This page intentionally left blank Emerging Technologies in Wireless LANs Wireless LANs have become mainstream over the last few years What started out as cable replacement for static desktops in indoor networks has been extended to fully mobile broadband applications involving moving vehicles, high-speed trains, and even airplanes An increasing number of municipal governments around the world and virtually every major city in the United States are financing the deployment of 802.11 mesh networks, with the overall aim of providing ubiquitous Internet access and enhanced public services This book is designed for a broad audience with different levels of technical background and can be used in a variety of ways: as a first course on wireless LANs, as a graduate-level textbook, or simply as a professional reference guide It describes the key practical considerations when deploying wireless LANs and equips the reader with a solid understanding of the emerging technologies The book comprises 38 high-quality contributions from prominent practitioners and scientists, and covers a broad range of important topics related to 802.11 networks, including quality of service, security, high-throughput systems, mesh networking, 802.11/cellular interworking, coexistence, cognitive radio resource management, range and capacity evaluation, hardware and antenna design, hotspots, new applications, ultra-wideband, and public wireless broadband “Benny Bing has created a masterful, horizon-to-horizon compendium covering the foundations, functionality, implementation, and potential-for-the-future of IEEE 802.11 wireless LAN communications Whether your interests are in QoS, security, performance and throughput, meshing and internetworking, management and design, or just the latest in Wi-Fi applications, you will find an indepth discussion inside these covers Emerging Technologies in Wireless LANs: Theory, Design, and Deployment is an excellent resource for anyone who wants to understand the underpinnings and possibilities of the Wi-Fi offerings we see evolving in the marketplace today.” – Robert J Zach, Director, Next Generation Broadband, EarthLink, Inc., USA “Over the past 20 years, wireless LANs have grown from technical curiosity to a mainstream technology widely installed across residential, enterprise, and even municipal networks The mobility and convenience of wireless has been augmented by the advanced throughput and range performance available in today’s products, extending the reach of wireless LANs to a broad array of applications This book explores all aspects of contemporary wireless LANs, from the basics through wireless security, meshes, QoS, high throughput, and interworking with external networks The broad range of topics and perspective make this the ideal reference for experienced practitioners, as well as those new to the field.” – Craig J Mathias, Principal, Farpoint Group, USA “This book is a wonderful resource for anyone who works with Wi-Fi wireless technologies It provides an excellent overview for the newcomer and an extensive and up-to-date reference for the expert This book is a crucial tool for everyone involved in this exciting, fast-paced field Everyone will learn from it!” – Professor David F Kotz, Director, Center for Mobile Computing, Dartmouth College, USA “The ability of Wi-Fi technology to expand in so many directions while maintaining backwards compatibility has been one key to its success and the technology will certainly continue to evolve This book has hopefully given you some insights into where we have been and where we may be headed.” – Greg Ennis, Technical Director, Wi-Fi Alliance Benny Bing is a research faculty member with the School of Electrical and Computer Engineering, Georgia Institute of Technology He is an IEEE Communications Society Distinguished Lecturer, IEEE Senior Member, and Editor of the IEEE Wireless Communications magazine Emerging Technologies in Wireless LANs Theory, Design, and Deployment Edited by BENNY BING Georgia Institute of Technology CAMBRIDGE UNIVERSITY PRESS Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521895842 © Cambridge University Press 2008 This publication is in copyright Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press First published in print format 2007 eBook (NetLibrary) ISBN-13 978-0-511-37105-9 ISBN-10 0-511-37105-5 eBook (NetLibrary) hardback ISBN-13 978-0-521-89584-2 hardback ISBN-10 0-521-89584-7 Cambridge University Press has no responsibility for the persistence or accuracy of urls for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate All trademarks mentioned in this publication are the property of the respective owners Use of a term in this publication should not be regarded as affecting the validity of any trademark or service mark While the publisher, editor, and contributors have used their best efforts in preparing this publication, they make no representation or warranties with respect to the accuracy or completeness of this publication and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose No warranty may be created or extended by sales representatives or written sales materials The advice and strategies contained herein may not be suitable for your situation You should consult with a professional where appropriate Neither the publisher, editor, or contributors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages Contents Authorship by Chapter Foreword Preface page xxix xxxiii xxxv Part I: Introduction to 802.11 Chapter - Emerging IEEE 802.11 Standards 1.1 IEEE 802.11n: Enhancements for Higher Throughput 1.1.1 802.11n PHY 1.1.1.1 MIMO 1.1.1.2 40 MHz Channel Binding 1.1.1.3 Beam Forming 1.1.1.4 STBC 1.1.1.5 Other 802.11n PHY Features 1.1.2 802.11n MAC 1.1.2.1 High Throughput Support 1.1.2.2 Legacy Protection, Coexistence, and Interoperability 1.2 IEEE 802.11k: Radio Resource Measurement 1.3 802.11p: Wireless Access for the Vehicular Environment 1.4 802.11r: Fast BSS-Transitions 1.5 802.11s: Wireless Mesh Networks 1.6 802.11T: Wireless Performance Prediction 1.7 802.11u: Wireless Inter-working with External Networks 1.8 802.11v: Wireless Network Management 1.9 802.11w: Management Frame Protection 1.10 802.11y: Contention Based Protocol 1.11 Conclusions 1 2 2 3 4 6 8 10 10 11 11 12 Chapter - Guide to Wireless LAN Analysis 2.1 Introduction 2.2 Overview of Wireless LANs 2.2.1 WLAN Physical-Layer Standards 2.2.1.1 802.11n 2.2.2 WLAN Regulation 2.2.3 WLAN Topologies 2.2.4 Establishing a wireless connection 2.2.4.1 Discovery 13 13 13 14 14 15 16 17 18 vi Contents 2.2.4.2 Authentication and deauthentication 2.2.4.3 Association, disassociation, and reassociation 2.2.4.4 Confidentiality 2.2.5 Security 2.2.5.1 Concepts of secure communications 2.2.5.2 Confidentiality and encryption 2.2.6 Collision Avoidance and Media Access 2.2.7 Physical Layer 2.2.7.1 Radio frequencies and channels 2.2.7.2 Signal and noise measurement 2.2.7.3 Encoding and data rates 2.2.8 Packet Structure and Packet Type 2.2.8.1 Data Packet Structure 2.2.8.2 Management and Control Packets 2.3 Wireless Network Analysis 2.3.1 Planning and designing a WLAN 2.3.1.1 Predeployment 2.3.1.2 Initial deployment 2.3.2 Managing a WLAN 2.3.2.1 Managing Signals 2.3.2.2 Managing Users 2.3.3 Administering a WLAN 2.3.3.1 Securing the WLAN 2.3.4 Troubleshooting - Analyzing Higher Level Network Protocols 2.3.4.1 Leveraging existing assets with AP Capture Adapters 2.4 Conclusion 18 18 19 19 19 20 22 24 24 26 27 28 28 29 29 30 31 32 32 32 32 34 34 36 37 38 Part II: 802.11 Quality of Service Chapter - WLAN QoS 3.1 Introduction 3.1.1 Terminology and Abbreviations 3.2 Channel Access 3.2.1 Legacy Channel Access Methods 3.2.1.1 Legacy Contention-Based Channel Access 3.2.1.2 Legacy Polled Access Protocol 3.2.2 802.11e Contention-Based Channel Access 3.2.2.1 TCMA MAC Protocol 3.2.3 802.11e Polled Channel Access 3.2.4 Illustrative Examples 3.3 Admission Control 3.3.1 Admission Control for Contention-Based Channel Access 3.3.2 Admission Control for Polled Channel Access 3.4 Power Management 3.4.1 Legacy Power-Save Mechanism 39 39 40 41 42 42 42 43 45 46 48 49 50 51 51 52 Contents 3.5 3.6 3.7 3.7 3.4.2 Automatic Power Save Delivery 3.4.2.1 Scheduled APSD 3.4.2.2 Full Unscheduled APSD 3.4.2.3 Hybrid Unscheduled APSD 3.4.2.4 Illustrative Examples QoS in Wireless Mesh Networks Summary End Note References vii 53 53 54 55 56 57 59 59 61 Chapter - Performance Understanding of IEEE 802.11 DCF and IEEE 802.11e EDCA 4.1 Introduction 4.2 IEEE 802.11 MAC Protocol 4.2.1 DCF Overhead 4.3 Performance evaluation of the IEEE 802.11 DCF 4.3.1 The Concept of Saturation Throughput 4.3.2 Maximum Saturation Throughput 4.3.2.1 Performance Bounds for 802.11b DCF 4.3.3 Saturation Throughput Analysis 4.3.3.1 Throughput Performance 4.3.3.2 Delay Performance 4.3.4 Non-Ideal Channel Conditions 4.4 MAC Enhancements for QoS Support 4.4.1 IEEE 802.11e EDCA 4.4.2 Further QoS Enhancement for Ad-Hoc Networks 4.5 Performance understanding of IEEE 802.11e EDCA 4.5.1 CWmin Differentiation 4.5.2 AIFS Differentiation 4.5.3 Coexistence of EDCA AC_BE and legacy DCF stations 4.5.3.1 Backoff Counter Decrement Rules 4.5.3.2 Analysis of AC_BE Default Settings 4.5.3.3 AIFSN=2 and Legacy DCF Stations 4.6 Conclusion 4.7 References 63 63 64 67 69 69 71 74 76 80 82 85 86 86 89 89 91 92 95 96 98 99 101 101 Chapter - Cross-layer Optimized Video Streaming over Wireless Multi-hop Mesh Networks 5.1 Introduction 5.2 Proposed integrated cross-layer video streaming 5.2.1 Wireless Multi-hop Mesh Topology Specification 5.2.2 Link and Path Parameter Specification 5.2.3 Application and Network-layer Parameter Specification 5.3 Problem Formulation 5.4 Video Streaming Optimization in the Multi-hop Mesh Network 5.4.1 End-to-End Optimization 105 105 107 109 110 111 112 114 114 viii Contents 5.5 5.6 5.7 5.8 5.9 5.10 5.4.2 Optimization under a certain Horizon of Network Information Complexity and Information Requirements of the Different Alternatives Experimental Results Further Reading Conclusions Appendix References 115 119 121 124 125 126 127 Part III: 802.11 Security Chapter - Understanding and Achieving Next-Generation Wireless Security 6.1 Overview 6.2 Risks of Wireless Insecurity 6.3 Understanding Wi-Fi Protected Access (WPA) 6.3.1 WPA TKIP 6.3.2 802.1X - User Authentication and Network Access 6.3.3 WPA Cracking Tools 6.3.4 WPA Summary 6.4 The Way Forward: Wi-Fi Protected Access (WPA2) and 802.11i 6.4.1 Increased Density of Access Points 6.4.2 Roaming Wireless Clients 6.4.3 Failover Requirements 6.5 WPA2: Under the Covers 6.5.1 WPA2 and 802.1X 6.5.2 WPA2 and TKIP 6.5.3 WPA2 and CCMP 6.5.4 WPA2 and Fast Roaming 6.5.4.1 PMK Caching 6.5.4.2 Pre-Authentication 6.6 Opportunistic PMK Caching: Fast Roaming at Its Fastest 6.7 Summary 131 131 132 132 133 134 134 135 135 136 136 136 137 137 139 139 140 140 141 141 143 Chapter - Wireless Local Area Network Security 7.1 Introduction 7.2 Current Application Solutions 7.3 MAC-Level Encryption Enhancements 7.3.1 The TKIP Per-Packet Hash Function 7.3.2 TKIP Temporal Key Derivation 7.3.3 Message Integrity Code 7.3.4 AES Based Encryption and Data Authentication 7.4 Secret Key Distribution and Generation 7.5 Authentication 7.5.1 802.1x EAP Authentication 7.5.2 EAP-MD5 7.5.3 EAP-TTLS 145 145 146 147 147 148 149 149 150 151 151 152 153 All Internet is Local 839 private sector owns the infrastructure, and an assessment of their risks and benefits to the public sector The Status Quo: The dominant business model for telecommunications networks in the United States is a network owned and operated by a private, for-profit company that is also the only or primary provider of monthly subscription services This is true of your local phone and cable companies They own the infrastructure, and you as a customer have no choice in who delivers the service This is true even with long-distance service; if AT&T is your local telephone company, you cannot get Sprint long-distance without also paying AT&T for use of the line Cities have little regulatory authority over these networks (As explained above, these networks are subject to few regulations at any level of government.) For example, they not have the authority to require phone companies to expand their DSL coverage, nor can they include provisions related to equitable or affordable Internet access in their cable franchise agreements Franchise Model: A privately owned and operated, for-profit network that does not have the city as a major customer The city grants the private company use of public assets for some period of time, and the company compensates the city for use of those assets.51 Cities typically work with a company that applies for a franchise and not issue a request for proposals (RFP), although some have done so as a way of soliciting competing offers One of the first wireless franchise agreements was in Anaheim, California Earthlink will pay the city a fee for use of the public assets needed to support a Wi-Fi network The city will not be an anchor tenant on Earthlink’s network, because it is deploying a cityowned Wi-Fi system for municipal use The franchise agreement does not include any requirements beyond the network providing a certain level of speed, coverage and reliability This model poses few risks, but also few benefits It requires no public investment and little public involvement of any kind The benefits are modest amounts of revenue from pole attachment fees, and the possibility of additional competition The city has little influence over the network coverage quality of service, or the prices charged Franchise models nothing to overcome the digital divide between higher and lower income households Anchor Tenant Model: A privately owned network, with the city agreeing to become the anchor tenant by agreeing to buy a minimum annual level of services The city grants the private company use of public assets (or assists in negotiating access from private entities52), and also agrees to be a major customer of the network (an anchor tenant) In exchange, the city is compensated for use of public assets The agreement contains a public benefits section that may include a share of revenue or limited free access to the network 51 If the new network will provide television (i.e., if it is a fiber optic network rather than wireless), the company may be obligated to meet the same terms as the existing cable franchisee, providing public access channels and meeting build-out requirements 52 In some cities, investor-owned electric utilities own the light poles Some wireless networks must also gain access to the roofs of buildings or other private assets 840 All Internet is Local One of the first anchor tenant models was in Minneapolis, as explained above Under the terms of the contract, the City will pay the private owner of the network a minimum of $1.25 million annually for services over the 10-year life of the contract The company will give five percent of net revenues to a digital inclusion fund managed by an outside foundation, and provide free access in selected parks and community technology centers The largest benefit of this model, in the eyes of many elected officials, is that the city does not have to finance construction of the network and assumes no responsibility for its ongoing operation The city gains a new competing network to its incumbent phone and cable companies, and receives funds for public benefit projects This model, however, does have substantial risks Since the city will rely on the network for its own internal communications and revenue for public projects, it cannot allow the network or the company that owns it to fail, even when its intervention contradicts the public interest Consider the recent case involving Massport (Boston-Logan Airport) Massport entered into an agreement with a private company that would provide for-fee wireless Internet access throughout the airport and share a portion of its revenues with the airport After the for-fee service was introduced, Massport tried to prevent airlines from offering their own free wireless Internet access in the airport The conflict ended up at the FCC, which eventually ruled in favor of the airlines, on the grounds that landlords cannot prevent tenants from using legal technologies of their choosing Cities also face the possibility that state or federal legislation will preempt their authority to enforce these agreements at some future date, as has happened with cable franchise agreements 38.7 The Dollars and Sense of Public Ownership Every city that is seriously exploring a citywide broadband network should a detailed economic and financial analysis This will serve it well even if it should end up choosing a privately owned system because it will allow it to negotiate with the private company from an informed perspective The analyses can use different assumptions Some of the issues involved are: • • • • • Who will manage the network? This may be the entity that owns the network, or management may be contracted out Will the network be for profit or not-for-profit? Will the owner of the network sell retail services only, wholesale access only, or a combination of the two? Will the city be a major customer? Will ongoing operations be supported by monthly subscriber fees, advertising revenue, sponsorships, municipal uses, or a combination of these? A complete analysis requires that the city examine different ownership structures A number of companies are offering to build networks at no up-front cost to the city City officials should understand that although seemingly attractive for its convenience, such a model may not offer the city and its households and businesses the best long term benefits A financial analysis includes several key items: All Internet is Local 841 Capital expenditures – Capital expenditures include wireless hardware and software, backhaul (the connection from wireless access points to the larger local network, which in turn connects to the global Internet network), network engineering and deployment It also includes core network equipment (i.e., servers and routers) The city’s existing assets – streetlights, electric poles, optical fiber connecting public buildings, etc – can significantly affect the cost of a network Costs depend on the technology Wi-Fi hot spots, like those found in cafes or homes, are inexpensive Ongoing costs may be as much as ten times the capital investment, however, since each hot spot must be connected to a wired connection in the existing lastmile infrastructure More typical is the use of Wi-Fi mesh that reduces the number of wired connections in the network by allowing information to hop from one access point to another before reaching a wired connection Wi-Fi mesh networks for municipal use only (public safety, meter reading, mobile municipal workforce) can be deployed for $100,000 or less per square mile Residential service networks, typically designed to reach 90 to 95 percent of homes and businesses, can cost upwards of $200,000 per square mile Fiber to the home is the most expensive alternative, but it is also the longest-lived and the only “future proof” option Estimates range from $600 to $3000 per home, depending on existing infrastructure and building density Operating expenditures – For municipal use only wireless networks, the rule of thumb is that operating expenditures are about 15 percent of capital expenditure annually This includes 24-hour network operations, pole attachment fees and electricity, monthly equipment maintenance and software upgrades, and Internet bandwidth For combination wireless networks, operating expenditures are about 30 percent of capital expenditure for a retail network, 15 to 20 percent for a wholesale network The added costs include customer service, billing and marketing as appropriate for retail or wholesale customers For fiber to the home, annual operating costs will be around percent of capital expenditure, though this may be slightly higher for smaller cities More detailed breakdowns vary by location For example, average pole attachment fees are in the range of $36 annually in California, but $86 annually in Louisiana Wi-Fi Access points with a single radio may draw $20 worth of power annually, while multi-radio deployments combined with high-powered wireless backhaul can draw five times more Wireless hardware maintenance will be in the range of to 10 percent of equipment costs annually (though this may be higher for some backhaul components) Internet bandwidth consumption will depend on the number of subscribers and the average bandwidth use per subscriber, generally assumed to be 250 kbps to 500 kbps per user on average, and Mbps per business on average Revenue – Monthly subscriptions are one of two major sources of revenue Monthly rates depend on whether the network is wholesale only or retail In a wholesale network, the city would be responsible for maintaining the network (or contracting for management) and relationships with companies that sell retail services In a retail network, the city would be responsible for retail service and support, as well as all marketing and advertising Gross wholesale revenue will typically be about one-quarter to one-third of gross retail revenue 842 All Internet is Local The wholesale rate that can sustain the network will depend not only capital expenditures and projected subscription rates, but also the division of responsibilities between the wholesaler and retailer(s) Fiber to the premises can generate much higher revenues than wireless, because the networks can support television The other major revenue category is municipal use Many cities currently budget for mobile computing, most often subscribing to cellular data services that are both slow (half the speed of a typical DSL or T-1 connection) and expensive ($60 per month) Within the city, the Wi-Fi network replaces these subscriptions, directly saving the city hundreds if not thousands of dollars each month Other direct savings may come through replacing leased lines to public buildings with fiber or high-speed wireless connections that provide faster speeds at a lower price, or replacing local-use cellular phones with Wi-Fi phones Cities that have invested in fiber connecting public buildings typically have a five to eight year payback relative to the expense of leased lines Advertising may be a source of revenue for wireless networks, but it would be unwise at this point for a municipality to count on that as anything other than an added benefit of perhaps one or two dollars per user, per month To put it in context, that might be enough to cover the Internet bandwidth to support a free-to-the-user service, but little more The most challenging aspect of the evaluation will be to estimate second order effects Some can be evaluated directly For example, if the city has a choice between hiring a new building inspector or using wireless to improve the efficiency with the same number of inspectors, the salary of the inspector not hired can be credited as an avoided cost But there is also a wide array of machine-to-machine communications (automated meter reading, wireless parking meters, traffic monitoring, etc.) that may improve provision of municipal services but not directly reduce the city’s expenditures If the city is planning to purchase these as communications services from a private network owner on a per unit basis, the value of the cost savings must be directly determined Many of these are zero marginal cost applications, which is to say there is no additional cost beyond that of the hardware, that are essentially free to the city if it owns the network There are other, less tangible but very important benefits the city should take into account, including economic development, reducing the digital divide, and increasing municipal efficiency and service levels The city should also take into account the citywide impact of reduced rates due to competition Sometimes cities see this as a disadvantage They worry that incumbents will reduce their rates below those of the city owned network In no case of which we are aware, did this result in a city network’s losing substantial amounts of money Moreover, the city, by the nature of its mission and charter, should have a broader balance sheet A drop in prices by incumbents by $10 per month translates into millions, perhaps tens of millions of dollars in collective savings to city households and businesses That not only enriches their individual balance sheets, but the respending of a part of these savings will enrich municipal coffers as well 38.7.1 Risk Any financial analysis must analyze risk as well as return There are two primary risks involved One involves technology, the other subscription revenue All Internet is Local 843 Technology – The biggest decision cities must make is whether to deploy an inexpensive wireless network or invest in fiber to the premises An all-wireless network has lower up front costs The capital cost of a wireless network with fiber backhaul is as much as onethird higher, but leaves the city with a tangible asset with a lifespan of thirty years or more A fiber to the premises network can cost ten to twenty times as much as wireless, but can carry all of a city’s information and communication traffic for decades to come When it comes to the question of ownership, the most important part of the system for a city to own is the fiber infrastructure However, many cities have chosen to own the WiFi hardware because of its low investment and the fact that the investment can be paid off quickly Standard depreciation for wireless components of a network is years On the other hand, it may be attractive for the City to contract with one or more private companies to install a wireless system and lease access to the City owned fiber network Households and businesses in cities that are touting low cost city-wide wireless are quickly learning there are often additional hardware costs Although Wi-Fi is installed in most laptops, and Wi-Fi cards are widely available for desktop computers, many users will require additional equipment to connect to outdoor wireless from the interior of their homes or businesses Often this has less to with the strength of the signal from the wireless node than it does with the strength of the signal from the wireless connection in the user’s computer This is not a barrier to deploying a Wi-Fi network, but the cost of socalled customer premises equipment (currently around $100 but falling) and who will pay it must be factored into network planning A second decision is whether, if a city chooses wireless, it should commit to Wi-Fi with WiMAX on the horizon The important difference between Wi-Fi and WiMAX is that the former uses unlicensed spectrum with power restrictions and smaller coverage areas, while the latter uses licensed spectrum that allows for higher power and therefore covers larger areas Deploying WiMAX will not be an option for anyone, municipalities or otherwise, who does not hold licenses for spectrum in the bands that will most likely be used for WiMAX equipment in the U.S What is the risk of technological obsolescence? Fiber is, for all intents and purposes, a future-proof technology The greatest expense is in installing the fiber The electronic equipment used to “light-up” the fiber can be upgraded over time Wi-Fi hardware is assumed to have a lifespan of five years, with software upgrades in the third year Given that the useful life exceeds the payback period, and the investment itself is modest, the risk of obsolescence in Wi-Fi is minor A risk does arise if a city system depends on proprietary technologies Wi-Fi is an open standard, meaning it is available free of charge to any one who uses a Wi-Fi device Users interface with wireless mesh networks via Wi-Fi, but most hardware vendors rely on proprietary software for the network backhaul (the connection from the access point to the larger local network and the national and international Internet) There is no similar standard for mesh networking Vendor bankruptcy, or even failure to invest in ongoing software development, could shorten the useful life of the wireless hardware Project pricing – Vendors in this field deem pricing to be proprietary information They are unwilling to provide pricing information outside of a closed request for proposals process, and when they so, are unwilling to itemize the bid components This can make it very 844 All Internet is Local difficult for cities to estimate the actual costs for their specific circumstances Under these circumstances, cities should insert contract provisions that shift the risk of cost overruns to the vendor Subscription rates – Subscription rates may not meet targets for any number of reasons, but increased competition is the most likely cause Existing service providers may add services they previously did not offer or lower their prices in response to the new network While this is problematic for private companies, it is no less a win for the policymakers that chose to build the new network After all, regardless of whose customers they are, they are all constituents The city’s options for dealing with this risk are substantially different between publicly owned and privately owned networks If the city owns the network, the question is how much the city owned project can afford to lose while still generating a net benefit for the community The private sector benchmark is a return on investment of 30 percent or more within years Municipal projects also must recoup their original investment, but they have greater flexibility than privately owned networks both in the payback period, and in the willingness to accept indirect and community-wide benefits as part of the return For example, Saint Louis Park projects its network could lose between $240,000 and $1.4 million over five years if projected subscription rates are not obtained On a per household basis, that is $2.31 to $13.48 per year If competition drives prices down to $20 from the current $35 for DSL-equivalent service, and $30 from the current rates of $45 for cable equivalent service (both are rates that the new network will charge), households will save $180 per year If the percentage of households with Internet access remains the same (an unlikely prospect, given the substantial reduction in price) the community as a whole will gain more than $12 million over five years, or more than eight times what it stands to lose in the worst case scenario 38.7.2 A Note About Municipal “Failures” City leaders considering municipal high-speed information networks may well come across reports, largely from anti-government think tanks, of municipal “failures.” They should be cautious about taking these reports at face value Here are some examples of such “failures.” Bristol Virginia Utilities (BVU): The Heartland Institute insists that BVU is a failure because “its operating budget is growing at an unexpected rate.” Facts: The Bristol City Council approved “OptiNet,” a municipal fiber-to-the-home network operated by BVU, in 2001 In July 2003, OptiNet launched services after being delayed more than a year by legal challenges from the incumbent phone and cable companies Throughout this time, it had to bear legal costs without revenue Nevertheless, financial performance was 20 percent better than projected for the first, traditionally difficult start up years Currently, the network is taking in more revenues than the sum of all its cash outlays, including debt service and interest Bristol is a town of 17,400 in Appalachia, a region hit hard by the decline of mining, farming and manufacturing Median household income was $27,389 in 2000, one-third All Internet is Local 845 lower than the national median of $42,151 The City Council and BVU view OptiNet as an economic development tool The network is credited with helping attract 700 new jobs in 2005 Cross Stone Products moved a 30-employee operation across the state line to take advantage of high-speed connection Two technology companies, Northrup Grumman and CGI-AMS, are building data centers that will create 1500 high paying jobs.53 The success of the network led neighboring Bristol, Tennessee to build its own fiber to the user network Cedar Falls Utility (CFU): The Heartland Institute cites CFU as a failure, principally for not generating enough free cash flow to finance its expansion.54 Facts: CFU started offering cable television in 1996 and high-speed Internet in 1997 Subscriber revenue has exceeded operating costs and debt service every year since 1997 No tax dollars have been used Voters approved issuance of general obligation bonds to finance construction of the network, and CFU is on track to pay off all long-term debt by the end of 2011, five years ahead of schedule In response to customer demand, additional bonds were issued to finance network expansion Those bonds are also being repaid with subscription revenues CFU could be generating a significant profit, but being a public utility, it has opted to return most of its profits to its households in the form of lower rates Cedar Falls residents pay $2 million less each year on cable and Internet access than the statewide average.55 The community has also received services they would not otherwise have had For example, CFU first offered high-speed Internet to businesses and residents in January 1997 The local cable company did not launch high-speed residential service until 2001, and highspeed business service in 2003 DSL was not widely available in 2004 CFU built its fiber plant to the city’s industrial park to attract businesses The private cable company has yet to extend its infrastructure there Since the fiber was installed, the industrial park has grown from 30 to 146 businesses, and employment from 1,400 to 4,300 people And since 2005, CFU Internet subscribers also have access to a wireless network in the downtown area Muscatine (Iowa) Water and Power (MWP) – Heartland Institute views MWP as a failure because it has raised cable rates to cover its costs Facts: In 1996, after learning that incumbents TCI and U.S West (now Qwest) had no plans to bring broadband into the community, Muscatine’s business leaders recommended a municipal communications utility Voters in Muscatine overwhelmingly approved the utility in 1997, with 94 percent voting in favor Muscatine launched cable television service in March 1999, and Internet service later that year Despite predatory pricing and other anticompetitive behavior by the incumbent cable operator,1 Muscatine Power and Water successfully maintained its customer base by 53 Paul Miller, “Bristol’s broadband push,” Virginia Business Magazine, November 2006 Ronald J Rizzuto, Iowa Municipal Communications Systems: The Financial Track Record, Heartland Institute, September 10, 2005 55 CFU charges $34.50 per month for a 70-channel cable television package It charges $40 per month for Mbps Internet connections, compared to a state average of $50 All Internet subscribers also have access to the downtown Cedar Falls wireless network It charges $69.50 per month for high-speed Internet and 70 channels of television, compared to a statewide average of $90 Businesses can get 10 Mbps connections for $80 to $150 per month, depending on the number of users 54 846 All Internet is Local providing higher quality services, including video on demand and wireless Internet access In January 2003, the public utility bought the incumbent’s (then Mediacom) assets in Muscatine and neighboring Fruitland The municipal utility has indeed raised its rates, but they remain below those of private providers elsewhere in the state.56 iProvo, Provo, Utah – The Reason Foundation calls this citywide fiber-to-the-premises network a failure because it has posted negative income in its first 18 months of operation Facts: Fiber-to-the-premises requires a very large up front investment, and takes time to build, but the network will last for at least 20 years It is normal to project losses for the first several years, during construction and while the customer base is built This is equally true for the private sector Verizon began offering its much publicized FiOS service in 2005, and expects to lose money on the investment until 2009 Provo also had unexpected expenses Like most networks built by public power utilities, the backbone of Provo’s network was built to connect electrical substations, allowing for improved monitoring of the electrical grid In 2001, the Utah legislature passed a bill making it possible for cities to build their own networks and sell wholesale access to private service providers But the bill also imposed restrictions on the use of general or enterprise funds Provo had used $2.3 million in power reserves to fund its network The law was applied retroactively, and the city was given 10 months to repay the fund Finally, Provo made a single company, HomeNet, exclusive provider when the network was launched After failing to meet subscription targets for a year, the company asked to be released from its contract and then filed for bankruptcy In July 2005, the city added two new service providers and began meeting subscription targets, and is now on track to achieve its original goal of 10,000 subscribers in early-2007, and to begin breaking even sometime in 2008 The network is not just for residential service It also provides 100 Mbps connections to Provo’s city buildings, fire stations, and schools, and improved reliability of the power grid In the coming years, iProvo’s fiber to the premises network can offer services the cable and phone networks are not capable of, such as distance learning courses with fullscreen interactive video 56 City of Iowa City Cable TV Division, Frequently Asked Questions Epilogue “Epilogue” – it sounds like the story is ending But obviously the Wi-Fi story is continuing strong, evidenced by the contents of this book So let us consider this as not an “epilogue”, but as just a brief pause to catch our breath This book has covered so many of the topics that we know are important today But based on our past experience, who really knows what future applications will be dreamed up? Who really knows which new technologies will prove to be important in the future evolution of Wi-Fi? It is very humbling to recall that back in the early and mid-1990s, when the IEEE 802.11 standards were originally being developed, the primary application on the minds of the key participants was not networking in the home, or wireless Internet access, or public hotspots, or voice over IP, or multimedia services, or city-wide wireless – but things like wireless bar code scanning and retail store inventory management These “vertical” applications for Wi-Fi technology continue to be important today, but oh how far we have travelled So only an actual seer could predict the real future of Wi-Fi over the next 10 years But one thing is clear: Wi-Fi will continue to play a role in our lives Everything in technology has a finite lifespan – hardware products have a lifespan, software products have a lifespan – but the lifespan of a successful protocol, implemented in millions of devices worldwide, can be very, very long Just consider TCP/IP, originally developed over 30 years ago, and we still use it every day each time we access the Internet Wi-Fi has reached that level of universal, global presence that undoubtedly ensures it a long and healthy life The ability of Wi-Fi technology to expand in so many directions while maintaining backwards compatibility has been one key to its success – most obviously in the data rate leaping from megabits to 11 to 54 to the hundreds of megabits possible with 802.11n – and the technology will certainly continue to evolve This book has hopefully given you some insights into where we have been and where we may be headed Of course, no one knows for sure – but it will certainly be a future with Wi-Fi, involving applications and technologies beyond anyone’s dreams today Greg Ennis Technical Director Wi-Fi Alliance Index 802.1d 41,86,347 802.1x 21,134,137,151,337,595 802.11a 1,25,181,224,318,539,609 802.11b 1,25,66,220,318,539,609,695 802.11d 25 802.11e 39,63,338,367 802.11g 1,25,181,228,318,539,551,695 802.11h 25,609 802.11i 20,135 802.11j 25 802.11k 6,517 802.11n 4,14,153,179,351,501,547 802.11p 7,245 802.11r 8,154,247 802.11s 8,57,154,249,342 802.11T 802.11u 10 802.11v 10 802.11w 11,157 802.11y 11,351 802.15.3 768 802.15.4 488,725 802.16d 618 802.16e 618 802.16h 478 802.19 480 802.22 491 3G 331,805 3GPP 354,430,446 3GPP2 353,446 4G 441,814 1xEV-DO 419,572,805 1xRTT 418 Access Category (AC) Access Control 289,611 Access Point (AP) 16,40,146,247,285,523 Accounting 355,443,596 Acknowledgement (ACK) 24,520 Adaptive Frequency Hopping (AFH) 470,512 Ad-hoc On-Demand Distance Vector (AODV) 241,334,650 Adjacent Channel Interference (ACI) 31 Admission Control 49 Advanced Encryption Standard (AES) 21,49, 137,149 Advanced Television Standards Committee (ATSC) 496 Aggregators 626 Analog-to-Digital Converter (ADC) 552 Angle of Arrival 664 Anomaly Analysis 171 Antenna Design 563,818 Antenna Q 567 Application Layer Gateway (ALG) 376 Arbitration Interframe Space (AIFS) 45,86,92, 333 Association 18,154,358 Attenuation 541 Authentication 18,151,265,284,355,443,595,607 Authenticator 150 Authorization 265,284,355,443,596 Automatic Power Save Delivery (APSD) 52 Basic Service Set (BSS) 17,285,522 Beamforming 2,188,197 Billing 599 Binary Convolutional Code (BCC) 186 Bit Error Rate (BER) 106,725 Block Acknowledgment (BA) Bluetooth 89,340,351,480,501,635 Bootstrapping 433 Box Chart 580,582,585 Breakout Gateway Control Function (BGCF) 446 Broadcast Integrity Protocol (BIP) 11 BSSID 33,524 Call Session Control Function (CSCF) 357 Captive Portal 590 CCMP 21,139,146 Cell ID 665 Channel Binding Channel Estimation 772 Channel State Information (CSI) 196 850 Index Cholesky Decomposition 211 Chu-Harrington Limit 567 Clear Channel Assessment (CCA) 22,476,520 Clear-to-Send (CTS) 65,292,542 Coexistence 479,501 Cognitive Radio 785,819 Cognitive WLAN 523 Communications Assistance for Law Enforcement Act (CALEA) 605,624 Complementary Code Keying (CCK) 28,551 Conductor Area 565 Confidentiality 19 Congestion Control 338 Contention Window (CW) 42,64,333 Context-Aware Service Management 671 Cordless Telephones 479 Correlated Mesh Data Protocol 311 Coupling Architecture 442,444,445 Cross-layer Video Streaming 107 CSMA/CA 22,41,64,287,320,473,637 CSMA/CD 22 Cyclic Delay Diversity (CDD) 184 DCF Interframe Space (DIFS) 40,64 Dead Peer Detection 385 Dead Spots 546 Deauthentication 18 Dedicated Short Range Communications (DSRC) 7,245 Denial of Service (DoS) 174,269,621 Diameter 433 Diffie-Hellman 372 Digital Millennium Copyright Act (DMCA) 622 Digital-to-Analog Converter (DAC) 552 Direct Sequence Spread Spectrum (DSSS) 27, 474,551 Disassociation 18,152,360 Discovery 18,336,343 Disruption Tolerant Transport 651 Distributed Co-ordination Function (DCF) 22, 65,67 Distribution System (DS) 17 Diversity Architectures 578 Domain Name Service (DNS) 619,685 Domain Registration 401 Dual Carrier Modulation (DCM) 760 Dual-Mode Phones 631 Duplicate Addresses Detection (DAD) 253 Dynamic Channel Selection (DCS) 478 Dynamic Frequency Selection (DFS) 471 Dynamic Host Configuration Protocol (DHCP) 17,252,300,369,530,594,685 Dynamic Source Routing (DSR) 695 Dynamic Spectrum Access 491 EAP-AKA 151,430 EAP-MD5 152 EAP over LAN (EAPOL) 21 EAP-SIM 151,430 EAP-TLS 137,151 EAP-TTLS 152 EDGE 417 Encoding and Data Rates 27 Encryption 20,132 Enhanced Distributed Channel Access (EDCA) 40,86,333,367 Error Vector Magnitude (EVM) 559 ESSID 33,283 Extended Service Set (ESS) 17,249,522 Extensible Authentication Protocol (EAP) 21, 134,283,369 Fairness 338 Federal Information Processing Standard (FIPS) 150 Fixed Mobile Convergence (FMC) 811 Forwarding 337 Free Space Optics (FSO) 785 Frequency Agility 322 Frequency Division Duplex (FDD) 477 Frequency Domain Spreading (FDS) 761 Frequency Hopping Spread Spectrum (FHSS) 474 Fuzzing 159 Generic Authentication Architecture (GAA) 433 Geometric Analysis 502 GIS 629 Global Positioning Satellite (GPS) 240,572,743 GPRS 417,430,441,680 Green Field (GF) Group Master Key (GMK) 139 Groupwise Transient Key (GTK) 22,139 GSM 151,356,417,430,441 Guard Interval (GI) 3,181,205,756 Handoff 340,354,405,459 HCF Controlled Channel Access (HCCA) 46,86, 106,367 Hidden Node 542 High Rate Packet Data (HRPD) 354 High-Speed Packet Access (HSPA) 572,805 Index 851 High Throughput (HT) 1,153,509 Home Location Register (HLR) 354,812 Home Networking 245 Home Subscriber Server (HSS) 430,446 Host Identity Payload (HIP) 431 Hotlining 604 Hotspots 589,609,625,789 HT Long Training Field (HT-LTF) 183 HT Short Training Field (HT-STF) 183 HT Signal Field (HT-SIG) 183 Hybrid Coordination Function (HCF) 86,106 Hybrid Wireless Mesh Protocol (HWMP) 9,335 Independent Basic Service Set (IBSS) 16,63,249, 518 Industrial, Scientific and Medical (ISM) 469,539 Information Element (IE) 157 Infrared (IR) 475,785 Initialization Vector (IV) 22,133,147 Injection Tier Design 297 Integrity Check Validation (ICV) 168 Intelligent Transportation Systems (ITS) Inter-Symbol Interference (ISI) 756 Interworking 351,429,441 Intrusion Detection and Prevention (IDP) 270 IP Multimedia Subsystem (IMS) 354,446,813 IPSec 358,432,617 Legacy Signal Field (L-SIG) 183 List Sphere Decoding (LSD) 203 Long Term Evolution (LTE) 805 Low Density Parity Check (LDPC) 3,183,204, 728 MAC Protocol Data Unit (MPDU) 64,154,188, 501 MAC Service Data Unit (MSDU) 44,64,110,154, 188,501 Management Control Packets 29 Management Frames (MF) 11 Master Key (MK) 139,150 Media Gateway Control Function (MGCF) 354 Media Independent Handover (MIH) 10 Media Resource Function (MRF) 446 Medium Access Control (MAC) 24,42,63,188, 249,333,348.474,552,637,730 Mesh Access Point (MAP) 343 Mesh Key Distributor (MKD) 155 Mesh Networks 57,109,114,217,239,263,293, 307,317,329,699 Mesh Point (MP) 343 Mesh Point Portal (MPP) 343 Message Integrity Code (MIC) 21,139,149 Meter Reading 275 MIMO 1,193,474,503,548,783 MIMO-OFDM 189,193,501 MISO 196 Mixed-Mode Preamble 181 MMSE 187,211,505,766 MOBIKE 399,432 Mobile Ad-hoc Network (MANET) 214,301, 329,642,697 Modulation and Coding Scheme (MCS) 180, 194,489,503 Multiband OFDM Approach (MBOA) 733,749 Multicasting 250 Multipath 540,752 Multi-Purpose Access 615 Multi-Tier Network Design 285 Municipal Wi-Fi 617,813 Network Address and Port Translators (NAPT) 435 Network Address Translation (NAT) 376,422, 435 Network Allocation Vector (NAV) 65,174 Network Application Function (NAF) 433 Network Interface Card (NIC) 24,612 Network Localized Mobility Management 368 Network Management 32,255,341 Network Monitoring 599 Network Operations Center (NOC) 284,593,601, 684 Next Generation Network (NGN) 431 Nonce 22,148 Object Identifier (OID) 7,517 Operations Support Systems (OSS) 592,601 Optimized Link State Routing Protocol (OLSR) 241,302,334,650 Orthogonal Frequency Division Multiplexing (OFDM) 27,179,193,474,725,762 Orthogonal Frequency Division Multiple Access (OFDMA) 477,820 Over-the-Air Service 678,681 Packet Binary Convolutional Coding (PBCC) 28 Packet Data Gateway (PDG) 357,430 Packet Data Interworking Function (PDIF) 357, 369 Packet Data Protocol (PDP) 433 Packet Error Rate (PER) 480,502 852 Index Packet Structure and Type 28 Pair-wise Master Key (PMK) 22,139 Pair-wise Transient Key (PTK) 22 PCF Interframe Space (PIFS) 40,66 Peer Link Establishment 336,344 Peer-to-Peer Applications 622,815 Per-Hop Behavior (PHB) 254 Phishing 619 PHY Service Data Unit (PSDU) 757 Physical Layer Convergence Protocol (PLCP) 28,67,757 PLCP Protocol Data Unit (PPDU) 757 PMK Caching 140 Point Coordination Function (PCF) 22,40,64,452 Polled Channel Access 46 Port Isolation 621 Power Management 51 Pre-Authentication 141 Predictive Wireless Routing Protocol (PWRP) 309 Pre-Shared Key (PSK) 18,133 Public Safety 242,271 Q-Volume Space 569 Quality of Service (QoS) 9,39,86,105,254,524, 597,730 Radar 743 Radiation Efficiency 566 Radiation Resistance 566 Radio Access Network (RAN) 444 Radio Frequencies and Channels 24,249 Radio Resource Measurement (RRM) 6,518 Rayleigh Channel 576 RC4 21,139 RCPI 519 Real-Time Location System (RTLS) 662 Reassociation 18 Received Signal Strength Indicator (RSSI) 27, 365,502,537,668 Reduced Interframe Space (RIFS) 4,188 Remote Access Dial-In User Service (RADIUS) 21,137,153,265,598,613 Request-to-Send (RTS) 22,65,292,520,542 RF Identification (RFID) 662,743 Rician Channel 581 Roaming 17,136,140,253,298,310,388,613,627 Robust Security Network Association (RSNA) 11 Role-Based Access 175 Routing 30,309,310,337,345 Saturation Throughput 69 Scanning Process 361 Secure Sockets Layer (SSL) 603 Security 19,34,131,251,336,344,433,606 Sensor Networks 633 Service Level Agreement (SLA) 598 Service Management 592 Service Set ID (SSID) 33,362,524,597,612 Session Initiation Protocol (SIP) 378,446 Short Interframe Space (SIFS) 40,65 Short Training Field (STF) 182 Signal to Interference Ratio (SIR) 483,505 Signal to Noise Ratio (SNR) 27,114,204,294, 502,543,637 Signature Analysis 168 Simple Network Management Protocol (SNMP) 255,521,601 SISO 197 Site Surveys 546 Snorting 621 Space Time Block Coding (STBC) 3,187 Spatial Spreading 196 Spectrum Management 309 Splash Page 603,612 Supplicant 152 Symbol Error Rate (SER) 483 System on Chip (SoC) 551 Television Frequency Bands 473 Temporal Analysis 507 Temporal Key Integrity Protocol (TKIP) 21,133, 139,146 Tiered Contention Multiple Access (TCMA) 45 Time Division Duplex (TDD) 197,477 Time Domain Spreading (TDS) 761 Time Frequency Codes 754 Topologies 16 Topology Broadcast with Reverse Path Forwarding (TBRPF) 241 Tracking 661 Traffic Indication Map (TIM) 52,367 Transmission Opportunity (TXOP) 6,41,88, 114, 507 Transmit Power Control (TPC) 471 Traffic Specification (TSPEC) 47 Trend Analysis 170 Triangulation-based Approaches 666 Tunnel Inner Address (TIA) 433 Tunnel Procedures 369,381 Ultra Mobile Broadband (UMB) 805 Index 853 Ultra-Wideband (UWB) 351,476,719,749 Uncoordinated Coexistence Protocol (UCP) 478 U-NII Frequency Bands 26,449 Universal Access Method 628 Universal Mobile Telecommunication System (UMTS) 418,441,687 Universal Serial Bus (USB) 749 Unlicensed Frequency Bands 469 Unlicensed Mobile Access (UMA) 431 Unmanned Aircraft 695 Video Surveillance 245,272 Virtual LAN 601 Virtual Network Operators 601,607 Virtual Partitioning 603 Virtual Private Network (VPN) 146,274,283, 589,613 Viterbi Decoding 201,212,775,780 Voice Call Continuity (VCC) 352,387,397 Voice over IP (VoIP) 8,139,275,298,317,339, 352,423,431,518,524,597,630,682,798,807 VSWR 572 Wall Garden 603,628 Web Filtering 269 Wideband CDMA (WCDMA) 434 Wi-Fi Alliance 14,132,146,789 Wi-Fi Protected Access (WPA) 8,20,132,135, 137,610 Wi-Fi Protected Set-up (WPS) 146 Wi-Max 225,247,288,325,331,351,489,572, 607,618,815 WiMedia 753,754 Wired Equivalent Privacy (WEP) 18,132,146, 610 Wireless Access Gateway (WAG) 357 Wireless Access for Vehicular Environment (WAVE) Wireless Information Service Provider (WISP) 518,597 Wireless Intrusion Detection 146,166 Wireless Local Area Network (WLAN) 13 Wireless Network Analysis 29 Wireless Personal Area Network (WPAN) 749 Wireless Regional Area Network (WRAN) 478 WISPr 629 WLAN Administration 34 WLAN Physical Layer 1,24,474 WLAN Regulation 15 WLAN Troubleshooting 36 Zigbee 476,634 ... page intentionally left blank Emerging Technologies in Wireless LANs Wireless LANs have become mainstream over the last few years What started out as cable replacement for static desktops in indoor... São Paulo Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www .cambridge. org Information... interests are in QoS, security, performance and throughput, meshing and internetworking, management and design, or just the latest in Wi-Fi applications, you will find an indepth discussion inside