The future next generation mobile networks will seamlessly integrate existing and new wireless network systems into an all-IP based network and hence will support a wide variety of wireless terminals which are referred to as heterogeneous terminals. And to support the mobility management requirements in the heterogeneous terminals, cross-layer design/optimization seems to be an interesting candidate.

Wireless networks have the characteristics of been volatile in nature and this resulted to an unstable connections between them (Cao, J., Wu, W., and Liu, X., 2010). Mobility management in a heterogeneous wireless network will be determined by the quality of the various networks and sometimes this problem occurs even within a network because the quality of connection varies. Due to the differences in the resources in the various networks, it is not easy for a mobile terminal to roam from one network to another for example, from 2G to WiMAX.
Similarly, the next generation heterogeneous mobile network is expected to accommodate many different mobile terminals (laptops, smart phones, etc.) with different resources such as processing power and technology. Hence, the mobility of such MTs in a heterogeneous network serves as a vital requirement in the design of a 4G heterogeneous network.
Since the heterogeneous network consist of various networks and MTs with different resources, the users are left with the option of selecting the network that best suit their requirements and “how to reflect different requirements of mobile users is not trivial” ( Cao, J., Wu, W., and Liu, X., 2010).
The traditional TCP/IP protocol stack is designed for fixed terminals and hence cannot support the required mobility in the 4G heterogeneous network. Each layer in the stack has a specific function to perform and depends on the information from the immediate next layer. For example, the transport layer depends on the network layer and does not consider the other layers like the link layer which is responsible for mobility. Hence, the need to devise a cross-layer mobility scheme for next generation heterogeneous network is vital.
The next generation mobile wireless network has the hallmark of heterogeneity and calls for a complete solution supporting all kinds of mobility anywhere and anytime.

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