A key Fixed-Mobile Convergence driver is to provide ubiquitous high-speed wireless connectivity to mobile multimode terminals using cost-effective techniques. In such an environment, it will be necessary to support seamless handover without causing disruption to ongoing sessions. The achievement of this vision requires cooperative radio networks that share system information and assist in handover events resulting in a seamless end-user experience irrespectively of the application at hand.
For several years, service providers, telecommunication equipment manufacturers and other vendors have faced the great challenge of networks and services convergence. Beyond the core fixed infrastructure, which has already largely migrated towards IP, the explosion of broadband and, simultaneously, the launch of 3G mobile networks have accelerated the synergy between heterogeneous networks, leading to an all-IP network. As a result, the challenge of delivering services like voice, data, content, video communications and video broadcasting can be realized in a ubiquitous manner.
Legacy systems were designed and optimized without interoperability in mind, thus resulting in isolated communication networks with very tight bounds in geographical and service mobility. However, the advents of Beyond 3G have fuelled collaborative activities within the IEEE, IETF and 3GPP to construct a logical bridge between legacy systems to promote global roaming. Likewise, there has been recent interest from the broadcasting world to additionally integrate broadcasting services on a common service platform to address future market scenarios, thus raising significant future design challenges which include:
• New compatibility requirements to the IEEE 802.21 MIH (Media Independent handover) architecture to provide cooperative dialogue with the DVB networking world;
• The seamless challenge (vertical handover involving DVB is a technical challenge) since the networks may not be synchronized, and even the content stream may not be identical (i.e., for the broadcasting case, the compression rates may not be the same).
The optimized operation of all phases of a handover procedure taking also into account downlink-only technologies like DVB that create new business cases, constitutes an open R&D issue that could also affect the evolution and well establishment of Next Generation Networks (NGNs) that are going to stimulate FMC vision. Obviously, this operational optimization is tightly related to the dynamics of all handover phases (initiation, preparation, execution), as well as the interfacing of handover operation to upper service layers that assist seamless mobility and service continuity through MIP and SIP. A great research challenge that builds on top of recent research advances on both the handover procedure phases and upper service layers, is related with the investigation, design, implementation, testing and standardization of enabling technologies for optimized inter-system handovers operations among various radio cooperative networking environments (like 3G, WLAN, WiMAX and DVB) that are going to formulate future/near future business cases for both broadcasters and telecom operators in the context of a FMC communications environment. Alongside with this research challenge, 3GPP, IEEE 802.21, IEEE 1900.4 and IETF provide new functional blocks that aim to facilitate further inter-system handover procedures. However, from a systems perspective view, the ability of these functions to cooperate in a harmonized fashion still has to be evaluated. Equally important is to investigate the interactions among these functions and the functions of upper layers (MIP/SIP) in any IMS, pre-IMS, or combined network. Furthermore, the functional requirements for integrating other emerging technologies like DVB-T/H have to be identified and evaluated in an explicit manner. Towards this direction, a Task Group inside IEEE 802.21 has been recently formed to start the IEEE P802.21b project, which aims to investigate required extensions to the IEEE 802.21 standard to support handovers between 3GPP or IEEE 802, and DVB downlink-only technologies. DVB and other down-link only technologies pose extra challenges since a bi-directional physical link is not always available and services are primarily broadcasting-oriented
