The development and proliferation of wireless and mobile technologies have revolutionized the world of communications. Such technologies are evolving towards broadband information access across multiple networking platforms in order to provide ubiquitous availability of multimedia services and applications. Recent broadband wireless access systems include wireless local area networks (WLAN), broadband fixed wireless access (metropolitan networks) and wireless personal area networks (WPAN), as well as the widely used mobile access technologies, such as General Packet Radio Service (GPRS), Wide Code Division Multiple Access (WCDMA), Enhanced Data Rate for Global Evolution (EDGE), 3G and Beyond 3G (B3G) communications systems, Worldwide Interoperability for Microwave Access (WiMAX), and Bluetooth.
These wireless access technologies have characteristics that perfectly complement each other. Cellular systems and 3G provide wide coverage areas, full mobility and roaming, but traditionally offer low bandwidth connectivity and limited support for data traffic. On the other hand, WLANs provide high data rate at low cost, but only within a limited area, whereas WiMAX can supply mobile broadband for anyone, anywhere, whatever the technology and access mode. More specifically, WLANs are expected to provide access to IP-based services (including telephony and multimedia conferencing) at high data rates and reduced coverage in public and private areas. In particular, current WLANs offer a bit rate of 54 Mbps with IEEE 802.11g in the 2.4 GHz frequency band.
In this context, several types of WLANs are emerging and become profusely used, allowing users to roam inside their home, enterprise or campus without interrupting their communication sessions. They are organized in form of hotspots, i.e. relatively small networks covering a particular location providing broadband and easy-to-use Internet access to their customers while supporting high traffic load. Classical hotspot examples are airports, hotels, dense urban areas, campuses, and private offices. Using hot-spots, providers can offer subscribers not only wide-area connectivity through the cellular infrastructure, but also increased bandwidth viaWi- Fi access points deployed in high concentration areas. In this context, WLANs are often seen as a suitable complementary technology to the existing cellular radio access networks (2.5G/3G).
In order to provide the mobile users with the requested multimedia services and corresponding quality of service (QoS) requirements, these radio access technologies will be integrated to form a heterogeneous wireless access network. Such a network will consist of a number of wireless networks, and will form the 4th generation (4G) or next-generation of wireless networks. Heterogeneous wireless access, extensive support of IP-based traffic and excellent mobility support are among the main drivers for the architecture of such generation. The 4G wireless networks will offer several advantages for both users and network operators. On one hand, users will benefit from the different coverage and capacity characteristics of each network throughout the integrated networks. In this way, a large set of available resources will allow them to seamlessly connect, at any time and any place, to the access technology that offers the best possible quality. For the network operators, the integration of all these technologies provides more efficient usage of the network resources, and may be the most economic and technologically diversified means of implementing the future anywhere, anytime, always-on visions, providing both universal coverage and broadband access.
However, each access network provides different levels of QoS, in terms of bandwidth, mobility, coverage area and cost to the mobile users. As a result, when roaming across heterogeneous wireless access networks and experiencing vertical handoffs, high variability in the required QoS may be introduced, as the most optimal access network can dynamically change. In this context, roaming and interworking between heterogeneous wireless access networks constitute important issues to the networking community.
Moreover, the networks building the heterogeneous 4G system will be managed by various wireless providers and operators who have to cooperate and make different service agreements (service level, technologies, profiles, prices) to enable roaming access from and to their partners’ networks. In this context, mobile users will take advantage of suitable services and better service price, whereas providers will offer additional services with good quality and optimal network usage. Currently, wireless operators allow subscribers to roam into competing networks in order to offer ubiquitous connectivity. In the future, it is expected that wireless operators will continue to form roaming agreements with their competitors in order to maintain high customer satisfaction. This will enable customers to request advanced services and improved bandwidth when they become available, even if it is through a competing provider.
The 4G wireless networks will require a flexible architecture in which the QoS will be closely coupled with the resource management and handoff mechanisms of the wireless access technology. In this context, various architectures have been proposed for integrating WLAN and 3G (or UMTS) networks. Depending on the level of interdependence, the European Telecommunications Standards Institute (ETSI) specifies two generic methods for interconnecting WLANs with cellular or 3G networks: loose coupling and tight coupling. Loose coupling indicates a means of interconnecting both networks independently, utilizing only a common subscription, whereas tight coupling suggests that the WLAN plays the role of another access network to the cellular or 3G core network, i.e., both data and signaling traffic is transferred through the cellular or 3G network. Such integration methods may also be used for interconnecting WiMAX with other wireless networks. As a result, the integration of Mobile WiMAX and 3G/UMTS wireless networks may be considered equivalent to that of WLAN and 3G/UMTS wireless networks.
I believe in the end, the 4G definition will mainly be tied to user-centric approaches rather technlogy-centric definition. How we will use these technologies to enhance our living we greatly define the 4G EXPERIENCE.
