Research On Some Key Technologies Of Ubiquitous Network For Multi-Device Coordination

Along with the steady advancement of pervasive technologies, ubiquitous network is evolving towards a ubiquitous, convergent, heterogeneous, multi-device coordinated, mobile connectable direction. In ubiquitous network environments, in order to overcome the impact of different forms of resources, independent network architecture and varied management mechanisms, how to coordinate the different terminals, heterogeneous network as well as diversified services for the user, and evolve its function and mode, these will be challenges for multi-device coordination based on ubiquitous network.Holding such background, this thesis will focus on this topic with the mathematic help of pearson correlation coefficient, queue theory and so on. From a series of rational solutions of context-awareness service adaptation, QoS-oriented dynamic policy generation, multi-path transport control mechanism and cross-layer cooperation-based handover are proposed jointly with user similarity context, resources provisioning, admission control, available bandwidth measurement and load balancing. The major contributions of thie thesis are as the following:(1) According to the variety of services, the preference of users and the scheduling of network resources in ubiquitous network scenarios, this thesis presents a context-aware service adaptation mechanism under ubiquitous network relying on user-to-object, space-time interaction patterns which helps to perform service adaptation according to user’s contexts (such as preferences and habits), network context, service context and device context. Meanwhile, the proposed algorithm can effctively balance weighting factor of the user preferences and objective performance, by combining entropy theory and fuzzy analytic hierarchy process algorithm (FAHP). When similar users are equal to10, evaluation results prove that this mechanism can effectively increase the ratio of user satisfactory from0.7to5.5.(2) Multi-device service continuity with adaptive resources provisioning under ubiquitous network is proposed by combining the proposed framework. On this basis, it integrates resource reservation, service priorities and service degradation. This mechanism can effectively decrease the ratio of handover blocking probability from11.6%to20%.(3) A dynamic policy framework and its dynamic policy generation scheme are proposed for the problem that traditional policies cannot preferably get adapted to the ever-changing network. Based on the predicted information of the ever-changing network traffic, the mechanism chooses the template according to attributes and automatically produces dynamic policies through the analysis of network resources, extraction and standardization of key attributes. This makes the system management more and more automatic and autonomous. Finally, applying this dynamic policy generation scheme to ubiquitous network and further improving the system of load balancing from3.4%to11.7%.(4) Considering transmission characteristics under ubiquitous network, some key factors that influence the performance of multi-path transmission are well analyzed, current status of the research and some difficult issues are pointed out to improve the performance of multi-path transmission. This thesis proposes bandwidth estimation extension and congestion control modifications for mSCTP-CMT to improve the transmission throughput in ubiquitous network scenarios. The main contribution is to estimate available bandwidth and then to make judgment about packets are lost due to network congestion or not in order to fully utilize the value of cwnd which can efficiently utilize of send buffer, especially when frequency of loss events. Based on available bandwidth estimation, this thesis proposes an improved SACK scheduling optimization scheme for improving the transmission throughput in the multipath transmission environments consisting of asymmetric paths. In the proposed scheme, the main contribution is that a multi-homed receiver senses bandwidth values of all available reverse paths and then distributes SACK packets to each path proportionally. Simulation results prove that the performance of the proposed scheme could improve the application throughput under packet loss rate and time varied.(5) According to the perspective of multi-path transmission, a handover performance optimization scheme based on cross-layer cooperation is proposed. MIH module can collect the underlying link state information to complete discovery and handover decision in advance, and then transport layer module can complete the implementation of the follow-up handover process. Simulation results show that this scheme can effectively improve the application throughput.In summary, this thesis conducts a research deeply into ubiquitous network for multi-device coordination, and some suggestions to the future research are listed.