4th-generation Wireless Infrastructures: Scenarios and Research Challenges

" hot " item, frequently debated in the wireless community these days, is whether there is such a thing as a " fourth generation " (4G) of wireless systems that is likely to appear after the successful deployment of the current third-generation (3G) systems, say five to ten years from now. This new generation of wireless systems is supposed to complement and replace 3G systems, as well as second generation (2G) systems that have already been in use for about a decade. A " classic " approach would design such a " system " in the same way as previous generations of wireless systems, that is, yet again focus on higher data rates (now beyond 2 Mb/s) and find new frequency bands for a worldwide standard (e.g., [1]). For a number of reasons, however, it is not obvious that the roadmap is this straightforward. One of the main concerns is that 4G wireless infrastructures will be deployed in an environment where many other types of wireless , and wired, communications systems are already present. Furthermore, some people argue that future wireless communications will become focused on services and user needs, thereby forcing the mixture of available wireless infrastructure elements to be used in a more transparent way [2, 3]. In that case, the previously so important air interface standard and frequency band issues will become secondary concerns. By definition it is difficult to make precise statements on the nature of this kind of vision. An important factor contributing to this uncertainty is that we have very limited knowledge about the future environment in which a 4G wireless infrastructure should function. Which of today's systems will still exist when a potential 4G infrastructure is deployed? Which systems and solutions will be considered successful then? What technical bottlenecks will be apparent 10 years from now? What market impact will 3G wireless systems have? How will this affect user behavior and user demand? How much money are prospective users willing to pay for services provided over this infrastructure? As these questions indicate, defining relevant research topics with regard to future systems is not an easy task. Nevertheless , experience tells us that fundamental research related to 4G systems has to be carried out today in order to make it possible to deploy them a decade from now. We can thus formulate the key issue treated in this article: How can reasonably relevant research …