【作者】 卜银娜；

【导师】 葛晓虎； 董燕；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2011， 硕士

【摘要】 切换是移动通信网络中的一项关键技术,它具有在终端运动或是恶劣的无线传输条件下恢复并保持通信的连续性以及平衡网络业务负荷等功能,直接影响着整个通信系统的服务质量和性能。切换判决作为切换中最为关键的环节,决定了切换的成功与否以及切换性能的优劣,是实现无缝切换的重要前提。在空天网络中,其信道特性不同于地面现有系统,接入的终端往往具有特定功能,并且运动速度非常快,甚至达到几倍、几十倍音速,可以用于切换判决和切换执行的时间非常短,这些特性形成了对高动态终端切换控制的重要技术挑战。本文首先基于STK平台进行建模,选择临近空间平台和GEO卫星组成的融合网络中五种典型切换场景,进行可视性分析、重叠覆盖区分析,以及终端接收信号强度分析。其次,在切换判决中,针对终端高速运动的特点,提出一个计算复杂度不高,预测精度满足切换判决要求的轨迹预测算法。然后联合高动态终端轨迹预测、业务质量和信号质量,设计了基于灰色关联系数和终端轨迹预测的多属性高动态终端切换判决算法。最后,设计了高动态终端轨迹生成算法,用于模拟高动态终端的运动,构成相应的切换场景,利用OPNET建立了五种仿真场景。在各个仿真场景中的仿真结果表明,所设计的多属性切换判决算法,与仅基于灰色关联系数的切换判决算法相比,不仅能够选择出最佳的目标接入点,而且能够及时触发切换,减少不必要的切换次数,避免“乒乓切换”;可以兼容同构网络和异构网络的切换判决。更多还原

【Abstract】 Handover technology is one of key technologies of the mobile communication networks, which can recover and maintain communication and balance traffic load in bad wireless channels and moving conditions. Therefore, the handover technology directly affects the quality of service and performance of wireless communication systems. As the most critical part of handover algorithm, handover decision impacts the success and performance of handover algorithm, moreover, it is an important precondition to achieve seamless handover in wireless communication systems. In Air & Space Network, characteristics of wireless channels are different from characteristics of wireless channels in existing terrestrial wireless communication systems. In Air & Space Network, terminals usually have high speed even up to several or several ten times of the speed of sound. Therefore, it is only a very short time left for handover decision and execution in Air & Space Network. These features conduce some great technical challenges for handover control algorithms of high speed terminals in Air & Space Network.Firstly, based on STK platform, five typical handover scenarios are selected to analyze the visibility, overlapping coverage and the received signal strength for a high speed terminal in Air & Space Network. Secondly, considering the high speed characteristics of the terminals, a trajectory prediction algorithm with low computational complexity is proposed for handover decisions. Simulation results show that the prediction accuracy of the new algorithm meets requirements of the handover decision. Furthermore, considering the trajectory prediction information of the high speed terminals and the quality of service, as so as the quality of signal, a novel multi-attribute handover decision algorithm is developed based on gray relational coefficient and the trajectory prediction information.Finally, a high speed terminal trajectory generation algorithm is designed to simulate movements of the high speed terminals to configure corresponding handover scenarios in Air & Space Network. Five simulation scenarios are established in the OPNET platform. Compared with the algorithm only based on gray correlation coefficient, Simulation results show that the proposed multi-attribute handover decision algorithm can not only choose the best target access point but also trigger the right handover time and reduce unnecessary handover times. Moreover, the proposed algorithm can be compatible with the handover decisions of homogeneous and heterogeneous networks.更多还原