Information theory and communication networks: an unconsummated union

Abstract

Information theory has not yet had a direct impact on networking, although there are similarities in concepts and methodologies that have consistently attracted the attention of researchers from both fields. In this paper, we review several topics that are related to communication networks and that have an information-theoretic flavor, including multiaccess protocols, timing channels, effective bandwidth of bursty data sources, deterministic constraints on datastreams, queuing theory, and switching networks.Index Terms-Communication networks, effective bandwidth, multiaccess, switching. I. INTRODUCTIONI NFORMATION theory is the conscience of the theory of communication; it has defined the "playing field" within which communication systems can be studied and understood. It has provided the spawning grounds for the fields of coding, compression, encryption, detection, and modulation, and it has enabled the design and evaluation of systems whose performance is pushing the limits of what can be achieved. Thus it constitutes a scientific success story of almost unparalleled proportions to which we pay tribute during this golden anniversary year of its birth.However, information theory has not yet made a comparable mark in the field of communication networks, the sister field and natural extension of communication theory, that is today, and is likely to remain for many years, the center of activity and attention in most information technology areas. The principal reason for this failure is twofold. First, by focusing on the classical point-to-point, source-channel-destination model of communication, information theory has ignored the bursty nature of real sources. Early on there seemed to be no point in considering the idle periods of source silence or inactivity. However, in networks, source burstiness is the central phenomenon that underlies the process of resource sharing for communication. Secondly, by focusing on the asymptotic limits of the tradeoff between accuracy and rate of communication, information theory ignored the role of delay as a parameter that may affect this tradeoff. In networking, delay is a fundamental quantity, not only as a performance Manuscript

A New Approach to Random Access: Reliable Communication and Reliable Collision Detection

“…Let be an arbitrary user subset. If the asymptotic conditional input distribution is continuous in at , then we must have (8) The achievability part of Theorem 2 is implied by Theorem 3 which is provided later in this section. The proof of Theorem 3 is given in Appendix B and the converse part of Theorem 2 is proved in Appendix A.…”

“…According to Fano's inequality [20], we have (19) For large enough , (19) implies that (20) where the second inequality is due to the "data processing inequality" [2]. Taking in (20) yields (8).…”

“…8 Note that, if the asymptotic input distribution P P P X is not continuous in r r r atr r r for allr r r satisfyingr r r = r r r , r r r r r r < r r r + 1 , then (27) may not be satisfied only by setting M at a large value. In this case, one needs to further partition the set B into a finite number of subsets, such that (27) is satisfied by messages within each subset.…”

“…Random channel access is therefore commonly seen in practical networks [8]. In random access communication, transmitters make distributed channel access decisions, such as whether or not to transmit a packet.…”

“…Networking practice allows bursty traffic arrivals and distributed determination of communication 0018-9448/$31.00 © 2012 IEEE parameters. However, the use of packet-based communication models and the lack of rigorous coding theoretic analysis essentially prevent an insightful understanding of the impact of physical layer communication to upper layer networking [8].…”