无线网络中跨层信息交互体系结构简介.ppt

无线网络中跨层信息交互体系结构简介 指导教师： 葛卫民 学生： 宋亚东 e.g. seamless mobility between GPRS and WLAN The MACs of GPRS and 802.11 interfaces are monitored for vertical handoffs. When network changes, active corresponding interface. SPO register with MAC TLs of GPRS and 802.11 for handoff event, when occur, SPO change the active interface at the IP layer using IP Tuning layer. Example2: Seamless mobility PO Why cross-layer ? Cross-layer examples Why cross-layer architecture ? MobileMan architecture ECLAIR architecture How to choose ? Outlines Rapid prototyping: easy development and deployment of new cross-layer feedback algorithm, independent with existing stack. Minimum intrusion: interfacing with existing stack without significant changes to existing stack. Portability: easy porting to multiple system. Efficiency: efficient implementation of cross layer feedback. Cross-layer feedback architecture design goals Choose the architecture that fits you ! * * * Why cross-layer ? Cross-layer examples Why cross-layer architecture ? MobileMan architecture ECLAIR architecture How to choose ? Outlines 无线网络的特点 Highly variable of wireless links ─ motion of device ─ surrounding physical environment change ─ interference change cause bursts of packet transmission errors Energy constraints ─ when increase transmission range ─ when forward packet for routing 无线网络的特点（cont.） Channel contention ─ hidden station ─ exposed station cause delay or link failure Problem with TCP ─ unable to distinguish congestion and other loss ─ suffer frequent route failures Tcp performance degrades Cross-layer（跨层） Application Transport Network Link/Mac Physical Application Transport Network Link/Mac Physical Horizontal Communication Vertical Communication Why cross-layer ? Cross-layer examples Why cross-layer architecture ? MobileMan architecture ECLAIR architecture How to choose ? Outlines Cross-layer feedback Physical Link/Mac←channel condition(e.g. bit-error rate) ─ adapt error control mechanism