  Heterogeneous Wireless Networks HWNs are combined networks made of different
Radio Access Technologies RAT. Next-Generation Networks NGN will provide high
bandwidth connectivity and high data throughput with smooth support for the
user's QoS requirements, in this context, users with multi-interface terminals
will be able to connect to different wireless technologies such as 802.16,
802.11 families and cellular families UMTS, HSPA and LTE in the same time. The
idea of NGN is that users will not be tied with a contract with one single
operator but, users will be able to choose the Radio Access Network RAT
considering the user's QoS requested. This paper focuses on the network
selection strategies and the inter technologies Handoff, we will present a
description of the existed methods of network selection, we will discuss the
merits and the weakness of such method and we will give our point of view.
