4G is all about an integrated global network based on an open-systems approach. Integrating different types of wireless networks with wireline backbone networks seamlessly and the convergence of voice, multimedia, and data traffic over a single IP-based core network will be the main focus of 4G. With the availability of ultrahigh bandwidth of up to 100 Mbps, multimedia services can be supported efficiently. Ubiquitous computing is enabled with enhanced system mobility and portability support, and location-based services and support of ad hoc networking are expected. The illustration below shows the networks and components within the 4G network architecture.
With regard to network integration, 4G networks are touted as the hybrid broadband networks that integrate different network topologies and platforms. In the illustration shown, the integration of various types of networks in 4G is represented by the overlapping of different network boundaries. There are two levels of integration: the first is the integration of heterogeneous wireless networks with varying transmission characteristics such as wireless LAN, WAN, and PAN as well as mobile ad hoc networks; the second level includes the integration of wireless networks and fixed network-backbone infrastructure, the Internet and PSTN.
4G starts with the assumption that future networks will be entirely packet-switched using protocols evolved from those in use in today’s Internet. An all-IP-based 4G wireless network has intrinsic advantages over its predecessors. IP is compatible with, and independent of, the actual radio access technology. This means that the core 4G network can be designed and can evolve independently from access networks. Using an IP-based core network also means the immediate tapping of the rich protocol suites and services already available, for example, voice and data convergence, can be supported by using a readily available VoIP set of protocols such as MEGACOP, MGCP, SIP, H.323, and SCTP. Finally, the converged all-IP wireless core networks will be packet based and support packetized voice and multimedia on top of data. This evolution is expected to greatly simplify the networks and reduce cost for maintaining separate networks for different traffic types.
With regard to Ubiquitous Computing, a major goal toward the 4G Wireless evolution is the provision of pervasive computing environments that can seamlessly and ubiquitously support users in accomplishing their tasks, in accessing information or communicating with other users at any time, anywhere, and from any device. In this environment , computers get pushed further into the background; computing power and network connectivity are embedded in virtually every device to bring computation to us, no matter where we are or under what circumstances we work. These devices will personalize themselves in our presence to find the information or software needed.
To support ubiquitous computing requirements, 4G terminals need to be more intelligent in terms of user’s locations and service needs, including recognizing and being adaptive to user’s changing geographical positions, as well as offering location-based services [94]. Anytime, anywhere requires the intelligent use of location information and the embedding of this information in various applications. Outdoor wireless applications can use the Global Positioning System (GPS) to obtain location information. GPS is a satellite-based system that can provide easy and relatively accurate positioning information almost anywhere on earth. Many GPS implementations are available, including integrating a GPS receiver into a mobile phone (GPS/DGPS), or adding fixed GPS receivers at regular intervals to obtain data to complement readings on a phone (A-GPS), or by using help from fixed base stations (E-OTD). These implementations provide different fix times and accuracies ranging from 50 m to 125 m. For indoor applications, since GPS signals cannot be received well inside buildings, alternative technologies like infrared, ultrasound, or radio have to be used. Possible location-based services include finding nearest service providers, e.g., restaurants and cinemas; searching for special offers within an area; warning of traffic or weather situations; sending advertisements to a specific area; searching for other collocated users; active badge systems, and so on. Location information can also be used to help enhance other 4G network services; for example, by using location information to aid and optimize routing in mobile ad hoc networks. Geocasting is another new application that involves broadcasting messages to receivers within a user-defined geographical area.
In the future, it seems inevitable that mobile computing will flourish and evolve toward integrated, converged fourth generation wireless technology. Ad hoc networking will play an important role in this evolution. Its intrinsic flexibility, ease of maintenance, lack of needed infrastructure, autoconfiguration, self-administration capabilities, and significant cost advantages make it a prime candidate for becoming the stalwart technology for personal pervasive communication.
