Overview

This chapter provides an overview of the growth of wireless architectures that are challenged in terms of both capacity and density spectrum density, and outlines general options for addressing these challenges. One of the premises of this book is that the challenge of operating in dense spectrum will fundamentally change the nature of wireless operation for all spectrum-dependent systems, and that these changes will both require new technology (control, coordination, and decision making as examples) and create new opportunities to fundamentally extend the capabilities of wireless systems, ultimately to the point of comparability with wired delivery modes.

Although this book is not specifically about implementation of dynamic spectrum access (DSA), many of the techniques it describes assume DSA features will be present in future wireless systems. This is not an unreasonable assumption, insofar as both regulatory acceptance and technical necessity would appear to support this spectrum-access modality, for all emerging spectrum applications. DSA has many advantages in terms of enabling increased use of the spectrum, but it is also enabling for even more significant changes in wireless network operation, including the ability of nodes to mitigate interference to themselves from other nodes, locate frequencies with optimal propagation to achieve network density, and manage modulation and bandwidth.

Much of the DSA research literature focuses on achieving interference-free operation. Here, we will use the flexibility provided by DSA to manage a node's own environment.

Introduction

This chapter provides an overview of future wireless networking research needs, and the author's perception of the challenges and some of the obstacles that it faces. The field of cognitive wireless has existed in some form for well over a decade, at the time of writing, and yet no commercial or widely deployed implementations of it have even been seriously offered for deployment. Conference attendance primarily consists of academic researchers, with limited participation by several major corporate research organizations. There is little participation by the product-development community or venture-capital investors. The wireless technologies that dominate wireless operation had to leave the research community and be adopted as commercially and economically viable with cost and engineering feasibility. It is clear that current wireless research has not created the perception that is an essential element in the investment or product strategy for wireless advancement, at least in commercial practice.

This is not an argument against theoretical research. Quite the opposite; it is the basic theoretical research that will establish the argument that the benefits of this technology are universal and globally applicable to a wide range of architectures, not just those used as examples in a particular implementation. Showing cognitive features in a wireless fidelity (Wi-Fi) network will not be meaningful to cellular designers unless coupled with an argument that the reported benefits are much more universal and inherent than just to Wi-Fi.

For many decades, wireless designers have focused on range and link performance. In an emerging wireless-based economy, the need for high device and bandwidth density has begun to drive communications in an opposite direction, stressing spectrum reuse through short-range, highly localized communication architectures. Some of these adaptions are apparent now: low-cost femtocells fill a service gap between taller and higher-power cellular towers and the lower-power wireless local area networks; backhaul bandwidth to the infrastructure is as much of a constraint as the wireless up- and down-links; and wireless architectures have evolved to use a diversity of technologies, beyond cellular. Future communications architectures are unlikely to be a choice among cellular, wireless local area network, peer-to-peer, and fixed modalities, but will instead constitute an integrated framework whose optimizing process will be so dynamic that these modalities will be invisible to users.

Wireless technology is at a fundamental tipping point. The goal of new technology is not to “build out” and achieve spatial coverage, but to “in build” to achieve device and information density. Many of the fundamental principles that were appropriate to achieve network coverage are reversed when the objective of the network transitions to density and scalability. Additionally, future wireless environments will become much more heterogeneous, as they integrate multiple technologies; opportunistic, as dedicated spectrum is no longer available, and spectrum must be dynamically shared; and adaptive, as the technology must recognize the local challenges of coverage and density and adapt in situ.