Handoff Decision Process

Vertical handoff decision systems in the literature usually consider the only decision target of wireless infrastructure selection. On the contrary, since vertical handoff often requires also dynamic content adaptation, we claim the relevance of adaptation operation selection. Hence, PHD handoff decision process has the following decision goals, classified according to two primary sets.

For wireless infrastructure selection, the primary objectives are:

• Minimizing handoff latency;
• Considering user preferences on network interfaces;
• Minimizing transmission cost;
• Maximizing average throughput.

In the perspective of adaptor selection, the goals are:

• Choosing the compatible adaptation action with the highest possible quality for adapted content;
• Maximizing similarity in the matching between content profile and adaptor input.

In order to translate the above objectives into practical vertical handoff decisions without endangering service continuity, PHD employes MADM and fuzzy membership functions and adopts a two-step decision process. In the first step PHD dynamically ranks the possible target wireless infrastructures (wireless selection objectives). In the second step, it chooses the most suitable adaptation action and grants service continuity by checking that the following two constraints are satisfied: i) target IPR is compatible with terminal and network profiles; ii) the sum of wireless infrastructure selection time, adaptor selection time, and adaptation time, does not exceed prediction time-advance plus datalink handoff latency, as visualized in the figure.