A single wireless user terminal should be designed, which can automatically operate in different heterogeneous access networks.

Problems related to high cost, limitations in terminal size, high power consumption, high circuit complexity, and unimproved analog-to-digital converter (ADC) performance in software defined radio (SDR)-based implementations.

The different software downloading schemes related to reconfigurable terminals have got their own problems.

A roaming user in a heterogeneous environment should be able to auto- matically track and select the available underlying wireless network. In each communication session for a particular service the most appropriate underlying network should be chosen.

The different software downloading schemes related to reconfigurable terminals have got their own problems.

Provision of personalized services through different personalized operating environments to the same address.

Confusions regarding the choice of either MIP or SIP as the core protocol and also whether the ideal framework be Network layer-based or Application layer-based.

To provide very high speed (streaming) video applications ensuring high QoS and bandwidth usability.

UDP suffers from acute congestion related problems, so TCP is gaining importance as the ideal transport layer protocol for video streaming. Opportunistic scheduling based video streaming needs more attention.

Users subscribing to multiple service operators for multiple different services should ideally be charged a single bill covering all the different billing schemes involved. Users need not worry about the different billing schemes.

Designing new packet-switched oriented billing and accounting policies for 4G users. From customers and operators points of view handling issues like QoS dependant charging, real-time billing information support, interworking prepaid systems support and billing support to diverse service accesses as well as cost calculation flexibility, IP traffic billing support, instant discontinuation of service if any fraud is detected and correct maintenance of customer’s profile, are the real problems.

Users should be able to roam freely and seamlessly across the various global geographic locations. Location and handoff managements should be done properly.

Maintaining high data rate, best possible QoS, reducing packet loss and signaling overhead are the primary challenges. The system throughput should be increased with low handover latency. In location management, issues like optimally handling diverse user calling and mobile patterns, and better inter-network location coordination should be handled properly. In handover