WiMax Operator's Manual

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CHAPTER 3 ■ STRATEGIC PLANNING OF SPECTRUM AND SERVICES 51 programming is well nigh impossible, and, in any case, customers may specifically want to have a high-speed link to their existing ISP. If that is the situation, working with incumbents makes good sense. VPN and Transparent LAN Virtual private networks (VPNs) and transparent LANs, also known as LAN extensions, are the most popular business-related services today and pose interesting possibilities for the network operator inasmuch as they do not need a lot of additional bandwidth beyond that required for simple high-speed access. They do involve additional investment in infrastructure and some fairly hard decisions on the part of the network operators based on their perceptions as to how the evolution of business data services is likely to proceed. A VPN is a secure communication from a remote location back to a corporate LAN that often involves encryption. A transparent LAN service takes the concept a step further by providing the remote user the means to run all LAN applications with similar ease at the remote location as at the corporate headquarters and not simply to access corporate databases. VPNs and LAN extension can be accomplished by various means. The older method is to utilize tunneling protocols and special hardware for performing the necessary encryption quickly. The preferred method today is to utilize a carrier-grade IP router or Ethernet switch with the built-in capability to set up Ethernet or IP VPNs. Such devices will exhibit a high degree of automation and scalability and low network overhead. Most edge routers sold today—that is, routers designed for use in a metro network— support IP VPNs through the agency of the Multiprotocol Label Switching (MPLS) ancillary protocol. Manufacturers of the latter include Cisco, Juniper, Laurel Networks, Riverstone Networks, TiMetra, and Vivace. Most of these products also include other functions such as Ethernet switching and ATM switching, though the precise mix of functionalities varies from one platform to another. Enhanced Ethernet switches form another possibility, specifically those designated as “metro Ethernet” and designed for the carrier marketplace. Atrica and Extreme Networks are the principal manufacturers in this category. But inasmuch as 802.16a networking products are based on IP rather than Ethernet, and because IP/MPLS has a much greater capability for setting various service levels to accommodate different types of customers, an edge router represents a better choice for enabling VPNs. Voice Telephony Another fairly obvious service offering beyond simple high-speed access is voice telephony. Either circuit voice or packet voice may be supported on 802.16a platforms, but circuit voice is quite bandwidth intensive, requiring the reservation of a 56 kilobit per second (Kbps) channel for each voice transmission. In contrast, IP telephony vocoders (digital speech compression devices) can operate at rates as low as 2Kbps with good fidelity. Fifty-six kilobits may not sound like much, but it takes only 24 voice circuits to eat up 1.5Mbps of throughput. If the total throughput of the available band is only 100Mbps, then a couple of thousand voice circuits could take up all the resources of the network. Another factor to consider when choosing between circuit voice and IP voice is the cost of the infrastructure. Circuit telephony is delivered within the metro via class 5 telephone
52 CHAPTER 3 ■ STRATEGIC PLANNING OF SPECTRUM AND SERVICES switches costing millions of dollars. IP telephony, on the other hand, is supported by softswitches, which are software emulations of circuit switching run over packet networks and utilizing large, hardened, general-purpose workstations such as the Sun Netra platform. Total cost is in the tens of thousands of dollars. Among the newer, specialized manufacturers, Sonus, Tacqua, Syndeo, and Oresis are prominent, and old-line equipment manufacturers that have added softswitches to their product lines include, most visibly, Nortel, Telcordia, and Marconi. Incidentally, hybrid softswitch/circuit switches exist, of which Nortel’s product has been the most successful. It should be noted that within the last two years VoIP architectures have been developed that can dispense with softswitches but only in cases where a pure IP network has been established between the two calling points. In cases where the call must traverse the public switched telephone network (PSTN), a softswitch will still be required. IP telephony may rightly be considered an emergent technology, one characterized by warring standards bodies and a lack of consistent, generally accepted approaches to network engineering. Some systems, for instance, use devices called gatekeepers that perform access control and address translation while others dispense with them. Conversely, some incorporate the switching and PSTN interface functions in a single box, and others favor a distributed platform. Another problem has been lack of real functional equivalence between traditional class 5 switches and IP softswitches. IP softswitches to date have not supported the entire myriad of features programmed into circuit switches, which in sum represent millions of lines of code. Another problem with IP telephony is the requirement for special customer premises equipment that will interface with standard desksets. If the subscriber is a business and already has an IP private branch exchange (PBX), that is not a problem, but otherwise voice will have to be recovered from the packet stream coming into the subscriber terminal and subsequently sent to the desksets via ordinary copper telephone lines. That often involves a separate black box, though some broadband wireless access equipment does support IP telephony today. As matters stand today, the wireless broadband operator is unlikely to be able to compete with the wireline incumbent as primary providers of voice services whether they offer circuit or packet voice services. Still, if the wireless operator is in a position to provide a subscriber expeditiously with extra phone lines, and the DSL or cable operator in the area cannot do so (or, for that matter, the telco incumbent), then the wireless operator enjoys an advantage. And, if the opposite is true—that is, if the competitive broadband access providers are offering secondline telephony—then it is incumbent upon the wireless service provider to match those service offerings. In the interest of broadening the service portfolio, the wireless operator should definitely consider offering long-distance voice service as well as local service. In this instance the operator will inevitably be functioning as a reseller, and the long-distance service itself may be a loss leader since the operator can compete only on the basis of price and can offer no unique calling features. One may question the wisdom of offering a service that is not in itself highly profitable, but studies have shown that operators providing the greatest number of converged services are likely to be the least affected by “churn,” the tendency for subscribers to switch service providers impulsively. Long-distance telephone services may be either traditional circuit, generally carried over ATM, or IP. If IP is chosen, make sure that specified peering arrangements are in place within end-to-end connections between both calling parties. Such peering arrangements involve the carriers providing long-distance data transport, and in the case of voice they must ensure low
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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
Page 22 and 23: CHAPTER 1 ■ ■ ■ Wireless Broa
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Page 85 and 86: 64 CHAPTER 4 ■ SETTING UP PHYSICA
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102 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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