Mobile data networks in the recent years have been kind of networks most developed due to advantage in flexibility and price of infrastructure. Technologies like WLAN that nowadays can be found in the most of the homes, the number of hotspots has been dramatically increased and also there are implementing new technologies as WiMAX have been role out by network operators to reach more coverage and capacity in order to bringing wireless access networks near to their users. A becoming mobile broadcast technology is DVB-H (Digital Video Broadcast - Handheld) that provide digital television, it is also interesting for operators because can achieve large number of users with minimum investment in infrastructure. Another aim of companies is to develop a heterogeneous wireless access network that users will be able to connect through the best available technology. In order to integrate these technologies in the heterogeneous wireless environment requires to provide mechanisms to allow network's interoperability. Create a seamless and transparent inter-system handover for the users is can be possible deploying a framework developed by IEEE 802.21 group. In addition, there is a problem that has to be considered. 802.21 framework cannot work on broadcast systems, must be required to implement a mechanism called Uni-Directional Link Routing created by the IETF in order to simulate bidirectional communication in unidirectional scenarios. First of all, in this essay, there is a description of several mobile data networks that can find on heterogeneous networks like the 802.11 family, IEEE 802.16 and the broadcast service to transmit digital television into handheld (DVB-H). In the second part, it is explained the different mechanisms to support mobility in heterogeneous unidirectional systems: IEEE 802.21 and UniDirectional Link Routing. Finally, there is practical part created by the tool "Network Simulator - NS2" simulating the traffic behavior in unidirectional systems.