Research On QoS Guarantee In 802.11-based Wireless-cum-wired Network

With the rapid development of wireless devices such as wireless terminals, wireless access points and wireless routers, the applications on wireless network get popular. Wireless network has played an important role in extending Internet. Combining wireless network to wired network can provide more services, which is called wireless-cum-wired network. The proper next generation wireless-cum-wired networks include mobile IPv6 network and wireless mesh network based on IEEE802.11b/g standard. Mobile IPv6 network is a single-hop wireless network, and wireless mesh network is a multi-hop wireless network, both networks can act as the extension of Internet. Different from conventional wired network, wireless transmissions have some uncertain features, such as media sharing, high Bit Error Rate, easy to be interfered, hidden station/exposed station problem, mobility and so on. For these features, protocols used in wired network do not suit for wireless network any more. How to guarantee the quality of service (QoS) of real-time applications in wireless-cum-wired is an important issue. To solve the QoS guarantee problems in wireless-cum-wired network, some researches for mobile IPv6 network and wireless mesh network have been done in this dissertation, which include the end-to-end QoS guarantee method and seamless handover solutions in mobile IPv6 network, improving the performance and design the QoS aware routing method in wireless mesh network.To guarantee the end-to-end QoS in mobile IPv6, the De-Centralized Hierarchical Mobility IPv6 Managed QoS Architecture is proposed. The architecture distinguishes two mobile styles between micro-mobility and macro-mobility, and it is a scaleable and secure QoS architecture in mobile environment. The architecture defines the basic elements and how they are employed; also the concrete interaction work is described. Analyses and simulations are done to prove the effect of this architecture. The results show that the scheme is effective, and better than other solutions such as Nokia scheme, Mobi Dick solution and the SeQoMo projects.Mobile nodes roam randomly. To fasten the handoff with QoS guarantee, a new QoS context transfer solution named QoSCT is introduced. QoSCT combines fast-handover with context transfer protocol (CXTP). It taks MAC layer trigger as the context transfer point, and the QoS parameters is used in CXTP. QoSCT parallelizes network layer handover and QoS configuration, so it avoids Mobile Node's blindfold handover and resource waste. The extending method and working processes are described. Theoretic analyses and simulations show that QoSCT decreased the latency and jitter obviously and it can provide seamless handover, better than others' method.To provide a deployable mobile IPv6 network, a QoS Pre-Configure Mechanism (QoSPCM) is contributed to grantee QoS on DiffServ based Mobile IPv6 Networks. In this scheme, mobile IP is used to slove the handoff problem, DiffServ is used for QoS guarantee, and SIP is extended to perform AAA processes and distribute QoS parameters. QoS parameters are distributed in the session initiate process, and roaming users can keep communications with QoS guaranteed right after it performed handover. Voice software NICPhone and test-bed are implemented to demonstrate the validity of QoSPCM. Experiment results show that it is necessary to guarantee QoS for real-time applications on crowded networks, and mobile user can get the same QoS guaranteed after it performed handover on QoSPCM. The experiment also demonstrates the effection of DiffServ in congestion networks; high prior flows can get better service.There are multi-channels in wireless network. To prove that, experiments are done to demostrate the effect of interference between two data flows on different channels. The experiment results show that the packet loss rate and packet delay are different in these scenarios. It also proves there are three non-overlap channels in IEEE801.11b/g, which are channel1, channel6 and channel11. The data flows on non-overlay channlese can transmit with no packet loss and the least delay, that is, packets can transmit synchronously. To assign non-overlap channels on wireless mesh network, line-graph theory is introduced. The channel assignment problems can be solved by finding the Hamilton circles in line-graph. By assigning channel1 and channel11 to high propriety and busy wireless links and assigning channel6 to other links, four different algorithms are designed. By experiment, analyses and comparation, the channel assignment problem can be solved better by line-graph than by confict-graph. Using ling-graph to perform channel assignment is a new research topic.The QoS problems on wireless mesh network are defined. We find that the QoS solutions on wireless network should be done by QoS Aware Routing (QAR). Through analysising and comparing wireless mesh metrics, draw the conclusion that the ETX is the proper QAR metric. In diversit wireless mesh network, the packet transmit rate is dynamic. The ETX metrics do not work well in high diversity wireless mesh network. To solve the problem, an opportunistic routing method is designed, which uses both long-term metric and short-term metric as the routing metric. The method selects some candidate links by ETX, which is long-term metric and guarantee the QoS of traffics. By the short-term routing metric which is sensitive to time, the best link is chosen from the candidate links. The idea and processes of the routingmethod is described by examples, and ETX threshold and other parameters are analysed in a mathematic model. The analysis shows that the opportunistic routing method can get higher throughput with QoS assurance.