WiMax Operator's Manual

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CHAPTER 7 ■ ■ ■ Service Deployments over Public Wireless MANs This chapter focuses on service deployment; specifically, it covers the deployment of valueadded services, which go beyond mere high-speed access and which serve to differentiate a service provider from its competitors. In this chapter, I go into considerable detail regarding standards and protocols and elucidate comprehensive procedures for implementing each type of service under consideration. As with so much else in this book, what follows is necessarily provisional simply because the standards, protocols, and physical platforms embodying them are in a state of flux and are likely to remain so within the foreseeable future. Introducing the Pure Packet Services Model As indicated many times previously, the aim of this book is to focus on packet services, specifically those using Internet protocols. This thrust is for a number of reasons. First among them is the growing consensus among industry analysts that packet networks will come to dominate telephony in the years to come, not only in wireless networks but in wireline as well. A transition from asynchronous transfer mode (ATM) to Internet Protocol (IP) backbones is rapidly occurring in the long haul, and IP voice and packet data services are beginning to displace circuit voice and traditional Time Division Multiplexing (TDM) synchronous optical network (SONET) data connections. Even mobile networks are beginning a slow but inexorable migration to pure packet. The second reason has to do with network efficiency. Packet networks are much more efficient than their circuit-based counterparts and will grow more efficient in the future. And because the wireless broadband operator is almost always challenged in respect to available bandwidth, network efficiency is no small matter. Furthermore, because wireline incumbents have been notably slow in migrating over to packet services, particularly IP voice and Ethernet and IP business services, the new wireless broadband service provider utilizing the latest high-efficiency packet switches and routers possesses the means of neutralizing to a considerable extent the incumbent’s advantage in overall bandwidth. By using and reusing available bandwidth with the utmost efficiency, the insurgent wireless service provider can frequently offer higher speed at lower cost than the incumbent—at good profit margins, to boot. 153
154 CHAPTER 7 ■ SERVICE DEPLOYMENTS OVER PUBLIC WIRELESS MANS The Packet Model and Converged Services The service model I propose is one of converged services. In other words, one network provides a multitude of diverse services. Traditionally, public networks have tended to be designed around a specific individual service such as telephony, video, text data, and so on, and the notion that one physical infrastructure could serve diverse needs is fairly recent. That this model will prevail in the future seems altogether likely, however, because growing numbers of broadband access providers have already begun to move toward it. Cable television operators now routinely offer telephone service and data as well as video programming, and telephone incumbents have begun to experiment with video over digital subscriber line (DSL). In this respect, broadband wireless is actually laggard, with most service providers still clinging to the pure access model. The remainder of this chapter discusses in detail how the various services are delivered over a converged network, specifically, a wireless converged network, though it must be said that in the case of certain services the delivery methods are still imperfectly realized. At the time of this writing, the fully converged network remains more an ideal toward which service providers are striving than a fully mature entity. However—and this cannot be emphasized too strongly—convergence is already well under way in a growing number of broadband local access networks. The key to convergence lies within the implementation of certain changes within layers 2 and 3 of the network, and within the last several years a multitude of protocols have been developed that will supposedly permit a packet network to emulate fully the characteristics of a deterministic network (in other words, a circuit network, so-called because the prior allocation of bandwidth that is the primary characteristic of a circuit network makes traffic flow highly predictable). The aim of such protocols is to preserve in large measure the bandwidth efficiency of best-effort packet networks while controlling traffic in such a manner that transmissions that require bandwidth on tap, so to speak, or that are intolerant of delays and timing errors will arrive intact at their respective destinations. This, unfortunately, is easier said than done, because it turns out to be extremely difficult to formulate rules that will meet simultaneously all the varying service requirements for diverse traffic flows while maximizing efficiency. In essence, in such a converged network the router is continually shuffling packets from various flows, holding them in buffers known as queues, and releasing them from the queues to take their place in a single stream representing the converged IP pipe. In some cases, the network controller will also be strategically dropping packets to maintain desired flow characteristics. No protocol yet has been devised that is completely successful in emulating the predictability in service levels associated with circuit transports while maintaining high efficiency, particularly in the face of increasing network congestion. Some protocols perform better during certain traffic conditions than others, but all misbehave under certain circumstances. Obviously, if the router had an infinite amount of time to scrutinize traffic conditions from moment to moment, it could devise compromises through brute-force iterative approximations that would promote equity while satisfying bandwidth constraints, but the router has almost no time, so a fairly rigid, rules-based approach is required. Because no rules yet exist that conduce to ideal network performance, the network operator has a dilemma. Currently, best-effort network traffic predominates within IP networks including the public Internet, so the problem is not yet acute. However, already IP voice telephony is beginning to expand rapidly, and with it the demands on the network for increased determinacy and predictable performance are increasing. A less rapid but still discernible expansion is occurring in
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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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64 CHAPTER 4 ■ SETTING UP PHYSICA
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100 CHAPTER 4 ■ SETTING UP PHYSIC
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Page 152 and 153: CHAPTER 6 ■ ■ ■ Beyond Access
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Page 156 and 157: CHAPTER 6 ■ BEYOND ACCESS 135 (Qo
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Page 162 and 163: Figure 6-4. Wireless public network
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Page 168 and 169: Beyond the Central Office CHAPTER 6
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Page 216 and 217: Index ■Numbers 2.4GHz to 928MHz b
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Page 220 and 221: ■D dark fiber, features of, 75-76
Page 222 and 223: 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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