Donna Michaels Sand

Seamless mobility across IMS and legacy circuit networks

The growing desire of network providers to introduce support for voice over IP (VoIP) has created interesting challenges in the area of interoperability with existing wireless circuit networks. The 3rd Generation Partnership Project (3GPP) and the 3rd Generation Partnership Project 2 (3GPP2) standards have defined the IP Multimedia Subsystem (IMS) as the platform for convergence. By definition, IMS is access agnostic; it provides services and features through a common core network, regardless of the means of transport. However, the IMS standards are just beginning to address the challenges associated with interworking with existing cellular circuit networks. Achieving seamless mobility involves supporting both roaming and handoff between networks. This paper discusses the issues involved in providing seamless mobility for subscribers across the packet and circuit domains and proposes network-based solutions.

Simulation of self-organizing spectrum management in wireless networks

We describe the simulation of a new dynamic channel assignment algorithm in FDMA/TDMA wireless networks. The algorithm relies on periodic interference measurements by each of the base stations on the inactive frequencies, so as to identify appropriate candidate channels. The adaptive nature provides automatic configuration at the time of system initialization and adaptation to system expansion and traffic patterns with spatial or temporal variations. By eliminating the manual frequency planning process inherent to todays fixed channel assignment procedures, the self-organizing capability guarantees ease of operation for service providers, while increasing both capacity and voice quality. Our simulation experiments demonstrate stability of the algorithm and confirm its self-organizing capability. They also indicate a significant decrease of call blocking and dropping and other quality-of-service improvements.