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  • Impacts of GPS-based synchronization degradation of cellular networks
    (2007) Khan, Faisal; Dempster, Andrew
    Conference Paper
    GPS timing receivers have long been relied upon by various communications networks for achieving synchronization among the network nodes. Cellular networks, particularly CDMA cellular networks, actively employ GPS timing receivers for making their time critical decisions, particularly handoff. Operations and parameters which set the network quality of service (QoS) require that these GPS receivers provide timing solution up to nano-second accuracy. Therefore, GPS timing receiver are required to provide a disturbance free solution. However, as all GPS receivers communicate with GPS satellites over the air interface; these are inevitably vulnerable to RF interference. This interference disturbs the timing receiver¿s performance, degrading its solution. This paper appreciates this issue, identifies the problems caused and discusses in detail the performance degradations of cellular networks due to instability of timing signals from GPS.
  • Monitoring of shrinkage and creep of concrete using fibre Bragg grating sensors
    (2006) Wong, Allan; Childs, Paul; Peng, Gang-Ding; Gowripalan, Nadarajah
    Conference Paper
    Fibre Bragg grating (FBG) sensors are used for the experimental investigation of two of the most important time-dependent properties of concrete: drying shrinkage and creep. A swept wavelenght system is used as the interrogation technique. The FBG sensors are embedded directly into structural grade concrete specimens. Standard mechanical method is used in parallel with embedded FBG sensors. Both mechanically and optically measured time-dependent strains are discussed. It is shown that the FBG sensors offer a better alternative to the conventional electrical and mechanical methods, in the measurement of long-term time-dependent strains.