The exponential growth of Internet-based services together with various access technologies and a wide range of mobile-networked devices have allowed users to be always connected'. However, no single technology can provide ubiquitous coverage and high throughput across all geographical areas and hence require inter-working of various heterogeneous access networks and technologies, a concept for the 4th generation networks. To provide true mobility, service providers (Telco) need a management system to authenticate and authorise users, to provide agreed-upon services and to negotiate roaming...