QoS aware routing and wavelength allocation in optical burst switching networks using differential evolution optimization

The issue of burst losses imposes a constraint on the development of Optical Burst Switching （OBS） networks. Heavy burst losses strongly affect the Quality of Service （QoS） intended by end users. This article presents a QoS aware Routing and Wavelength Allocation （RWA） technique for burst switching in OBS networks. The RWA problem is modeled as a bi-objective Integer Linear Programming （ILP） problem, where objective functions are based on minimizing the number of wavelengths used and the number of hops traversed to fulfill the burst transmission requests for a given set of node pairs. The ILP model is solved using a novel approach based on a Differential Evolution （DE） algorithm. Analytical results show that the DE algorithm provides a better performance compared to shortest path routing, which is a widely accepted routing strategy for OBS networks.

Overview and progress of Chinese geographical human settlement research

Increasing Chinese urbanization and industrialization has prompted greater attention to the study of human settlement and the human-land relationship in the fields of geography, architecture, and urban planning. We used bibliometric methods and statistical software to review 180 articles on human settlement in 16 Chinese geographical journals. We found that Chinese geographical human settlement research is characterized by the following：（1） Most research focuses on human settlement extension, valuation indicators, models for urban and rural settlements, theoretical exploration and the planning practices of single-factor, human settlement and complex, geographical livability in macro-scale, urban settlement differentiation and ideal patterns in medium scale, the comprehensive evaluation of settlement environment, and the planning of community units in micro-scale, community settlements; socio-cultural investigation and warnings about advancing human settlement.（2） No progress has been made in synthesizing and integrating method systems. PSR models and DPSIR models are used for targeting mechanisms, while the standard settlement evaluation system was composed of physical ＆ economic indicators by questionnaire surveys. On the other hand, spatial clustering based on GIS has been a frequent focus in recent years. Pioneering research on human settlement and theoretical systems within the context of China＇s urbanization and industrialization will provide guidance on the sustainability of Chinese cities and regions. The following five aspects require greater attention：（1） Natural suitability research on human settlement, and a survey of human settlement demands to reflect the range of different demands concerning ecologically suitable settlements in urban environments, the corresponding valuation indicators, systems, and evolution, and the impact of the residents＇ socio-economic attributes.（2） Spatial-temporal evaluation and sustainability research on urban and rural human settlement at various scales, focusing on evolution and spatial differen-tiation at various scales such as city clusters and comparisons between cities, within the cities and communities.（3） Development of theory and technology for human settlement evolution research, including detection technology and methods, data mining measures, and forecasting and emulation of regional and urban human settlement evolution processes, mechanisms and patterns.（4） Research on the control of human settlement that focuses on optimization, patterns, and policies for effective management and development.（5） Estimating the human settlement system service value and establishing suitable human settlement systems, including social, economic, cultural and ecological service values.