To cope with these heterogeneities a common interconnection protocol which makes no assumptions about the characteristics of the underlying technologies is required.
The Internet protocol (IP) provides a universal network-layer protocol for wireline packet networks, and is viewed as an attractive candidate to play the same role in wireless systems. An all-IP wireless network, i.e. IP-based wireless access and fixed core, could make wireless networks more robust, scalable, and cost effective [2].
It will also enable the applications and software technologies
developed for wired IP networks to be used over wireless networks. An IP-enabled mobile device supporting multiple air interfaces could roam seamlessly among different wireless systems if IP is adopted as the common network layer protocol.