List of Figures

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Chapter 1: What is Wi-Fi

Figure 1.1: The Wi-Fi Alliance's Wi-Fi Certified Trademark. Products bearing this trademark have been certified by the Wi-Fi Alliance as meeting its interoperability standards
Figure 1.2: The Wi-Fi Alliance's Wi-Fi Zone brand.

Chapter 2: The Promise of Wi-Fi

Figure 2.1: Per industry study conducted by NOP World Technology on behalf of Cisco, Inc. Graphic courtesy of NOP World Technology.
Figure 2.2: Per industry study conducted by NOP World Technology on behalf of Cisco, Inc. Graphic courtesy of NOP World Technology.
Figure 2.3: It costs less to support a productive worker on a WLAN than on other popular mobile devices.
Figure 2.4: In a mesh network, each wireless node serves as both an access point and wireless router, creating multiple pathways for the wireless signal. Mesh networks have no single point of failure and can be designed to route around line-of-sight obstacles that can interfere with other wireless network topologies. (Graphic courtesy of Proxicast.)

Chapter 3: Fueling the Wi-Fi Fire

Figure 3.1: Subscriber Identification Modules (SIMs) could play an important role in expanding Wi-Fi's acceptance.
Figure 3.2: A smart card consists of a piece of plastic similar in size to a credit card. Embedded in it is a tiny computer microprocessor and memory chip(s), such as a SIM.
Figure 3.3: A silicon chip is a tiny electronic circuit on a piece of silicon crystal. It contains hundreds of thousands of micro-miniature electronic circuit components, which are packed and interconnected in multiple layers within a single chip. Then the surface of the chip is overlaid with a grid of metallic contacts used to wire the chip to other electronic devices. And all of this is done in an area less than 2.5 millimeters square. (There are 2.54 centimeters to an inch, and each centimeter is 10 millimeters long.) These components can perform control, logic, and memory functions. Silicon chips are found in the printed circuits of, for example, personal computers, televisions, automobiles, appliances, etc.
Figure 3.4: Vocera Communications Network Diagram. Graphic courtesy of Vocera Communications.
Figure 3.5: The badge on the right shows the speaker and the badge on the left displays the LCD screen.

Chapter 4: The Regulators' Role

Figure 4.1: The electromagnetic spectrum. While this book deals with wireless data transmission, and this section discusses spectrum within that connotation, the reader should understand that "spectrum" is a general term that is used to encompass both the spatial and temporal properties of any medium, including your telco's copper wiring, fiber optic cable, coaxial cable, and ambient air.
Figure 4.2: The "Radio Frequencies" within the Electromagnetic Spectrum.

Chapter 5: Modulation Techniques

Figure 5.1: A spread spectrum signal wave.
Figure 5.2: Direct Sequence Spread Spectrum.
Figure 5.3: Spread Spectrum using the frequency hopping technique.
Figure 5.4: This graphic shows how the CCK modulation is formed. Graphic courtesy of Intersil.
Figure 5.5: The orthogonal nature of OFDM's efficient use of bandwidth.

Chapter 6: The Wi-Fi Standards Spelled Out

Figure 6.1: The OSI model in relation to the IEEE's 802.11 specifications.
Figure 6.2: 802.11a's OFDM operating bands, channels, transmit frequencies and maximum output power. The low and middle bands are intended for in-building applications, and the high band for outdoor use (e.g., building-to-building).
Figure 6.3: 802.11a sub-channels.
Figure 6.4: 802.11a independent clear channels.
Figure 6.5: Parameters for 802.11a transmission rates.
Figure 6.6: This graphic illustrates the frame format for an 802.11a frame.
Figure 6.7: Modulation techniques of OFDM as used in 802.11a.
Figure 6.8: Constellation map for the 16-QAM 802.11a modulation.
Figure 6.9: Although HiperLan/2 has lain dormant since its ratification, its predecessor has had some success outside the U.S.
Figure 6.10: The IEEE 802.11 PHY frame using DSSS.
Figure 6.11: 802.11b contention window.
Figure 6.12: The hidden node problem. Workstations A, B and C can all see wireless access point P. Workstations A and B can see one another, and B and C can see one another, but A can't see C.
Figure 6.13: 802.11g modulation schemes and corresponding data rates.
Figure 6.14: 802.11g is a PHY extension to the 802.11b standard, although there are many differences between the two. For instance, 802.11g differs in packet format. While the only mandatory modes are CCK for backward compatibility with existing 11b radios and OFDM for higher data rates, developers can choose two optional elements, CCK/OFDM and packet binary convolutional coding (PBCC).
Figure 6.15: This graphic shows the difference in CCK and OFDM modulated waveforms.
Figure 6.16: 802.1X state before (left) and after (right) successful mutual authentication.
Figure 6.17: MPDU format after TKIP encryption.
Figure 6.18: This graphic depicts the TKIP encapsulation process.
Figure 6.19: Format of a CCMP encrypted MPDU. The packet is expanded by 16 bytes over an unencrypted frame, and is identical to a TKIP frame, with the exception of the legacy WEP ICV included in a TKIP frame.
Figure 6.20: Diagram of the CCMP encapsulation process.

Chapter 7: A WLAN Primer

Figure 7.1: Technical differences between 802.11a and 802.11b.
Figure 7.2: Speed comparisons of various connectivity technologies.
Figure 7.3: For bit error rates less than or equal to 1e-5, the 802.11a standard specifies minimum receiver sensitivity with and without adjacent-channel interference (ACI).
Figure 7.4: For bit error rates less than or equal to 1e-5, there are defined minimum signal-to-noise ratios for 802.1b and 802.1a that will allow the required data rates to be met.
Figure 7.5: A general view of the 5 GHz worldwide spectrum allocation and authorized transmit power as of 4/01/02.
Figure 7.6: The international regulatory standards to which all 802.11 devices must adhere.
Figure 7.7: The various Basic Service Set (BSS) modes that can be deployed in a wireless networking environment.
Figure 7.8: A WDS bridge setup.
Figure 7.9: A WDS can have forwarding functionality by setting up APs as repeaters.
Figure 7.10: The three access points on the right hand side of this graphic are connected by Ethernet cable and hence use a wired Distribution System, while the four access points to the left are wirelessly connected, and are said to use a Wireless Distribution System. Graphic courtesy of Agere Systems, Inc.
Figure 7.11: A typical corporate network architecture that uses both wired and wireless networking technologies.
Figure 7.12: Various solutions have been proposed to solve the problem of seamless continuity of IP sessions and applications. They can be classified according to the layer of the OSI model at which they are implemented.
Figure 7.13: Graphic A and B depict how mobility for IPv4 works, whereas Graphic C depicts mobility for Ipv6.

Chapter 8: A Practical WLAN Deployment Plan

Figure 8.1: Relative attenuation of RF Obstacles. The ability of radio waves to transmit and receive information, as well as the speed of transmission, is affected by the nature of any obstructions in the signal path. This table shows the relative degree of attenuation for common obstructions. Graphic Courtesy of Intel Corp.
Figure 8.2: Example of an "outside in" survey method. This method helps to ensure that the WLAN's coverage area doesn't extend needlessly beyond the physical plant. Graphic Courtesy of Cisco Systems, Inc.
Figure 8.3: User segmentation without wireless VLANs. Graphic courtesy of Cisco Systems, Inc.
Figure 8.4: An indoor wireless VLAN deployment where four wireless VLANs are provisioned across a campus to provide WLAN access to full-time employees (segmented into engineering, marketing, and human resources user groups) and guests. Graphic courtesy of Cisco Systems, Inc.
Figure 8.5: An outdoor wireless VLAN deployment scenario. Wireless trunking connects the root bridge to the non-root bridges. The root and non-root bridges terminate the 802.1Q trunk and participate in the Spanning-Tree Protocol process of bridging the networks together. Graphic courtesy of Cisco Systems, Inc.

Chapter 9: Bridging Buildings

Figure 9.1: Point-to-Point Bridging.
Figure 9.2: An example of how a building-to-building bridge might be used.
Figure 9.3: As this graphic shows, you needn't limit the bridge to only two buildings.
Figure 9.4: FCC Regulations for 2.4 and 5 GHZ unlicensed radio bands. (In Europe, the ETSI is the regulatory body that regulates the Antenna/Radio power output and system range).
Figure 9.5: In late 2002, Network Computing magazine tested a group of 5 GHz Ethernet bridges. This chart lays out the results of those tests. The underlying radios and modulation systems varied considerably from product to product. In most cases, it's a trade-off between price and performance. Packing more bits into each clock cycle requires more sophisticated radio technology—and you'll pay for that luxury. Because regulations vary by sub-band at 5 GHz, you'll get longer range from products that operate in the 5.8-GHz UNII-3 sub-band.
Figure 9.6: When designing an outdoor wireless link, the Fresnel zone, which is the elliptical area immediately surrounding the visual path as shown in this graphic, must be taken into account. Typically, 20% Fresnel Zone blockage introduces little signal loss to the link. Beyond 40% blockage, signal loss will become significant. The Freznel zone will vary depending on the length of the signal path and the frequency of the signal, although the radius of the Fresnel Zone at its widest point can be calculated by the above formula, where d is the link distance in miles, f is the frequency in GHz, and r is the radius off of the center line of the link in feet. Note that this calculation is based on a flat earth, i.e. it does not take the curvature of the earth into consideration. The effect of this is to budge the earth in the middle of the link. Thus for long links have a path analysis performed that takes the earth's curvature and the topography of the terrain into account.

Chapter 10: Contrasting Deployments

Figure 10.1: In an 802.11b network of three cells, one of the three cells (Cell 3) experiences adjacent-channel interference (ACI) from the other two cells because the 11b standard provides for only three frequency channels.
Figure 10.2: For an 8-cell 802.11a network, which allows for 54 Mbps operation, the greatest interference is experienced by a station belonging to Cell 4 located at Vertex G.
Figure 10.3: In an 8-cell 802.11b configuration, the least signal-to-noise ratio experienced by any station in the network is about 7.45133 dB, allowing for full 11 Mbps data transfer rate.
Figure 10.4: Coverage Comparison of 802.11b and 802.11a. There are significant differences between 11a and 11b in terms of each standard's achievable communication range between the access point and the computing device, and the corresponding service coverage area.
Figure 10.5: Three non-overlapping 802.11b-based networks in the 2.4 GHz band.
Figure 10.6: Twelve 802.11a networks in the U.S. 5 GHz band.
Figure 10.7: Comparative free space path loss between 2.4 GHz and 5 GHz systems.
Figure 10.8: The effect of a roaming client is similar for both the 802.11b a) scenario, and b) scenario. The AP will alternate transmissions between Client 1 and Client 2, and network throughput will drop between 70 and 77 percent.
Figure 10.9: When two clients (computing devices) are close to an AP (a), the data rates are similar. But, as Client 1 roams to the network edge (b), its rate drops quickly, slowing considerably the time taken for the packet transmit and ACK.
Figure 10.10: 802.11g-only networks (a) can hit 30 Mbps throughput. But, when a legacy 802.11b client is introduced (b), protection mechanisms kick in. Still, the WLAN's throughput will drop to 9.3 Mbps (including TCP/IP).
Figure 10.11: In a mixed 11g/b environment, the throughput (including TCP/IP overhead) depends on the number and type of clients associated with the access point. The figures represent total network throughput.
Figure 10.12: For mixed-mode upstream traffic, the 802.11g client will get twice as many transmit opportunities because its back-off counter is statistically set to a lower number. This doubles the upstream data rate.
Figure 10.13: Approximate spectral placement of 802.11b channels.
Figure 10.14: This figure shows an 802.11b overlapping cell arrangement using non-overlapping radio channels 1, 6 and 11.
Figure 10.15: Microcell design with interface from a single high-power client.

Chapter 11: The WISP Industry

Figure 11.1: This graphic depicts the four layers within the WISP industry. As in the ISP space, the most successful companies will focus primarily on one industry layer, partner between the layers, and compete within their own layer. Graphic courtesy of Boingo Wireless Inc.
Figure 11.2: An example of a typical do-it-yourself HotSpot.
Figure 11.3: Example of a HotSpot deployed by a HotSpot operator using a wireless access controller. In this instance it is Colubris Networks' CN3000 Wireless Access Controller, which is designed for small to medium HotSpots, such as an Internet café or a small hotel. The functionality included in the CN3000 provides, among other things, access point capabilities, a full router, a customizable firewall, a RADIUS AAA (Authentication, Authorization, and Accounting) client, customizable login pages, per session per user access lists, an embedded VPN client for secure remote manageability, directed traffic to ensure the integrity of the HotSpot operator's back-office Network Operating Center (NOC), and more.
Figure 11.4: A Cafe.com venue owner's HotSpot network would look something like this.
Figure 11.5: When a HotSpot operator enters into bilateral agreements, it must have the wherewithal to adequately handle all of the back-end tasks.
Figure 11.6: When a HotSpot operator partners with an aggregator, the aggregator takes on most of the back-office chores.
Figure 11.7: Anatomy of a HotSpot from GRIC Communication's point of view. Graphic courtesy of GRIC Communications.
Figure 11.8: Cellular carriers can establish partnerships with members of the WISP industry to market their services. This graphic depicts a cellular HotSpot operator that chooses to not deploy its own access network. Rather, it buys capacity from networks deployed by others through the services of an aggregator, although it does manage its own customer relationships and billing (i.e. the end-users pay the cellular provider for HotSpot usage).
Figure 11.9: The brand charges its end-user and pays the aggregator fees for network aggregation, roaming, settlement, support, and software. The aggregator in turn settles with the HotSpot operators, paying a wholesale connect fee for each of the brand's user connections.
Figure 11.10: This shows the choices available to HotSpot operators who want to provide their end-users with an ever-wider coverage area, but are unwilling to go through an aggregator. Both options require the operator to build and maintain extensive back-office systems. But perhaps the bilateral roaming model presents the most challenges. Roaming end-users demand the same user experience no matter which network they are using. To provide such uniform experience, however, requires that the roaming partners harmonize their operations, e.g. AAA, assess management, service provisioning, content, billing, and end-user assistance.
Figure 11.11: The challenges to offering bilateral roaming—harmonization of operations is essential to providing end-users with a successful roaming experience.
Figure 11.12: Aggregators are best suited to handle the legal, administrative, technical and services issues that arise during multilateral roaming partnerships.

Chapter 12: Building a Hotspot

Figure 12.1: FatPoint allows a HotSpot operator to design a custom login screen that enables the venue or operator to brand the first screen subscribers see with news, special offers and up-and-coming events. Graphic Courtesy of FatPort.
Figure 12.2
Figure 12.3: A "homegrown" Hotspot network layout. There are any number of ways a HotSpot can be designed and constructed. The one shown in this graphic is the minimum. Note that some vendors combine one or more of the standalone devices shown here into multipurpose units.

Chapter 13: Wi-Fi and Cellular—A Dynamic Duo

Figure 13.1: How a call traverses a cellular network. Each hexagon represents a "cell" which is served by an antenna (radio/cell tower) and base transceiver station.
Figure 13.2: GSM is the 2G technology of choice, but in North America it's more muddled with a mix of TDMA, CDMA and GSM being used for 2G cellular communications.
Figure 13.3: Official IMT 2000 recognized 3G transmission standards.
Figure 13.4: Comparing Wi-Fi and 3G.

Chapter 14: Wi-Fi in the Corporate World

Figure 14.1: This graphic gives an indication of the infrastructure start-up costs for three potential WLAN deployments— large (800 users), medium (150 users), and small (32 users). Intel IT's calculations include the initial hardware, software, and labor expenses to build the WLAN, but they do not include sustaining costs for supporting a WLAN over time. (But those costs must be accounted for when calculating ROI.) From Intel Information Technology's May 2001 white paper entitled "Wireless LANs." Graphic courtesy of Intel.
Figure 14.2: Timesavings equal productivity. These tables represent the Intel IT WLAN pilot project's calculations. The top table shows the user-perceived timesavings and the adjustments thereto. The bottom table shows the resulting translation of the timesavings into annual WLAN productivity gains. This was done by taking the daily timesavings for productivity gains (last column of the first table), calculating the value of each end-user's productivity gains, then multiplying each end-user group's average hourly burden rate-salary plus benefits-by the number of workdays per year (235). Graphic courtesy of Intel.

Chapter 15: Vertical WLANs

Figure 15.1: St. Luke's WLAN. The mobility software is deployed on a proxy server and individual mobile computing devices. The proxy server brokers IP addresses for the client computing devices, maintains network and applications sessions, and acts as a firewall between the wired and wireless networks. Graphic courtesy of NetMotion Wireless Inc.
Figure 15.2: Percentage of educational IT managers who perceived benefits from wireless LAN technology. Graphic courtesy of Cisco Systems.
Figure 15.3: The Vernier Networks System includes a Control Server, which manages access rights for the entire network, and Access Managers that monitor, secure, and control traffic flowing through access points. Graphic Courtesy of Vernier Networks.

Chapter 16: Providing Quality of Service

Figure 16.1: TCP/IP stack as it relates to the Layers of the TCP/IP Network Model (note that this model has fewer layers than the ISO/OSI Reference Model, but they encompass the same things).
Figure 16.2: DiffServ can limit the rate of the WLAN's traffic sources in order to support the network's QoS needs. It does this by dividing traffic into three service categories— BE (Best Effort), AF (Assured Forwarding), and EF (Expedited Forwarding). BE and AF traffic is forwarded using WFQ (Weighted Fair Queuing), and EF traffic is forwarded using PQ (Priority Queuing).
Figure 16.3: End-to-end Quality of Service (QoS) network structures.
Figure 16.4: How the 802.11 MAC's basic mechanism is being enhanced in 802.11e to provide QoS.
Figure 16.5: A typical end-to-end DiffServ architecture. A DiffServ edge router handles the classification, metering, and marking of the packets, while the core routers take care of queue management, scheduling, and traffic shaping.
Figure 16.6: This diagram illustrates the different QoS methods that can be applied at different layers of communication and aggregation points.
Figure 16.7: In VoWLAN systems, the UDP protocol sits on both the MAC and PHY layers.
Figure 16.8: This diagram illustrates Wi-Fi's RTS and CTS mechanisms.

Chapter 17: Dealing with Security Issues

Figure 17.1: A WLAN with a VPN that uses IPsec in addition to WEP.
Figure 17.2: An example of a wireless network with a "VPN overlay."

Chapter 18: The Access Point

Figure 18.1: In most WLANs, access points act as isolated systems providing 802.11 functions, but when you add a wireless switch to the mix, many of the APs functions are taken over by the switch, allowing the AP to do what it does best, receiving and transmitting radio signals.
Figure 18.2: The Chantry BeaconWorks solution combined with its VNSWorks product allows a WLAN to create multiple virtual networks over a single WLAN infrastructure. Graphic courtesy of Chantry Networks.
Figure 18.3: The Cranite Systems' WirelessWall Software Suite consists of the WirelessWall Policy Server to support the creation of policies that control the characteristics of each wireless connection; WirelessWall Access Controller, to enforce policies for each wireless connection, to encrypt and decrypt authorized traffic, and to provide mobility services to users as they move across subnets throughout the network; and Cranite Client Software which operates on each mobile device accessing the network to terminate one end of a secure tunnel (the other end terminates at the Access Controller), and encrypt and decrypt data for that device's connection. Graphic courtesy of Cranite Systems.
Figure 18.4: This diagram depicts the Vernier Networks System, which consists of the CS 6000 Control Server as a centralized security configuration and management system, and the AM 6000 Access Manager as used in a network designed for Experio, a consulting firm with nearly 1000 employees and 16 offices across the U.S. The WLAN's architecture, as depicted in this graphic, provides centralized control over multi-site networks, and uses a two-tier architecture that can scale to support even the most distributed enterprise networks. Graphic courtesy of Vernier Networks.
Figure 18.5: The left graphic depicts whip antennae with a BNC connector. They provide quick-connect half turn, same as on the old 10base2 Ethernet cables. (In case you are wondering, BNC stands for "Bayonet Neill-Concelmann".) The right grapic depicts TNC connectors. These connectors are basicially just a threaded version of a BNC connector (ergo the "T" rather than the "B").

Chapter 19: The Antenna

Figure 19.1: Multiple signals combine in the RX antenna and receiver to cause distortion of the signal. There can be more than one path that RF takes when going from a TX (transmit power) to a RX (receiver sensitivity) antenna. Graphic courtesy of Cisco Systems.
Figure 19.2: Omni-directional antenna coverage pattern.
Figure 19.3: Examples of the beam coverage of a yagi antenna (left) and a patch antenna (right).
Figure 19.4: Dynamic diversity enables a higher link rate in more adverse channel conditions than is possible in conventional systems, while avoiding excessive overall power consumption by the transceiver/modem components.

Chapter 20: Client Devices

Figure 20.1: Some of the client computing devices that most commonly access the typical corporate WLAN.
Figure 20.2: Storage devices and more. This graphic depicts from left to right the Apple iPod MP3 player, Canon digital camera, Zip drive, HP CD Player, Labtec Web cam, Pocketec portable hard drive, Phillips Tivo device, and Toshiba's portable DVD player.
Figure 20.3: Printing wirelessly. This graphic depicts from left to right the HP Jetdirect 380x 802.11b wireless external print server, Zebra QL 320 direct thermal mobile printer, Epson Stylus C8OWN printer, Netgear PS111W 802.11b Wireless Ready Print Server, and the Buffalo AirStationTM Ethernet Converter (WLI-T1-S11G), which allows you to connect a network-ready Brother Printer/MFC to a Wi-Fi network in ad-hoc or infrastructure mode. Print servers help small workgroups to easily share a broad range of network-capable printers and multi-function peripherals across wireless networks.
Figure 20.4: This graphic depicts from left to right the C-Pen 800C Handheld Scanner (can scan directly into a cursor position on a PC), Konica Film Scanner for Professional RX-3, Trust SCSI Connect 19200 high resolution scanner (good for scanning graphics), and HP 3500c Scanjet color scanner.
Figure 20.5: This graphic depicts from left to right Intermec ScanPlus 1800 (barcode reader), passive RF tags that require no battery and are inexpensive and long lasting, Symbol Technologies SPT1700 handheld computer with barcode scanner, Panasonic Toughbook 01 ruggedized handheld computer, and Miltope TSC-750 ruggedized computer.
Figure 20.6: This graphic shows an Eten Smartphone P600. These devices can serve dual duty as both wireless phone and PDA.
Figure 20.1: Wireless network interface cards come in many different forms.

Chapter 21: Cabling, Connectors and Wiring

Figure 21.1: A pigtail cable, which is simply a small length of cable with adapting connectors to join a proprietary socket on a device to an external antenna cable.
Figure 21.2: Examples of low loss, weatherproof, and phase-stability coaxial antenna cables. All of the depicted cabling feature 50 Ohm impedance for connecting between access point and 2.4 GHz antenna.
Figure 21.3: An example of the various types of connectors you might need when deploying a WLAN.

Appendix I: The Open Systems Interconnection (OSI) Model

Figure A.1: The OSI Model.



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Going Wi-Fi. A Practical Guide to Planning and Building an 802.11 Network
Going Wi-Fi: A Practical Guide to Planning and Building an 802.11 Network
ISBN: 1578203015
EAN: 2147483647
Year: 2003
Pages: 273

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