摘要：For a hierarchical cognitive radio network(CRN),the secondary users(SUs) may access the licensed spectrum opportunistically,whenever it is not occupied by the primary users(PUs).An important issue for this kind of CRN is the achievable qualityof-service(QoS) performance,such as traffic transmission delay,which is critical to the SUs' traffic *** this paper,we focus on the delay performance analysis of the SU system and the design of the corresponding optimal access strategy for the case of SUs sharing multiple licensed *** our analysis,the transmission of PU and SU traffic is modeled as M/G/1 *** merging the PU and SU traffic,we propose the model of a priority virtual queue on the licensed *** on this model,we obtain the expected system delay expression for SU traffic through M/G/1 preemptive repeat priority queuing *** the case of multiple licensed channel access,the access strategy is further investigated with respect to the expected system delay for SU *** minimizing the expected transmission delay,the optimal access strategy is modeled as a nonlinear programming problem,which can be resolved by means of the classic Genetic Algorithm(GA).Numerical results validate our analysis and design of an optimal access ***,by considering the time taken by the GA approach,we can also adopt the inverse proportional access strategy to obtain near-optimal results in practice.

摘要：在实验室环境下具体实现各种通信网络,并定量评估网络性能是各高校通信工程专业实验教改的重要方向。针对当前通信网络类课程在实验教学中存在的问题,梳理通信网络类课程的相关知识点,设计应用性和工程性很强的虚拟仿真实验项目,使学生掌握通信网络的建模方法和仿真技能,理解网络中各层的设计机制、算法和协议。

摘要：交换结构是高速路由器不可缺少的重要组件,在ns-2中仿真实现交换结构,目标是提供一个具有通用结构和基本功能的交换结构模型。通过队列父类的派生,修改原有的数据结构和分组处理流程,作为标准构件添加到ns-2的构件库中,用户只需在相应的功能函数中添加源代码,就可以开展与交换结构相关的研究工作。仿真结果与理论分析一致,动态跟踪表明开发的交换结构在网络环境中能够准确地转发分组,扩展了ns-2功能进行交换结构网络性能分析。

摘要：在网络优化上,WCDMA系统同样要考虑2G系统中关注的覆盖、容量、质量等问题,但WCDMA系统面临的新挑战还包括软切换开销控制、主控区和隔离区的精确控制、系统干扰控制等新问题。网络优化方法主要包括现网调查、网络性能分析、指定优化方案及方案的实施和测试。优化内容包括覆盖优化、容量优化和无线资源管理优化。

摘要：为了研究车载CAN总线网络系统的网络性能指标,选用通用CAN总线软硬件整合组成低成本车载CAN总线网络测试与仿真分析系统,对大众宝来车身舒适系统CAN总线网络进行测试与仿真分析.测试结果表明：大众宝来车身舒适系统CAN总线的节点平均发送CAN数据帧时间间隔为20 ms,数据长度为2~5位,网络通讯波特率为62.5 kBd,正常工作时网络负载为30%,系统后备能力强、可靠性高;仿真结果表明：车载CAN总线网络系统设计时节点测控数据定义较少的发送CAN数据帧时间间隔与数据长度、系统采用较高的网络通讯波特率,可以提高车载CAN总线网络系统性能.