In this chapter we have provided operational and functional details of a proposed protocol called MHD-CAR that has been designed in view of the stringent performance requirements imposed by fast moving MNs in terms of seamless and fast handovers in a heterogeneous wireless network environment. MHD-CAR optimises the standard CARD protocol in enabling a MN to discover on the fly the identity and capabilities of not only the neighbouring CARs but also CARs that may be located multiple hops away, and all this is achieved with minimum reliance on the network. This is expected to augment the performance of seamless handover protocols like FMIPv6 by ensuring accurate selection of NAR with minimum discovery latency. The MHD-CAR is a distributed mechanism in which the ARs are able to inter-communicate their identities and capabilities information to neighbouring ARs and to ARs that are located multiple wireless-hops away without relying on maintaining and managing a central CARD server. Each AR stores this information in their local CAR Tables which are then communicated to the MN upon request. Due to the distributed mechanism, MHD-CAR is more efficient, reliable, survivable and scalable protocol than the CARD protocol. Since the MHD-CAR does not introduce any new protocol messages it can therefore be easily integrated into the present deployment infrastructure. It exhibits far better performance over the IETF's CARD protocol in terms of the substantial reduction of signalling load over both the inter-AR links (by 17.5%) and crucially over the error prone wireless link (by 48%), while utilizing the CARD protocol messages. This reduction in signalling load is achieved because the MN is able to perform RAT and DCC functions locally, based on the information content of the NAN cache, and without relying on the network. Another very important aspect of the MHD-CAR scheme is that it provides cross-layer liaison between L2 and L3 mobility function. This is achieved by having a NAN cache in the MN, which provides the MN with a topological snapshot of the identity and capabilities of the access networks that may be multiple hops away from its present point of attachment. This enables a MN to perform target scanning on selected channels greatly reducing the CAP discovery latency and enhancing the accuracy of the TAR selection process. This alone will have a direct impact on the overall handover latency and fast moving MNs will greatly benefit from it. In contrast to the IEEE 802.21 standard, it is observed that the MHD-CAR is a light weight and much simpler alternative solution that provides the main functional services of the 802.21 MIHS. Although MHD-CAR has not been designed as an alternative to 802.21 but it does share its motivational, operational and functional scope. The IEEE 802.21 WG was developed to provide a unified global mechanism by defining a common MIH layer sandwiched between the Network Layer and the Data Link Layer and defined common triggers that would be generated independent of the underlying access technology. The motivation was to enable the MN to make accurate selection of the network and to provide triggers that would aid the IP mobility protocols like FMIPv6. However all this is being introduced at the cost of high complexity while deviating from the base ISO/OSI prescribed layered approach by introducing a new layer between the L2 and L3. Also it would mandate changes to the existing access technologies to confirm to the MIHS scheme of signalling. For example different SAPs are required to be defined for each of the access technology. It