Call admission control algorithms in OFDM-based wireless multiservice networks

Orthogonal frequency division multiplexing(OFDM) is becoming a fundamental technology in future generation wireless communications. Call admission control is an effective mechanism to guarantee resilient, efficient, and quality-of-service (QoS) services in wireless mobile networks. In this paper, we present several call admission control algorithms for OFDM-based wireless multiservice networks. Call connection requests are differentiated into narrow-band calls and wide-band calls. For either class of calls, the traffic process is characterized as batch arrival since each call may request multiple subcarriers to satisfy its QoS requirement. The batch size is a random variable following a probability mass function (PMF) with realistically maximum value. In addition, the service times for wide-band and narrow-band calls are different. Following this, we perform a tele-traffic queueing analysis for OFDM-based wireless multiservice networks. The formulae for the significant performance metrics call blocking probability and bandwidth utilization are developed. Numerical investigations are presented to demonstrate the interaction between key parameters and performance metrics. The performance tradeoff among different call admission control algorithms is discussed. Moreover, the analytical model has been validated by simulation. The methodology as well as the result provides an efficient tool for planning next-generation OFDM-based broadband wireless access systems.

Temperature measurement in children with cancer: an evaluation

There is little agreement as to the most appropriate thermometer, the anatomical site to carry out temperature measurement in children with cancer, or the type of thermometer preferred by the patients. The authors carried out this study to assess temperature measurement in children with cancer who were admitted for febrile episodes. The body temperatures of children with cancer who were admitted consecutively between January and October 2005 to the paediatric department because of febrile episodes were measured on admission and over the next 24–36 hours using an electronic thermometer sublingually as the standard reference site. These measurements were compared with those obtained with two ear-based thermometers, a forehead thermometer, and from the axilla (representing current practice). The parents were asked about the type of thermometer they used at home and the children were asked about the type of thermometer they preferred. There were 34 admissions during this period, of which 19 (56%) were confirmed as febrile. Altogether, 108 sets of temperature measurements were obtained, producing a total of 540 measurements from these admissions. Measurements with the two ear-based thermometers in febrile children achieved higher sensitivity than that with axillary and the forehead measurements. The ear-based thermometer was the most common type used at home while the forehead thermometer was the one preferred by the children. In conclusion, ear-based temperature measurements in febrile children were more accurate than axillary and forehead temperature measurements. The current practice of axillary temperature measurement needs to be re-considered.