Integration and Management of Multiple Radio Access Technologies in Converged Wireless Networks

Wireless communication networks enable customers to use communication services – like telephony or Internet services – at anytime and anywhere. A multitude of varying radio access technologies has been developed or is currently being developed. Those access technologies have different characteristics: they differ in their radio coverage, their spectral efficiency, cell capacity, and peak data rate; they can support different services; some support user mobility; they differ in their complexity and costs. For a network operator different radio access technologies may best be suited in different parts of the network, depending on the radio environment, the expected traffic pattern, and the anticipated services. The dynamic selection of access technology according to the communication requirements and network characteristics enable end users to be always best connected. Therefore, it is desirable to allow various access technologies to be combined in a common network and to allow interworking of different networks to be possible, even when they deploy different access technologies. The integration of multiple heterogeneous access technologies into a common network is referred to as network convergence. In this work we investigate technical solutions for integrating and managing different access technologies in a converged network and derive suitable network architectures. We define three types of functionality that are required for multi-access management: access monitoring, access selection and access handover. Access selection is the functionality that evaluates different accesses in order to determine which one is best suited for a certain communication session. This decision can be based on a number of parameters, like the characteristics of the radio link, the availability of resources in the different access systems, the requirements of the service, or policies of the user or network operator, which may depend on the business arrangement that the user has agreed to with the network operator. Access selection is performed by one or more multi-radio resource management functions which are typically located in multiple network nodes. Based on system simulations we evaluate the gain that can be achieved by access selection for different types of radio access technologies, radio network layouts, user distributions, and access selection algorithms. We show that the capacity gain of the system depends strongly on the considered scenario; in most cases significant gain can be achieved by access selection. We furthermore develop a model of a multi-access system that allows the system capacity to be derived analytically. Access monitoring it is the process of deriving useful information about accesses; it is a prerequisite for access selection. We present generic access abstractions that provide information about different accesses in a generic and comparable form. A generic link layer derives such abstracted information from access technology specific parameters. The generic abstractions provide information about the performance, as well as the resource situation for each access. The process of access monitoring depends on the connectivity state of a user terminal. Some types of information about an access system can be derived by making local measurements and observing access system information that is broadcasted in beacon signals; other types of information require that first a connection is established to the access system and the user terminal is attached to the network. We present different solutions on how suitable information about access systems can be obtained by the user terminal in different connectivity states. We develop a new network attachment mechanism that allows embedding access system information in the connectivity setup and network attachment procedure. We analyse this integrated network attachment procedure in a scenario where users evaluate