CWNA Guide to Wireless Lans, Second Edition2-1

CWNA Guide to Wireless Lans, Second Edition2-1

CWNA Guide to Wireless LANs, Second Edition2-1

Chapter 2

Wireless LAN Devices and Standards

At a Glance

Instructor’s Manual Table of Contents
  • Overview
  • Objectives
  • Teaching Tips
  • Quick Quizzes
  • Class Discussion Topics
  • Additional Projects
  • Additional Resources
  • Key Terms

Lecture Notes

Overview

In this chapter, the students will look at wireless devices and the standards that help create and regulate them. The chapter begins by exploring the different types of unique wireless hardware that go into a wireless local area network (WLAN). Next, it describes the organizations that create WLAN standards as well as those bodies that regulate the standards. Finally, the students will learn about the wireless LAN standards themselves.

Chapter Objectives

  • List WLAN devices and describe their basic functions
  • Explain the different types of communication standards and why standards are important
  • List the three major wireless standards and regulatory agencies and their functions
  • Describe the different IEEE WLAN standards

Teaching Tips

WLAN Devices

  1. Provide an overview of WLAN devices. Mention that each wireless device has a counterpart found in a wired network.

Wireless Network Interface Card

  1. Explain the purpose and functionality of a NIC. Illustrate with Figure 2-1. If possible, pass a NIC around to the students.
  1. Explain that a wireless NIC performs the same functions as a wired NIC, except that it has no port for a wire connection to the network. Using the list on page 34 of the text as a guide, explain the steps that a wireless NIC performs when transmitting data.
  1. Discuss the various forms and styles of wireless NICs, illustrating with Figure 2-2. If possible, pass examples of each of these styles of wireless NIC around to the students.

Teaching

Tip / A standalone USB device has an advantage over a key fob because the standalone device can be repositioned to improve reception.
  1. Describe the types of wireless NICS available for laptops. Explain that mini PCIs were specifically developed for integrating communications peripherals such as modems and NICs onto a laptop computer. Illustrate with Figure 2-3. If possible, pass a CardBus wireless NIC around to the students.

Teaching

Tip / A CardBus card improves input/output speed over a PC Card by increasing the bus width to 32 bits yet still supports lower-voltage PC Cards.
  1. Discuss the various types of wireless NICS available for small mobile devices, such as PDAs. Illustrate a wireless CompactFlash card with Figure 2-4, and explain the concept of flash memory. If possible, pass one around to the students.
  1. Explain that there is a movement towards integrating wireless NICs onto processors, which would eliminate the need for external wireless NICS.
  1. Discuss the concept of a driver, explaining that a driver is necessary to interface the hardware with the operating system. Explain that, beginning with Windows XP, all Microsoft desktop operating systems recognize a wireless NIC without the need for any external software drivers. Mention that all PDA operating systems will recognize a wireless NIC.

Teaching

Tip / A common mistake when installing any hardware is not reading the manufacturer’s documentation.There are a wide variety of NICs produced by a number of manufacturers, and no two NICs are exactly the same.

Access Point

  1. Explain the purpose of the three main components of a wireless access point.

Teaching

Tip / It is possible to use a standard PC as an access point. Installing a wireless NIC (which functions as the transmitter/receiver), a standard NIC (which serves as the wired network interface), and special AP control software will allow a PC to serve as an AP.
  1. Discuss the two basic functions of a wireless access point. Illustrate with Figure 2-6.
  1. Describe the factors that affect the range of a wireless access point acting as a base station.
  1. Discuss the number of users that a wireless access point can support, and the factors that affect this number.
  1. Describe how Power over Ethernet can provide power to an AP without the need for a power outlet. Discuss the benefits of this capability, such as being able to place an AP in the best possible position.

Teaching

Tip / Power over Ethernet is now an IEEE standard known as 802.3af.

RemoteWirelessBridge

  1. Explain that a bridge is a device that is used to connect two network segments together, even if those segments use different types of physical media.
  1. Explain that a remote wireless bridge is a wireless device designed to connect two or more wired or wireless networks together. Discuss the differences between a remote wireless bridge and a WLAN AP.

Teaching

Tip / Most APs cannot be used in place of a remote wireless bridge. However, some enterprise-level APs, such as the Cisco Aironet 1200, can also perform as a remote wireless bridge.
  1. Discuss the characteristics of a remote wireless bridge. Illustrate a remote wireless bridge with Figure 2-7.
  1. Explain that remote wireless bridges have special software for transmitting and receiving signals. Discuss the concept of delay spread. Mention that remote wireless bridges also have software that allows them to select the clearest transmission channel and avoid noise and interference.
  1. Explain that remote wireless bridges have two types of connections. Illustrate the point-to-point and point-to-multipoint configurations using Figures 2-8 and 2-9 respectively.
  1. Discuss the four modes that a remote wireless bridge can be placed in. Illustrate root and non-root modes with Figure 2-10. Illustrate repeater mode with Figure 2-11.
  1. Discuss the basic transmission characteristics of remote wireless bridges, in terms of throughput and transmission distance.

Wireless Gateway

  1. Explain that a wireless gateway is a device that combines wireless management and security in a single appliance.
  1. Using the list on pages 42 and 43 of the text as a guide, discuss the functions performed by a wireless gateway.

Understanding Standards

  1. Provide an introduction to the concept of standards. Stress that standards make it easier for us to purchase and use a wide variety of products.
  1. Explain that wireless technology has relied on standards since its outset, and mention how this has assisted in the widespread acceptance of standards.

Teaching

Tip / As an example of how the lack of standards can affect consumer use of products, present the example of DVD+R versus DVD-R. Both are recordable DVD standards, but they were developed by different organizations, and are not necessarily compatible. Explain to the students that this incompatibility can mean that your DVDs recorded with one of these standards may not be able to be read by DVD players or disk drives that rely on the other standard.

The Need for Standards

  1. Explain that standards for telecommunications have been essential since the very beginning, and discuss why this is the case.
  1. Mention that some professionals in information technology believe that standards have stifled growth in the field, and explain the reasons why. Stress that, in reality, standards have proven more beneficial than harmful.

Advantages and Disadvantages of Standards

  1. Using the first list on page 45 of the text as a guide, discuss the advantages of standards. Define the term proprietary device. Stress that newer standards are generally backward compatible.

Teaching

Tip / Proprietary software is much more common that proprietary hardware devices and technologies.
  1. Using the second list on page 45 of the text as a guide, discuss the disadvantages of standards.

Teaching

Tip / An example of the ability for standards to be affect and be affected by political interests, have the students consider the Kyoto treaty. The United States has refused to embrace the Kyoto protocols, while almost every other industrialized nation has embraced them. This has generated political strife between the US and other nations.
  1. Summarize the advantages and disadvantages of standards using Table 2-1.

Types of Standards

  1. Provide a brief overview of the various types of standards.

De Facto

  1. Explain that de facto standards are not actually standards at all, but are common practices that the industry follows for various reasons, ranging from ease of use to tradition to what the majority of the users do.

Teaching

Tip / Explain that Microsoft Windows is the de facto standard operating system on the market today.

De Jure

  1. Explain that de jure standards are official standards, which are governed by an organization or body.
  1. Mention that the process of establishing de jure standards can be very involved. Give examples of how involved this process can be.

Teaching

Tip / The word de facto comes from Latin and means “from the fact.” The word de jure is also from Latin and means “from the law.”

Teaching

Tip / De facto standards sometimes become de jure standards by being later approved by a committee. Ethernet is one example of a de facto standard that later became a de jure standard.

Consortia

  1. Explain that one of the disadvantages of de jure standards is that they take a long time to complete.
  1. Define the term consortia. Explain that they are often used to create standards, and are usually industry-sponsored organizations that want to promote a specific technology.

Teaching

Tip / One of the most famous consortia is the World Wide Web Consortium (W3C), which is composed of industry giants such as Microsoft, Sun Microsystems, and IBM. The W3C is responsible for creating the standards that are widely used on the Internet today, including Hypertext Markup Language (HTML), Cascading Style Sheets (CSS), and the Document Object Model (DOM).

Enforcing Standards

  1. Discuss the importance of enforcing standards.
  1. Explain how the marketplace enforces some standards. Mention that standards created by consortia often are regulated by the marketplace.
  1. Explain that de jure standards must often be enforced by an outside regulatory agency. Stress that these regulatory agencies must have the power to enforce the standards and punish those who do not abide by them.

Teaching

Tip / An example of a regulatory agency that most students would be familiar with is the nuclear regulatory agency.

Quick Quiz 1

  1. The hardware that allows a client computer to be part of a wired network is called a(n) ______.

Answer: network interface card (NIC)

  1. True or False: One function of an AP is to act as a bridge between wireless and wired networks.

Answer: True

  1. A(n) ______is a wireless device designed to connect two or more wired or wireless networks together.

Answer: remote wireless bridge

  1. A(n) ______is a device that combines wireless management and security in a single appliance.

Answer: wireless gateway

  1. ______standards are official standards.

Answer: De jure

  1. ______are usually industry-sponsored organizations that want to promote a specific technology.

Answer: Consortia

Wireless Standards Organizations and Regulatory Agencies

  1. Provide a brief overview of the three primary standard-setting and regulatory bodies that play a major role in wireless LAN technology.

Institute of Electrical and Electronics Engineers (IEEE)

  1. Provide an overview of the history and mission of the IEEE. Explain that the IEEE is the world’s largest technical professional society, and discuss the activities that it is involved in. Specifically mention that it is actively involved in work on over 800 standards.
  1. Provide an introduction to the Project 802 standards. Mention that the specifications for Ethernet are defined by the Project 802.3 committee. Using Table 2-2 as a guide, discuss some of the Project 802 committees.

Wi-Fi Alliance

  1. Discuss the Wireless Ethernet Compatibility Alliance, mentioning its history and mission. Using the list on page 49 of the text as a guide, discuss the three main goals of the WECA.

Teaching

Tip / SOHO settings have been particularly eager to embrace wireless LAN technology. The sales of wireless LAN equipment to SOHO settings grew by 73% from 2003 to 2004, according to the Dell’Oro Group.
  1. Explain that WECA changed its name to the Wi-Fi Alliance. Explain that only products that have passed the Wi-Fi Alliance testing are allowed to refer to their products as Wi-Fi Certified. Illustrate the Wi-Fi Certified logo with Figure 2-12.
  1. Explain how the Wi-Fi Alliance is branching out by allowing businesses to apply to be registered as a Wi-Fi ZONE. Discuss the benefits of being registered as a Wi-Fi ZONE.

Federal Communications Commission (FCC)

  1. Provide a brief overview of the purpose of the FCC.

Responsibilities

  1. Explain that the FCC is the primary regulatory agency for wireless communications in the United States and its territorial possessions.
  1. Discuss the reason why the FCC was formed, and discuss its power structure. Explain that only three of the five commissioners may be members of the same political party, and none of them can have a financial interest in any FCC-related business.
  1. Stress that the FCC’s responsibilities are very broad. Discuss the various responsibilities shouldered by this agency.

Regulating the Radio Frequency Spectrum

  1. Provide an overview of the ways that the FCC plays a role in wireless communication standards and regulation. Stress that the FCC is charged with regulating the radio frequency spectrum.
  1. Discuss the radio frequency spectrum in detail. Explain how it is regulated by the FCC. Define the term band. Using Table 2-3 as a guide, discuss some of the more commonly used frequency bands.
  1. Explain the purpose of the license-exempt spectrum, stressing that the FCC created it to foster the development of a broad range of new devices and to stimulate the growth of new industries. Using Table 2-4 as a guide, discuss some of the FCC unregulated bands. Stress the ISM and U-NII bands, and explain how they are used by WLANS.
  1. Discuss the negative features of the unregulated bands.

Types of Wireless LANs

  1. Provide a brief overview of the wireless LAN standards that the IEEE has approved over the past few years.

IEEE 802.11

  1. Explain that the IEEE 802.11 standard specified that wireless transmissions could take place through infrared light or by sending radio signals.

Infrared Transmissions

  1. Define the term light spectrum. Explain where infrared light lies on the light spectrum.

Teaching

Tip / A useful tool here would be an illustration of the light spectrum. This should be easy to find on the internet. One site that contains such an illustration is:

Teaching

Tip / Infrared light is next to visible light on the light spectrum and shares many of the same characteristics.
  1. Discuss how infrared transmissions send data. Explain the roles of the emitter and detector in this process.

Teaching

Tip / Emitters and detectors are sometimes combined into a single device.
  1. Discuss how directed and diffused transmissions occur, using Figure 2-13 and 2-14, respectively, to illustrate.
  1. Discuss the advantages of infrared transmission. Stress the fact that infrared signals do not penetrate walls, and explain why this is beneficial.
  1. Using the list on page 55 of the text as a guide, discuss the disadvantages and limitations of infrared transmission.
  1. Explain that infrared transmission has never gained much popularity. Discuss a few of the devices that might use infrared transmission.

Teaching

Tip / WLANs that use infrared transmissions are used in specialized situations where radio signals would interfere with other equipment, such as in hospital operating rooms, or when security is a concern, such as in secure government buildings.

Radio Wave Transmissions

  1. Explain that radio wave can penetrate through solid objects, so radio wave transmission provides more mobility than infrared transmission.
  1. Compare the characteristics of radio waves to those of infrared. Explain that the IEEE 802.11 standard outlining the use of radio waves in transmissions has become the preferred method for wireless LANs.

Teaching

Tip / How radio waves actually carry data signals is covered in detail in Chapter 3.

IEEE 802.11b

  1. Explain that the bandwidth of 2 Mbps for the 802.11 standard introduced in 1997 was not sufficient for most network applications. Discuss the 802.11b amendment to the standard, mentioning that it added two higher speeds (5.5 Mbps and 11 Mbps) to the original 802.11 standard.
  1. Discuss the distance that 802.11b wireless devices can transmit over. Explain that when the devices fall out of range to transmit at 11 Mbps, the transmission speed is dropped to 5.5 Mbps.

IEEE 802.11a

  1. Explain that the IEEE 802.11a standard specifies a maximum rated speed of 54 Mbps and also supports 48, 36, 24, 18, 12, 9, and 6 Mbps transmissions using the U-NII band.
  1. Discuss why IEEE 802.11b is more prevalent than 802.11a, even though the standards were published at the same time.
  1. Explain that the distance limitations on 801.11a are more stringent than those for 802.11b.

IEEE 802.11g

  1. Discuss the (short) history of the 802.11g standard, explaining that it is intended to combine the best features of 802.11a and 802.11b. Mention that this standard was formally ratified in 2003.
  1. Discuss the role that major chip manufacturers had in the development of the 802.11g standard.
  1. Describe the transmission speed and distance characteristics of the 802.11g standard. Mention that the 802.11g standard specifies that devices operate entirely in the ISM frequency.

Teaching

Tip / Make sure that the students understand that the actual geographic range of any wireless technology depends on several factors, including the power of the antenna, physical barriers or obstacles between sending and receiving nodes, and interference in the environment. Therefore, although a technology is rated for a certain average geographic range, it may actually transmit signals in a shorter or longer range.

Projected IEEE 802.11n

  1. Provide an overview of the proposed IEEE 802.11n standard. Explain the committee is considering over 60 proposals for the standard, and mention that the transmission speed specified by this standard is expected to be between 100 and 500 Mbps.
  1. Explain that devices incorporating some of the 802.11n features may appear before the standard is officially ratified. Mention that this happened with 802.11g.

Teaching

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