5 ervasive and ubiquitous exchange of information is the idea behind most proposals for creating an integrated global information infrastructure (GII) [1, 2] in which users can freely move around, and still access public and private databases and communicate with each other in an efficient and cost-effective way. The global interconnec- tion network of computers, or the Internet, is an example of this trend where the number of users is increasing at an expo- nential rate. The introduction of wireless technology into the existing Internet together with the integration of different wire- less and high-speed wired networks can make it possible to achieve ubiquitous information exchange among geographically separated points with perceived quality and at affordable cost. In such a global information network, there are two major issues that must be addressed carefully. The first is the quality of service (QoS) and how the network can provide a perceived level of quality to users based on the application requirements and types of service. The range of those requirements could be very broad and may include allocated bandwidth, delay con- straint, data rate speed, error rate, or security level. For exam- ple, for a user trying music e-shop to listen online to a song, bandwidth and delay (as well as delay variation, or jitter) could be the most important QoS requirements. On the other hand, at the time of payment by credit card, the most significant issue will be the level of security provided by the network for elec- tronic transactions over the Internet. For another user, using the Internet to buy an item, for which all information is known beforehand and shopping is just a matter of order and pay- ment, Internet security would be the sole QoS issue. The second issue is the degree of mobility to be provided to users. Mobility was the igniting idea for wireless telecommuni- cations during development of the first generation mobile net- works in the 1980s. Wireless cellular communications have been developing since then (Fig. 1) toward the second-genera- tion systems, such as Global System for Mobile Communica- tions (GSM) and IS-95, and third generation (3G) wireless networks such as Universal Mobile Telecommunications Sys- tem (UMTS) and International Mobile Telecommunications (IMT-2000). In 3G networks, more features will be included to provide terminal mobility as well as personal mobility. The differ- entiation between these two comes from the way the moving object and the application are defined. In the former, mainly a single application such as voice has been considered, and there- fore a single terminal (i.e., moving object) such as a mobile handset could resolve the issue of mobility. In the latter, on the other hand, mobility is centralized around the person who uses the terminal for one or more applications. In this case, the user (now the moving object) has the choice of using his/her person- al account module, say through the subscriber identity module (SIM) in the GSM network, to any network-compatible termi- nal and to access any service provided by his/her network and supported by the terminal. This type of personal mobility will be well supported in 3G networks. In 4G networks, this type of mobility will be supported even more by introducing interwork- ing units (IWUs) that provide seamless roaming between net- works of different standards without any interruption in receiving ongoing service. Higher data rates and better quality in the new generation wireless networks promote cellular net- works for new Internet-based services. QoS and mobility are not mutually exclusive; indeed, they are strongly correlated. The perceived QoS is difficult to achieve in wireless networks with current technology. As an example, we have to accept the fact that the wireless channel for some time provides a much higher bit error rate (BER) as well as a lower data rate than wired networks. Higher reliabil- ity for such a high-BER wireless channel could, however, be obtained by implementing better error detection and correc- tion protocols at different layers of the network stack. Never- theless, some issues related to QoS are difficult to handle with any technique. Those issues are embedded in the nature of the equipment, such as size, the monitor resolution limitation of a mobile terminal, and the limited capacity of the battery. Currently, the majority of Internet-based applications are serviced completely or partially over the wired network where low BER and high data rates on the order of 100 Mb/s to a few gigabits per second are easily supported. Nevertheless, the emerging Internet applications will find their position in a mobile environment, as more people want to access database, e-mail, and information, or to do their shopping and trading when they have no access to a wired network. Both existing IEEE Personal Communications • June 2001 1070-9916/01/$10.00 © 2001 IEEE P The Role of Satellites in Global IT: Trends and Implications Abbas Jamalipour and Tracy Tung, The University of Sydney Abstract Satellite will continue to be an essential element in the establishment of long-distance telecommunications for many years, and it will have a major role in the implementation of the so-called global information infrastructure in the future. This is because of the particular feature of the satellite that can provide wide coverage independent of the actual land distance between any pair of communicating entities. The new generation of broadband satellite systems, which can provide high-speed data transmission and connectivity to terrestrial data networks, will create profound changes in all aspects of the emerging data communications applications such as Internet and electronic commerce. In this article we explore characteristics of the future satellite networks and their interoperability with terrestrial wireless and wired networks. The emerging data and IP applications impose new implementation issues on the long-latency and restricted satellite channel that must be resolved before such interoperability between satellite and terrestrial networks takes place.