The next generation wireless networks will comprise interworking heterogeneous wireless access network technologies. The interworking of these networks will enable access ubiquity, hence mobility, particularly vertical handover between the networks becomes topical. Thus, coordination within this diverse environment in terms of handover management is required to improve the handover performance. Furthermore, it is recommended to maintain simplicity in the resource-poor mobile devices and yet keep them powerful for efficiently running rich real-time multimedia applications during mobility. Thus, this paper motivates that the handling of handover operations must be kept in the network infrastructure. Consequently, the vertical handover mechanism introduced in the paper exploits the advantages of network-based mobility management in heterogeneous wireless networks and proposes the incorporation of a network-based handover coordinator to improve the handover performance between the networks in terms of handover delay and packet loss. After all, mobility management protocols do not support seamless handover on their own. The handover coordinator, therefore, ensures that the vertical handover between the networks is transparent to active connections during the handover period. Simulation results show the benefits of the handover coordinator to the network-based mobility management in a heterogeneous wireless access environment in terms of reduced handover delay and packet loss.