summarizing the operation of each, and providing comparative evaluations that include advantages and limitations.     

A deadlock model for a multi‐service medium access protocol employing multi‐slot N‐ary stack algorithm (msSTART)

Many modern multi‐service medium access protocols (MACs) use a collision based capacity request signaling channel as part of a hybrid TDMA frame structure. Multi‐slot Stack Random Access Algorithm (msSTART) is proposed for use in IEEE 802.14 hybrid fiber/coaxial network and will be highly relevant for the S‐MAC development of evolving WATM MAC specifications. This paper studies the performance of msSTART as an example of a Q‐ary tree contention resolution algorithm (CRA) in the wireless environment using the novel Basic Deadlock model. We contrast approximate results for msSTART performance obtained by simulation under extreme inter‐station correlation with analytical results for the more popular p‐persistence CRA used in several testbed WATM implementations. Using three signaling channel schemes designed to provide support for increased system stability, to implement priority in the wireless MAC, and maximise efficiency, we provide comparative results for evaluation of msSTART and p‐persistence ALOHA under what the IEEE 802.14 working group has termed the “disaster scenario”. We find that of the three schemes evaluated the full Contention Mini‐Slot (CMS) sharing scheme employing multiple CMSs per data region extends the protocol's useable load region the furthest. We conclude that Q‐ary tree contention resolution algorithms (in particular msSTART) are best adapted to the wireless environment, providing less case sensitive performance. This revised version was published online in July 2006 with corrections to the Cover Date.     

NFPA's perspectives on performance-based codes and standards

Our ability to predict fire behavior and its effects on our lives has greatly improved over the past quarter century. Numerous scientific advancements have introduced new approaches and tools for the fire safety-related design of both the built environment and the development of new products. However, many of these new methods are not currently used on a routine basis.A growing number of individuals in the fire safety community think that our current fire safety design and approval process, coupled with the rigid make-up of our existing codes and standards, inhibit the greater application of these new methods. While many factors such as resistance to change and the potential misapplication of calculation tools, can account for this inhibiting effect, this paper focuses on the role of codes and standards and discusses how they might better serve the transfer and application of new technology.