WiMax Operator's Manual

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CHAPTER 4 ■ SETTING UP PHYSICAL INFRASTRUCTURE 65 Also, 802.11 airlinks may be useful for in-building extensions of the public network as in multitenant units (MTUs) and business parks, and their installation may be offered as a valueadded service by 802.16 network operators. What I do not advise is an attempt to deploy 802.11 WLAN equipment as the core infrastructure in a wireless broadband metropolitan network. Such a move is a false economy and is almost certain to result in a degradation in service that will ultimately cause the network to fail as a commercial entity. As indicated previously, a few products in the marketplace are based in part on the 802.11 standard but are provided with ancillary protocols and specialized interfaces that do represent legitimate attempts to modify the technology for use in the metro; however, such products almost invariably cost substantially higher than WLAN equipment, often double or triple the cost. Therefore, a decision to utilize equipment designed from the ground up for use in the metro rather than modified office equipment appears to make more sense. Obtaining Roof Rights, Right of Way, and Access to Appropriate Buildings at Acceptable Cost Almost every major wireless broadband operator faces the same challenge when planning and building the network. How does one manage to place network nodes where they are needed to serve the subscribers? If one does not meet this challenge early in the deployment process, one’s chances of succeeding with the operation will be nil. In the business of broadband services, access is everything—the absolute precondition to moving forward with provisioning and ultimately toward profitability. Access requirements for the network operator will vary somewhat according to the frequencies at which the network is operating, the types of customers sought, and the capabilities of the equipment. A network targeting primarily MTUs and business high-rises will need to get roof rights for the individual network nodes as well as the central base station(s). A network that is serving residential customers will not. A network using strictly line-of-sight equipment, will, all things being equal, require a denser infrastructure of base stations and thus will require more roof rights or tower rights than a system using the newer non-line-of-sight (NLOS) equipment. The cell size of the NLOS network will be smaller (see Chapter 5), but, on the other hand, each base station will be able to reach more potential customers located within its effective radius. To date, networks using line-of-sight equipment and operating in developed markets have nearly always failed because the expense of building and maintaining a large number of base stations has proven prohibitive. Central Office and Main Base Station Facilities Obviously, the first order of business is to establish a site for the initial base station and the central office for the entire network operation. The central office need not include all the administrative facilities of the network, but it should include the equipment essential for anchoring the network, which would ultimately depend on the mix of services offered by the network.
66 CHAPTER 4 ■ SETTING UP PHYSICAL INFRASTRUCTURE Several considerations are significant here. The antenna for the central base station needs to be situated at a position and at an elevation where it will encounter the fewest obstructions between itself and targeted subscriber sites and, as the network is built out, subsidiary base stations. This is true even if NLOS equipment is employed, because a clear line of sight is always preferable. Finding the right location can be difficult, though. A building that is considerably taller than any of its neighbors or a peak overlooking the city or metropolitan areas is often ideal from the perspective of minimizing obstructions, but it may be far from ideal in other respects. Space within the city’s tallest structure may simply be too expensive to rent, and a mountaintop is likely to be too remote to permit the placement of central office facilities. Another option is to place a steel antenna tower atop a shorter structure, but often local ordinances will not permit this. One can, of course, run a high-speed connection to a remote antenna, the usual practice among radio and television broadcasters, but that connection will have to be capable of handling all the traffic going through the hub with no bottleneck or reduction in throughput speed. A fiber connection of that type may be unobtainable or too expensive, and a wireless connection will have to be capable of fiberlike speed and of maintaining a high level of availability. This may entail leasing millimeter microwave backhaul from another service provider if one is operating in the lower microwave region. To obtain affordable space for central office facilities, one may have to settle for a location that is less than optimal in respect to signal distribution and customer acquisition, and such considerations will inevitably have an impact upon the network’s growth potential. Because the choice of central office and initial base station placement is so important, it is best for the network operator to select a site prior to proceeding any further with the network and make certain that it can be secured under favorable circumstances before constructing a single access point. Physical Requirements for the Central Office During the acquisition process, careful attention must be given to space, power, and ventilation requirements for the basic central office equipment as well as to the positioning of the antenna. The operator will need to know how many standard rack units of space will be taken up by the essential equipment and should have a fairly firm notion of what types if not brands of components will be purchased prior to network launch. Chapters 4–6 provide guidelines on what to look for in terms of equipment specifications. At the least, the operator will require the following components for delivering even the most basic service offerings. First, operators need a base station transceiver attached to the antenna. In some cases, this may be placed in a hardened enclosure adjacent to the antenna and in some cases in an equipment room or closet. Since cable that runs from the radio to the antenna should be kept as short as practical to avoid signal losses, it is not advisable to place the antenna on the roof of a 50-story high-rise and the transceiver in the basement. Typically, such transceivers are considerably larger and more powerful than subscriber units, and they feature redundant architectures and backup power. Therefore, they require a certain amount of space, preferably a sizable fraction of a cubic meter. Most broadband wireless systems also include a special component that incorporates essential software for managing the physical layer and may also include routing or switching software. In all cases, this box will include what is known as wireless middleware, which serves
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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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Page 35 and 36: 14 CHAPTER 2 ■ ARCHITECTING THE N
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Page 85: 64 CHAPTER 4 ■ SETTING UP PHYSICA
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Page 121 and 122: 100 CHAPTER 4 ■ SETTING UP PHYSIC
Page 123 and 124: 102 CHAPTER 5 ■ STRATEGIES FOR SU
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116 CHAPTER 5 ■ STRATEGIES FOR SU
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CHAPTER 6 ■ ■ ■ Beyond Access
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CHAPTER 6 ■ BEYOND ACCESS 133 Rou
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CHAPTER 6 ■ BEYOND ACCESS 135 (Qo
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CHAPTER 6 ■ BEYOND ACCESS 137 The
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CHAPTER 6 ■ BEYOND ACCESS 139 ins
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Figure 6-4. Wireless public network
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CHAPTER 6 ■ BEYOND ACCESS 143 sto
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Specialized Content Distribution Pl
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Beyond the Central Office CHAPTER 6
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CHAPTER 6 ■ BEYOND ACCESS 149 out
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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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