To ensure customer satisfaction and greater market acceptance, voice over Wi-Fi networks must ensure voice quality under various network parameters, configurations and traffic conditions, and other practical effects, e.g., channel noise, and capturing effects. An accurate voice capacity estimation model considering these factors can greatly assist network designers. In the current work, we propose an analytical model to estimate voice over Internet Protocol (VoIP) capacity over Wi-Fi networks addressing these issues. We employ widely used ITU-T E-model to assess voice quality and VoIP call capacity is presented in the form of an optimization problem with voice quality requirement as a constraint. In particular, we analyze delay and loss in channel access and queue, and their impacts on voice quality. The proposed capacity model is first developed for a single hop wireless local area network (WLAN) and then extended for multihop scenarios. To model real network scenario closely, we also consider channel noise and capture effect, and analyze the impacts of transmission range, interference range, and WLAN radius. In absence of any existing call capacity model that considers all the above factors concomitantly, our proposed model will be extremely useful to network designers and voice capacity planners.
Timber poles are widely used for distributing electricity in rural areas, mainly in developing countries. The improved reliability of timber poles is extremely important as the breakdown or failure of any one of these poles can result in millions of dollars in lost revenue and restoration costs. The losses can include production loss, loss of property, or even loss of life. The reliability of such poles depends on a complex combination of age, usage, durability of timber, environmental factors influencing the deterioration process, and most important, maintenance actions carried out through the lifecycle of the poles. This paper focuses on developing an optimal maintenance model that predominantly captures the inground decay of timber poles, and on developing a mechanism for measuring these factors. The developed maintenance model is then illustrated with numerical examples. Analysis of failure data shows that most of the failures of timber poles are due to a decrease in timber strength and peripheral dimensions at or below ground level. The results from this research could be useful for maintenance and replacement decisions regarding inground timber components used in the utility, construction, railway, and transportation sectors.