Research On Association Control In Ubiquitous Network

Ubiquitous network extends the traditional concept of a communication network, breaks the boundaries between different communication networks and combines individual closed networks as a whole. Ubiquitous network is not only in the area of overlay networks, but also a complex of many things, such as terminals, services, data and protocols.On the one hand, each heterogeneous subnet in ubiquitous network coordinates with each other to jointly provide a transparent and seamless mobile network access environment. On the other hand, various services are fully interactive and adaptable automatically, which together create a wealth of service resources. These functions of ubiquitous network greatly improve the network service capabilities and provide terminals greater choices. However, the complexity and extensiveness of network and service bring many new challenges for network resource management. One of these challenges is how to effectively configure intelligent association relationship between the terminal and the network which is called network association control mechanisms.There have been lots of researches of network association control mechanisms that produce many practical solutions. However, the introductions of ubiquitous network appear as a network environment with more new features and services with new requirements. Therefore, the association control mechanisms of ubiquitous network are not confined to the existing boundaries, and will solve the problem on a larger dimension. This includes not only how to associate the terminals to available networks, but also encountering the collaborative optimization problems in a complex networks and services environment. In this thesis, the association control mechanisms of ubiquitous network are intensively studies to effectively improve the utilization of network resources and the service experiences of terminals. Specifically, this thesis proposes link stability based, content-aware based, transmission timeliness based and mobility supporting based association control mechanisms respectively in order to resolve the outstanding problems for different network scenarios. The main contents are as follows.Link stability based association control in ubiquitous networkTo begin with, this thesis studies the association control problem in low-speed mobile scenarios of ubiquitous network. When the terminals stay or move slowly in the ubiquitous network, the re-association due to the network migration and the degradation of link quality will lead to the increase of delay. Apart from that, the distribution imbalance of terminals in ubiquitous network will cause the imbalance load of networks and in turn affect the entire network efficiency. The delay caused by frequent handoffs and link congestion due to network overload are two main factors that damage the stability of the link. Existing research works on association control problems are mainly focus on reducing the delay of a single terminal handoff and increasing the duration of association, few of them take into account the joint effects of terminal handoff latency and network load balancing. To this end, we have studied the link stability based association control in ubiquitous network with the purposes of reducing terminal handoff frequency and balancing the network load through intelligent match between networks and terminals. Since the target problem is NP-hard, two constant approximation algorithms are presented to resolve it. Finally, trace based evaluations are conducted to demonstrate the effectiveness of our algorithms.Content-aware based association control in ubiquitous networkBesides, this thesis explores the association control problem in quasi-static scenarios of ubiquitous network. Ubiquitous network has a extremely complex service environment, and its key problems needed to resolve by association control are meeting the differential requirements of heterogeneous services while balancing the network load. Because of the lacking variety of services in traditional networks, existing research works on association control problems are chiefly concentrate on improving the throughput of network and establishing a fair resource allocation scheme among terminals. There is few effort to investigate the diversity of QoS requirements of heterogeneous services, and further consider jointly on the optimization between differential QoS requirements of services and network load balancing. In this respect, we have studied the content-aware based association control in ubiquitous network with the goal of meeting the differential QoS requirements for every individual service and balancing the network load. Since this problem belongs to NP hard, we then propose two approximation algorithms to resolve it. Finally, algorithms are evaluated in a network allowed several services. The results verify the performance of our algorithm. Transmission timeliness based association control in ubiquitous networkAlso in quasi-static scenarios of ubiquitous network, as the surge in the amount of data and higher requirement of improving the timeliness of data transmission, the association control mechanisms need to increase the throughput and reduce transmission delay. This is particularly important for widespread real time services in ubiquitous network. Due to the restricted size and capacity of traditional network services, the efforts committed to improving the timeliness of transmission mainly aim at a single access point or a single link. Apart from this, real time services are not widely deployed in traditional networks, with the results that existing research works on association control problems are chiefly concentrate on improving the throughput of network and balancing the network load. Few of the methods are conducted to incorporate transmission timeliness, and take another step forward in joint resource allocation for real time services. For this reason, we have explored the transmission timeliness based association control in ubiquitous network which targets at increasing the timeliness of service transmission and thus guaranteeing the continuity of service. After proof that the target problem is NP hard, we put forward two approximation algorithms to solve it. Finally, extensive evaluations show that the proposed algorithms have good performance.Mobility supporting based association control in ubiquitous networkLast, this thesis studies the association control problem in high-speed mobile scenarios of ubiquitous network. Since the topology of high-speed mobile network changes rapidly, load balancing is not a primary objective. The typical representative of high-speed mobile network scenario is vehicular network. In this thesis, we take vehicular network for example in studying the association control problems in high-speed mobile scenario of ubiquitous network. Excessive handoff frequency will bring high transmission delay to vehicular terminal services, while the instability of radio channel as well as the dramatic changes in vehicular terminal location will further deteriorate, leading to frequent interruptions for network links. In addition to this, unlike traditional wireless networks, the intermittent feature of vehicular network makes every work that tries to get long-term stability of the bandwidth nothing. There is little research on the association control mechanisms in vehicular network, which makes the vehicular network plagued by link instability and low throughput, and further handicaps the commercial deployments of vehicular networks. With regards to this, we have studied the mobility supporting based association control in ubiquitous network with the objective of decreasing the number of terminal handoffs, reducing the frequency of link interruptions and improving the network throughput. Two heuristic online algorithms are presented to resolve the target problem. Finally, comprehensive evaluations are conducted in vehicular simulation network to demonstrate the effectiveness of our algorithms.