The NSF Division of Networking and Communications Research and Infrastructure (DNCRI) was established in 1987, shortly after the creation of the Computer and Information Science and Engineering (CISE) Directorate, with the goals of serving as the major catalyst within the National Science Foundation (NSF) for basic research and education in communication systems and networks and the infrastructure deployed in support of research and education.
To help focus research priorities, DNCRI has sponsored a series of workshops to assess its program and suggest future directions for communications and networking research which make the most effective use of limited DNCRI resources. These workshops have attempted to invite active participation by leading researchers in the field whose joint inputs have provided the content for the summaries and conclusions which form the bulk of the respective reports resulting from these meetings.
The first of these workshops took place in 1989 and was followed by a similar workshop in April 1992 to update the suggestions made in the initial meeting and to reconsider the assessment of research priorities in light of the rapidly developing nature of enabling theory and technology, evolving national needs and opportunities and the infrastructure requirements in support of research and education in the United States. A third workshop held in May 1994 articulated the major issues affecting networking and communications research for the future, including plans for the then rapidly evolving National Information Infrastructure (NII), and identified specific research priorities. An outcome of this workshop was the recommendation of four specific research initiatives, including one in wireless and mobile communication systems and networking.
The Wireless and Mobile Communications Workshop was organized under NSF sponsorship and held in March 1997 at the Airlie House in Northern Virginia, partially in response to the specific recommendation made in the 1994 workshop for a research initiative in the area of wireless and mobile communications and networking. The purpose of the workshop was to identify and characterize the major research issues associated with the design, development and deployment of future wireless and mobile communication systems and networks, to provide specific suggestions for focused research activities and to provide a contextual basis for effective crosscutting research which spans multiple layers in the networking hierarchy and combines communications and networking research.
There are currently approximately 40 million mobile cellular subscribers in the United States limited mostly to voice-oriented telephony services and interconnected in a relatively seamless fashion to the public fixed wireline telephone system. This phenomenal growth of mobile cellular telephony provides a clear demonstration of the significant value that users place on portability as a service feature. Indeed, the telecommunications industry expects that there will be about 80 million cellular and personal communications systems (PCS) subscribers in the North America by the year 2000. This growth will occur in an environment characterized by rapid development and migration of end-user applications and services towards Internet, World Wide Web (WWW) and broadband multimedia delivery over the evolving fixed wireline infrastructure. It seems reasonable to expect that this will precipitate strong consumer demand for wireless extensions of a similar array of user services. This inevitable evolution of wireless mobile services - to include data and multimedia delivery in addition to telephony service - poses significant technical and conceptual challenges. In particular, effective support of multimedia information services will require a major shift from the current circuit-switched wireless mobile infrastructure towards integrated services packet/cell switching architectures while addressing the significant challenges posed by the particular characteristics of the wireless mobile environment.
The most prominent characteristic of these future wireless mobile networks which differentiates them from fixed wireline networks is the requirement to share a limited spectral bandwidth while coping with the contention and mutual cochannel interference resulting from a large and variable number of randomly located and perhaps mobile users with diverse service and traffic requirements all trying to communicate with a relatively small number of access points to a fixed wireline backbone network. Furthermore, the wireless communication links themselves can generally be described as time-varying frequency-selective fading multipath channels. The topology, link performance and quality of service (QoS) delivered to user applications in this communications environment is characterized as highly time-varying. The research community faces formidable technical challenges in designing reliable wireless communication systems and networks that provide efficient bandwidth and power performance in such environments.
Another differentiating characteristic, especially in data networks such as the Internet or ATM networks, is that the user mobility that generally accompanies wireless access imposes new requirements on the architecture of these networks. Existing data networks, which were designed and implemented long before mobility was considered to be a serious option, must be extended to allow users to attach to different parts of the network and receive services as though they were attached to a fixed home location. To judge from the lack of commercial offerings in wireless mobile data networking, supporting this type of operation in today's data networks is a much greater challenge than simply providing roaming telephone service. Yet inroads are being made, and an increasing number of Internet users today enjoy mobility support. However, much work remains before there emerge wireless mobile networks that support multimedia, when one considers that today's data networks are not even able to provide a negotiated QoS to their users. A related characteristic is the evolution of new applications, made possible by mobility and ubiquitous access, that would normally not be found in fixed networks. Researchers in the field must understand and explore these problems, finding solutions that will integrate efficiently with existing systems and endure over time.
Workshop participants proposed a number of specific research priorities, outlined an approach for assessing the contextual systems basis for these focused research topics, and developed a number of suggestions for crosscutting research activities. Prior to the workshop, attendees submitted position papers that described their recommended priorities for research in the field. The position papers were discussed, and this discussion formed the basis for the research priorities identified by the workshop. Wherever possible, we have organized the topics into broad classes, attempting to impose order and structure on the wide variety of research issues, problems, and programs brought up during the workshop. Nine broad areas of research priorities, which are discussed in more detail in the workshop report, include the following:
Given the important distinguishing characteristics of the wireless environment, the mobile nature of tetherless users, and the influence these attributes have on the design and operating characteristics of wireless communication systems and networks, the workshop proposed a set of high-level descriptive features useful in characterizing wireless mobile communication systems and networks. These features provide a contextual basis for assessing the particular research issues addressed by specific focused research topics and projects. Furthermore, these descriptive features can be employed to establish a systems context which is useful for evaluating the important issues addressed by research that cuts across multiple subdisciplines. Several examples of this characterization were developed and are described in the workshop report, illustrating the utility of this approach. The specific high-level research issues, or descriptive features, identified at the workshop are:
These are important features for a wide range of communication systems and networks but are particularly useful in describing wireless and mobile systems. These issues generally cut across communication layers. Specifically, the workshop felt strongly that such crosscutting or cooperative efforts between communications and networking that addressed these issues at multiple protocol layers could provide an effective foundation in support of research in wireless mobile communication systems and networks.