Call admission control and performance evaluation in wireless communication networks are essential for system design and operation. The network capacity and admissibility of imperfectly power-controlled multiservice code division multiple access (CDMA) system are studied in this paper. A generalized capacity formula considering traffic activity is derived, based on which a handoff prioritized call admission policy is presented and evaluated using the K-dimensional birth-death process model. System performance in terms of blocking probabilities, resource utilization and average system throughput are demonstrated and discussed in detail as the traffic intensity increases. It is also shown that the system parameters such as outage probability constraint and power control error have great impact on system capacity and performance. Since this work is based on the imperfect power control model, it is more appropriate to the design of practical multiservice CDMA networks.
Over the past half-century, the incidence of tumours has increased, resulting in cancer becoming one of the most lethal diseases in humans. In the present study, we elucidated the status of oncology research from 2001 to 2010. Studies published in 30 representative oncology journals were retrieved from the Web of Science (2001-2010) to compose our dataset. Knowledge domain visualisation, co-citation analysis and social network analysis methods were used. By mapping the oncology research performed from 2001 to 2010, we identified the primary research centres, including the top 20 institutions and countries and the 4 major oncology research fronts: i) the mechanism of abnormal oncogene expression; ii) tumour metastasis and angiogenesis; iii) the relationship between cancer cells and apoptosis; and iv) tumour vaccines. We also identified the 36 most collaborative academic communities, and multiple myeloma, angiogenesis and acute lymphocytic leukaemia were found to be the focuses of collaborative research in oncology from 2001 to 2010. Over the past 10 years, America has led oncology research, while China is the sole developing country to be ranked in the top 10. Analyses of the main research centres and forefronts may assist researchers in addressing these forefronts and ascertaining the developing trends in oncology. Analysis of the academic communities performing oncology research may provide scientific evidence and suggestions for policymakers to select the most prolific academic groups and leaders and to effectively manage and finance future oncology research. These selected groups and individuals will carry out additional joint undertakings and solve complex problems encountered in oncology research.
An optimum rate allocation scheme for code division multiple access (CDMA) uplink, which minimizes the average transmission delay of data users under the system resource constraint, is derived and evaluated in this paper. The average transmission delay minimization issue is formulated as a constrained optimization problem and solved using the Lagrange multiplier method. It is found that the proposed allocation rule achieves the minimum average transmission delay of data users compared to the other two conventional rate allocation schemes. Moreover, the proposed approach obtains much less transmission delay against the other two schemes especially when the traffic load is higher, which indicates that our scheme is more efficient in the high load systems. Numerical examples also show that the system parameters such as outage probability constraint and power control errors have great impact on the delay performance.Since our work is based on the imperfect power control model, it is more appropriate to the practical CDMA systems, especially for the delay-sensitive services.
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