WiMax Operator's Manual

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CHAPTER 5 ■ ■ ■ Strategies for Successful Deployment of Physical Infrastructures Success in launching a broadband wireless network largely depends on three factors: creating a service model that will attract subscribers, designing the network in all its aspects around that service model, and designing and implementing a physical infrastructure that will maximize coverage and spectral efficiency. This chapter focuses on the third factor. Selecting an Appropriate Network Topology Chapter 4 defines the basic network topologies and examines their basic capabilities. This chapter discusses where each is appropriate. Deploying Minority Architectures As indicated earlier, point-to-multipoint will be used in most instances to provide last-mile access to the subscribers to the broadband service. The question then arises, When does using the other topologies becomes necessary? Point-to-point connections are generally used in three instances: to serve a single site containing a number of high-value customers such as a business high-rise, to provide backhaul from a base station to a central office, and to serve a single high-value user requiring extremely high bandwidth such as a video postproduction house or a scientific research organization. In all three cases the full spectrum available to the network operator will generally be utilized within the single connection, and, to mitigate interference and maximize security, a very highgain, highly directional antenna will be employed. The tendency today is to use higher frequencies for point-to-point connections because generally abundant bandwidth is available in the higher bands and because they lend themselves to narrow-beam transmissions. The U-NII band at 5.8 gigahertz (GHz) is especially well suited to point-to-point links because it can be transmitted over long distances and because it will support throughput rates in excess of 100 megabits per second (Mbps). Point-to-consecutive-point architectures, also known as logical rings, are chiefly applicable with millimeter microwave equipment. Since no manufacturer of 802.16 equipment currently makes a complete system for supporting a wireless logical ring, I will devote little 101
102 CHAPTER 5 ■ STRATEGIES FOR SUCCESSFUL DEPLOYMENT OF PHYSICAL INFRASTRUCTURES attention to topology. A network operator wishing to use it will either have to jury-rig an IPbased system by utilizing Resilient Packet Ring add-drop multiplexers or use legacy SONET or synchronous digital hierarchy (SDH)-based point-to-point microwave equipment. Mesh wireless equipment, in its current state of development, is best suited to relatively small deployments serving a few dozen subscribers. To preserve bandwidth for individual users, routes must be kept short, that is, restricted to no more than two or three hops. Hundreds of subscribers distributed over several square miles would obviously lead to longer hop sequences and slower throughput speeds, and where subscriber bases of such size must be served, the network operator would have little choice but to create a number of discrete meshes, each with its own aggregation point, or else use another topology, most probably point-to-multipoint. Deeper into Point-to-Multipoint Point-to-multipoint architectures, as you have seen, are the norm in pervasive broadband metro deployments and always have been. The success of such deployments depends, on the one hand, upon reaching as many potential subscribers within the area swept by a single base station and, on the other hand, on utilizing the available spectrum efficiently and effectively. To illuminate how both objectives may be achieved, you must first examine the concept of wireless coverage areas, commonly referred to as cells, and how they figure in a point-tomultipoint architecture. Cells are the basic building blocks of wireless networks, and the mapping process of planned cell sites within a given territory to be covered constitutes the most basic strategic planning function of the network engineer. Radio Cells and What They Portend The concept of cells appears to have originated at Bell Labs, the research arm of the Bell Telephone system, back in 1948. At the time no effective means existed for automating the tuning function of individual radios to enable the concept to be realized, but later—30 years later, in fact—the Swedish telecommunications giant Ericsson would successfully demonstrate the feasibility of the concept in the first commercial cellular telephone system set up in the city of Stockholm. Today cellular architectures are ubiquitous in wireless communications, not just in cellular telephone systems, but in wireless local area networks (WLANs), personal area communications networks such as Bluetooth, and in fixed-point broadband wireless networks of the sort constituting the subject of this book. The Function of Cells in the Point-to-Multipoint Network To grasp fully the cellular concept, one must first understand how traditional radio networks operate, for the cell is a fairly radical departure from older practices and, at the same time, can really only be understood in their context. For as long as radios have been used, and they have been used for more than 100 years now, the typical approaches in two-way network communications have been either peer-topeer linkages where one radio transmits to another, as in a citizens band radio network, or arrangements where all of the individual user terminals go back to one central base station. The latter approach typifies the wireless telephone systems predating the cellular networks, the two-way dispatch radios used in commercial fleets, and police and public safety radios.
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WiMax Operator’s Manual Building
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This book is dedicated to my wife.
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Contents About the Author . . . . .
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■CONTENTS ix Performing Site Surv
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■CONTENTS xi Cyberwarfare . . . .
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About the Technical Reviewer ■ROB
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Introduction Broadband wireless has
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CHAPTER 1 ■ ■ ■ Wireless Broa
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CHAPTER 1 ■ WIRELESS BROADBAND AN
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14 CHAPTER 2 ■ ARCHITECTING THE N
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34 CHAPTER 3 ■ STRATEGIC PLANNING
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CHAPTER 6 ■ BEYOND ACCESS 151 som
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CHAPTER 7 ■ ■ ■ Service Deplo
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CHAPTER 7 ■ SERVICE DEPLOYMENTS O
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178 CHAPTER 8 ■ NETWORK MANAGEMEN
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CHAPTER 9 ■ ■ ■ Network Secur
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CHAPTER 9 ■ NETWORK SECURITY 189
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Index ■Numbers 2.4GHz to 928MHz b
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asic access and best-effort deliver
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■D dark fiber, features of, 75-76
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harmonics, impact on AC power, 188
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challenges to, 85-86 and NLOS, 121
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PONs (passive optical networks), fe
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signal diversity, providing with ad
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■V VDSL and entertainment service
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