A new vertical handoff decision algorithm is proposed to maximize the system benefit in heterogeneous wireless networks which comprise cellular networks and wireless local area networks （WLANs）. Firstly the block pr...A new vertical handoff decision algorithm is proposed to maximize the system benefit in heterogeneous wireless networks which comprise cellular networks and wireless local area networks （WLANs）. Firstly the block probability, the drop probability and the number of users in the heterogeneous networks are calculated in the channel-guard call admission method, and a function of the system benefit which is based on the new call arrival rate and the handoff call arrival rate is proposed. Then the optimal radius of WLAN is obtained by using simulation annealing （SA） method to maximize the benefit. All the nodes should handoff from cellular network to WLAN if they enter WLAN＇s scope and handoff from WLAN to cellular network if they leave the scope. Finally, the algorithm in different new call arrival rates and handoff call arrival rates is analyzed and results show that it can achieve good effects.展开更多
快速城市化加剧了社会发展与生态保护之间的矛盾,如何利用集约的资源要素实现社会-生态效益优化,是城市可持续发展的关键。以上海市中心城区为研究对象,基于多目标规划(multiple objective planning,MOP)模型设置效益目标函数和约束条...快速城市化加剧了社会发展与生态保护之间的矛盾,如何利用集约的资源要素实现社会-生态效益优化,是城市可持续发展的关键。以上海市中心城区为研究对象,基于多目标规划(multiple objective planning,MOP)模型设置效益目标函数和约束条件嵌入斑块生成土地利用变化模拟模型(patchgenerating land use simulation model,PLUS),实现多元目标下城市绿地生态网络多情景模拟及功能评价,以期为未来城市绿地生态网络高效构建、土地利用规划决策提供参考。结果表明:1)耦合MOP模型和PLUS模型,基于土地资源多效益目标的定量化求解,可以寻求社会-生态效益最优化的关键拐点;2)不同效益目标导向下,可持续发展情景较经济发展情景和生态保护情景,耕地、林地、水域等各用地类型的相互转化,以及经济发展和生态保护之间的关系均处于相对稳定状态;3)可持续发展情景的各项绿地生态网络测度指标均介于其他2个用地情景之间,重要斑块的数量及空间分布表征,在优化社会-生态效益、城市土地利用结构配置的同时,城市绿地生态网络功能也得到提升。研究成果为超大城市高密区绿地生态网络结构功能完善、土地利用规划科学决策、城市社会-生态系统综合效益提升提供科学参考。展开更多
文摘A new vertical handoff decision algorithm is proposed to maximize the system benefit in heterogeneous wireless networks which comprise cellular networks and wireless local area networks （WLANs）. Firstly the block probability, the drop probability and the number of users in the heterogeneous networks are calculated in the channel-guard call admission method, and a function of the system benefit which is based on the new call arrival rate and the handoff call arrival rate is proposed. Then the optimal radius of WLAN is obtained by using simulation annealing （SA） method to maximize the benefit. All the nodes should handoff from cellular network to WLAN if they enter WLAN＇s scope and handoff from WLAN to cellular network if they leave the scope. Finally, the algorithm in different new call arrival rates and handoff call arrival rates is analyzed and results show that it can achieve good effects.
文摘快速城市化加剧了社会发展与生态保护之间的矛盾,如何利用集约的资源要素实现社会-生态效益优化,是城市可持续发展的关键。以上海市中心城区为研究对象,基于多目标规划(multiple objective planning,MOP)模型设置效益目标函数和约束条件嵌入斑块生成土地利用变化模拟模型(patchgenerating land use simulation model,PLUS),实现多元目标下城市绿地生态网络多情景模拟及功能评价,以期为未来城市绿地生态网络高效构建、土地利用规划决策提供参考。结果表明:1)耦合MOP模型和PLUS模型,基于土地资源多效益目标的定量化求解,可以寻求社会-生态效益最优化的关键拐点;2)不同效益目标导向下,可持续发展情景较经济发展情景和生态保护情景,耕地、林地、水域等各用地类型的相互转化,以及经济发展和生态保护之间的关系均处于相对稳定状态;3)可持续发展情景的各项绿地生态网络测度指标均介于其他2个用地情景之间,重要斑块的数量及空间分布表征,在优化社会-生态效益、城市土地利用结构配置的同时,城市绿地生态网络功能也得到提升。研究成果为超大城市高密区绿地生态网络结构功能完善、土地利用规划科学决策、城市社会-生态系统综合效益提升提供科学参考。
