 the network; wireless gateway (WG): when there is an AR for wireless access; Fourth Generation Mobile Networks QoS broker: the entity responsible for managing one or more ARs and controlling user access and access rights according to the information provided by the AAAC system; AAAC system: the authentication, authorisation, accounting and charging system, responsible for service level management (including accounting and charging). 5.6.2 Quality of Service QoS architecture should lead to a potentially scalable infrastructure that is possible to expand to span large areas, to maintain contracted levels of QoS and ultimately to replace today's telecommunications infrastructure. No specific network services should be imposed by the QoS architecture. On the other hand, no special charging models should be imposed by the user-level AAAC system, and the overall architecture must be able to support very restrictive network resource usage. QoS architecture needs to provide different types of network-layer services, such as the Web, email, etc., and hence is a differentiated services approach. The architecture for QoS provision needs to consider multiple aspects: QoS provision both at the core and the access network, user and session signalling, integration of mobility and AAAC with a user-dependent QoS. Management in Mobile Networks Two layers are actually designed for the network service provision. They are: the service layer, with specific interoperation mechanisms across different administrative domains; the network transport layer, which will have its associated interoperation mechanism between network domains. An administrative domain may be composed of one or more network domains, but a terminal crossing over the administrative domains also changes its current network service provider. Each domain has an AAAC system and a QoS broker. When a mobile user enters the network, the AAAC will have to authenticate it and on successful authentication, it sends the relevant policy information based on the SLA of the user t