WiMax Operator's Manual

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CHAPTER 5 ■ STRATEGIES FOR SUCCESSFUL DEPLOYMENT OF PHYSICAL INFRASTRUCTURES 105 operator to execute. The first can be accomplished simply by building new base stations and backing down on the power levels of those already in operation, and the second relies on the intelligence programmed into the radio itself and not on the abilities of the network engineer. However, a few specialized software tools exist for frequency reuse planning that have recently become available for broadband wireless operators, and that you will consider in the following section devoted to explaining the basic principles behind cell mapping. Overall Strategies for Cell Mapping The first requirement of any strategy for cell mapping within a broadband network is flexibility and the scope to be able to factor in a vast range of transmission speeds and data rates as well as highly differentiated service offerings and user profiles. Obviously this entails considerable complexity in the planning tools. The older cell mapping procedures utilized by mobile telephone operators are themselves quite complex, but in many ways the situation confronting the fixed broadband wireless operator is such as to demand even more involved planning and plotting methods. Cellular telephone networks generally deliver fairly uniform service offerings, whereas wireless broadband networks must accommodate varying throughputs, some of which may be instantaneously user defined; a multitude of different service levels; and connections having widely varying fade margins. Furthermore, fixed broadband networks often have different subscriber densities and traffic volumes within various areas, but usage patterns are apt to be relatively uniform in mobile networks. The very large number of variables make network planning difficult in broadband fixedpoint networks, but both rules and resources are available, and the network operators should make themselves aware of them before a single base station is installed. Network Mapping Software Tools The network operator should always strive to plan the network systematically utilizing available software resources. Two companies in particular, Florida-based RadioSoft and Oregonbased EDX, specialize in offering mapping software to wireless operators. Both enjoy good reputations in the industry, and both support their respective products with consultation. True, both software packages incorporate known engineering formulas that can be abstracted from standard network design texts, but assembling such information and then attempting to apply it to the latest radios with the most abstruse advanced modulation schemes is an engineering exercise that could consume weeks. It is better to utilize the existing automated tools and improvise only when absolutely necessary. I particularly recommend the EDX software because it is so comprehensive. EDX Signal- Pro can factor in distance, blockage, radio sensitivity and selectivity, the use of advanced modulation such as OFDM and W-CDMA, adaptive modulation, a number of smart antenna technologies, and antenna polarization. In addition, it can set channel reuse patterns based on whether channels are defined as frequency divisions only (frequency division duplexing, or FDD) or as time slots within frequency bands (time division duplexing, or TDD). It can also profile every uplink and downlink as well as provide global readings for interference within an entire sector. Furthermore, it can calculate network capacities with various mixes of traffic—such as best-effort data, voice, multimedia, and so on—and includes three-dimensional mapping software, which shows building elevations and transmission paths. EDX software is widely used by the larger wireless carriers, but because of the considerable cost of a complete
106 CHAPTER 5 ■ STRATEGIES FOR SUCCESSFUL DEPLOYMENT OF PHYSICAL INFRASTRUCTURES package—upwards of $50,000—the smaller carriers that probably need the software the most have been reluctant to use it. One solution for the small operator who cannot bear the expense of purchasing the software suite initially is to utilize the services of a consultant who owns the package. Figure 5-2 shows the use of EDX software in Chicago. Figure 5-2. EDX software, courtesy of EDX Bear in mind that infrastructure products differ in their capabilities and that some of the newer technologies such as multiple-in, multiple-out (MIMO) antennas and frequency-agile radios may not be completely characterized in existing planning tools. Therefore, if one is contemplating the purchase of innovative technology to increase throughput or frequency reuse, one must make certain the vendor is willing to take an active part in the network planning process. Network Mapping Is Always Provisional Cell mapping is highly specific in terms of frequency band selected; modulation technique; the sensitivity of the radio; the types of services supported, such as best-effort high speed, access, voice telephony, rich multimedia, full mobility, and so on; and the distribution of subscriber sites. Should the network operator decide to transmit at another frequency than that used initially or attempt to offer services requiring constant throughput rates, the specific network architecture in use previously may not be adequate. It follows then that if the network at first offers only basic access but the intention is to move toward diversified services, then the network should be overdesigned in terms of basic access. A network that can support advanced multimedia well can nearly always provide basic access, but the converse is not true. The Importance of Projecting Growth Patterns A third consideration is closely related to the second. One should always keep in mind that bandwidth can be throttled down from a set maximum but never throttled up, at least not without major equipment upgrades. It follows that each cell should be designed to deliver however much capacity is likely to be demanded by the customers over the lifetime of the
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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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Page 162 and 163: Figure 6-4. Wireless public network
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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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