Network+ Guide to Networks, 6th Edition
Chapter 8
Wireless Networking
At a Glance
Instructor’s Manual Table of Contents

Overview

Objectives

Teaching Tips

Quick Quizzes

Class Discussion Topics

Additional Projects

Additional Resources

Key Terms
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Lecture Notes
Overview
The Earth’s atmosphere provides an intangible means of transporting data over networks. For
decades, radio and TV stations have used the atmosphere to transport information via analog
signals. Such analog signals are also capable of carrying data. Networks that transmit signals
through the atmosphere via radio frequency (RF) waves are known as wireless networks or
WLANs (wireless local area networks). Wireless transmission media is now common in business
and home networks and necessary in some specialized network environments. In this chapter, the
student will learn how data travels through the air and how to make it happen on their network.
Chapter Objectives
After reading this chapter and completing the exercises, the student will be able to:
 Explain how nodes exchange wireless signals
 Identify potential obstacles to successful wireless transmission and their repercussions,
such as interference and reflection
 Understand WLAN (wireless LAN) architecture
 Specify the characteristics of popular WLAN transmission methods, including 802.11
a/b/g/n
 Install and configure wireless access points and their clients
 Describe wireless WAN technologies, including 802.16 (WiMAX), HSPA+, LTE and
satellite communications
Teaching Tips
The Wireless Spectrum
1. Define the term wireless spectrum.
2. Explain how wireless spectrum waves are arranged.
3. Use Figure 8-1 to illustrate the wireless spectrum and the major wireless services
associated with each frequency range.
4. Describe the role of the FCC with respect to managing the wireless spectrum in the
United States.
5. Describe the role of the ITU with respect to managing the wireless spectrum
internationally.
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The FCC Wireless Telecommunications Bureau (WTB) handles nearly all FCC
Teaching
domestic wireless telecommunications programs, policies, and outreach initiatives.
Tip
Go to http://wireless.fcc.gov and review the services and materials available.
Characteristics of Wireless Transmission
1. Describe the characteristics wireless transmissions have in common with wired
transmissions.
2. Describe the differences between wireless and wired transmissions.
3. Explain how wireless signals travel from the transmitter to the receiver.
a. Emphasize the role of the antenna.
4. Use Figure 8-2 to illustrate wireless transmission and reception.
Antennas
1. Introduce the concept of an antenna noting that each type of wireless service requires an
antenna specifically designed for that service.
2. Define the term radiation pattern.
3. Define the term directional antenna and provide examples of its use.
4. Define the term omnidirectional antenna and provide examples of its use.
5. Define and explain the term range.
Signal Propagation
1. Introduce the concept of signal propagation noting that ideally, a wireless signal would
travel directly in a straight line from its transmitter to its intended receiver.
2. Define and explain LOS (line-of-sight) propagation.
3. Explain the options available when an obstacle stands in a signal’s way.
a. The signal may pass through the object.
b. The signal may be absorbed by the object.
c. The signal may be subject to any of the following phenomena: reflection,
diffraction, or scattering.
4. Note that the object’s geometry governs which of these three phenomena occurs.
5. Define and explain the term reflection.
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6. Define and explain the term diffraction.
7. Define and explain the term scattering.
8. Define multipath signals noting the advantage and disadvantage they present.
9. Use Figure 8-3 to illustrate multipath signals caused by reflection, diffraction, and
scattering.
Signal Degradation
1. Define and explain fading.
2. Define and explain attenuation.
3. Describe the impact of noise on wireless signals.
4. Explain why interference is a significant problem for wireless communications.
Frequency Ranges
1. Describe the 2.4-GHz band.
2. Define the term unlicensed.
3. Describe the 5-GHz band.
Narrowband, Broadband, and Spread Spectrum Signals
1. Introduce narrowband, broadband, and spread spectrum signals noting that they define
wireless spectrum use.
2. Define and explain narrowband.
3. Define an explain broadband.
4. Define and explain spread-spectrum.
5. Define and describe FHSS (frequency hopping spread spectrum).
6. Define and describe DSSS (direct-sequence spread spectrum).
Fixed versus Mobile
1. Describe fixed communication wireless systems.
2. Describe mobile communication wireless systems.
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Quick Quiz 1
1. True or False: All wireless signals are carried through the air by electromagnetic waves.
Answer: True
2. The ____________________ is a continuum of the electromagnetic waves used for data
and voice communication.
Answer: wireless spectrum
3. ____________________ are used for both the transmission and reception of wireless
signals.
Answer: Antennas
4. ____ signals follow a number of different paths to their destination because of reflection,
diffraction, and scattering.
a. Multipath
b. Opened
c. Closed
d. Variable
Answer: A
5. Wireless signals cannot depend on a(n) ____________________ or shielding to protect
them from extraneous EMI.
Answer: conduit
6. True or False: Spread-spectrum signaling is a popular way of making wireless
transmissions more secure.
Answer: True
WLAN (Wireless LAN) Architecture
1. Explain why wireless networks are not laid out using the same topologies as wired
networks.
2. Describe an ad hoc WLAN.
3. Define an access point and provide alternative names for it.
4. Use Figure 8-6 to illustrate an ad hoc WLAN.
5. Describe an infrastructure WLAN.
6. Use Figure 8-7 to illustrate an infrastructure WLAN.
7. Note that it is common for a WLAN to include several access points.
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8. Explain why mobile networking allows roaming wireless nodes.
9. Explain why wireless technology can be used to connect two different parts of a LAN or
two separate LANs.
10. Use Figure 8-8 to illustrate wireless LAN interconnection.
11. Explain the advantage of having WLANs support the same protocols (for example,
TCP/IP) and operating systems (for example, UNIX, Linux, or Windows) as wired
LANs.
802.11 WLANs
1. Introduce 802.11 WANs, noting that the evolution of wireless access methods did not
follow one direct and cooperative path, but grew from the efforts of multiple vendors and
organizations.
2. Introduce wireless technology standards.
3. Introduce Wi-Fi (wireless fidelity) standards.
Access Method
1. Introduce and describe 802.11 MAC services frame modifications.
2. Note the significance of using the same physical addressing scheme as Ethernet.
3. Describe three characteristics of wireless devices that distinguish them from wired
devices.
a. Emphasize the difference in access method.
4. Explain the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) access
method.
a. Note the significance of using ACK packets to verify every transmission.
5. Describe the RTS/CTS (Request to Send/Clear to Send) protocol.
Association
1. Introduce the concept of association by noting that association involves a number of
packet exchanges between an access point and a computer.
a. Note that association is another function of the MAC sublayer described in the
802.11 standard.
2. Define the term scanning.
3. Describe active scanning and passive scanning.
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4. Define an SSID and explain its significance.
5. Define the BSS (basic service set) and explain its significance.
6. Define the ESS (extended service set) and explain its significance.
7. Use Figure 8-10 to illustrate a network with a single BSS.
8. Use Figure 8-11 to illustrate a network encompassing multiple BSSs that form an ESS.
9. Emphasize what happens if a station detects the presence of several access points.
a. Explain why this process can present a security risk for any station within range
of a powerful, rogue access point.
10. Explain why a network with several authorized access points in an ESS requires a station
to be able to associate with any access point while maintaining network connectivity.
11. Define and explain reassociation.
12. Note that on a network with multiple access points, network managers can take advantage
of the stations’ scanning feature to automatically balance transmission loads between
those access points.
Teaching Explain why it is best to use access points manufactured by the same company
when designing an 802.11 network.
Tip
Frames
1. Review the types of overhead required to manage access to the 802.11 wireless networks.
2. Note that for each function, the 802.11 standard specifies a frame type at the MAC
sublayer:
a. ACKs, probes, beacons
3. Introduce and describe the three groups for these multiple frame types:
a. Control, management, data
4. Compare a basic 802.11 data frame with an Ethernet_II (DIX) frame (Figure 8-12).
5. Describe the significant fields in an 802.11 data frame contributing to data frame
overhead.
6. Point out that although 802.11b, 802.11a, 802.11g, and 802.11n share all of the MAC
sublayer characteristics described in the previous sections, they differ in their modulation
methods, frequency usage, and ranges.
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802.11b
1. Describe the 802.11b standard.
802.11a
1. Describe the 802.11a standard.
802.11g
1. Describe the 802.11g standard.
802.11n
1. Describe the 802.11n standard.
2. Note how the 802.11n standard differs from 802.b.
3. Note how the 802.11n standard differs from 802.11a and 802.11g.
4. Describe 802.11n innovations:
a. MIMO (multiple input-multiple output)
b. Channel bonding
c. Higher modulation rates
d. Frame aggregation
5. Use Figure 8-13 to illustrate an 802.11n access point with three antennas.
6. Use Figure 8-15 to illustrate the relatively low overhead of an aggregated 802.11n frame.
7. Note that 802.11n is backward compatible with previous Wi-Fi standards; however in
mixed environments, some of the new standard’s techniques for improving throughput
will not be possible.
Teaching Provide a live demonstration by navigating to the Wi-Fi Alliance homepage at
http://www.wi-fi.org and reviewing the material available at the site.
Tip
8. Use Table 8-1 to compare the common wireless networking standards, their ranges, and
throughputs.
Implementing a WLAN
1. Introduce the topics covered in this section:
a. Designing a small WLAN
b. Formation of larger, enterprise-wide WANs
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c. Installing and configuring access points and clients
d. Implementation pitfalls
Determining the Design
1. Describe how an access point might function if there is only one in the network.
a. Note considerations involved with access point WLAN placement.
2. Use Figure 8-16 to illustrate a home or small office WLAN arrangement.
3. Explain why in larger WLAN environments, a systematic approach to access point
placement is necessary.
4. Define and describe a site survey.
5. Point out the enterprise-wide WLAN design consideration.
6. Use Figure 8-17 to illustrate an enterprise-wide WLAN.
Configuring Wireless Connectivity Devices
1. Review the steps to configure an access point.
Configuring Wireless Clients
1. Review the steps to configure a Windows 7 client using a graphical interface.
2. Note that the iwconfig command may be used in UNIX and Linux environments to
view and set wireless interface parameters.
3. Use Figure 8-18 to illustrate output from the iwconfig command.
Avoiding Pitfalls
1. Describe the items that may cause issues in wireless configuration and explain how to
avoid or correct them.
Wireless WANs
1. Introduce and describe wireless broadband.
2. Review how access points figure into home networks and enterprise wide LANs.
a. Note that most networks use the 802.11b or 802.11g access methods.
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3. Define and describe a hotspot.
b. Explain that a hotspot may accept a user’s connection based on his or her MAC
address.
Provide an example of a commercial hotspot by visiting the T-mobile hot spot Web
Teaching
site at https://selfcare.hotspot.t-mobile.com/locations/viewLocationMap.do and
Tip
reviewing the material available there.
Cellular
1. Define and describe cellular networks.
2. Explain the architecture of cellular networks using Figure 8-22.
3. Describe the performance characteristics of the digital cellular networks.
4. Use Table 8-2 to describe the characteristics of some of the latest wireless WAN services.
802.16 (WiMAX)
5. Define and describe WiMAX.
6. Describe the two distinct advantages WiMAX has over Wi-Fi.
7. Discuss possible best uses for WiMAX.
8. Review residential installation of WiMAX.
9. Use Figure 8-21 to illustrate WiMAX residential service installation.
10. Use Figure 8-20 to illustrate a WiMAX residential antenna.
11. Describe WiMAX MAN service.
12. Note the one big disadvantage of WiMAX at this time.
Provide a live demonstration by navigating to the Discovery Channel site at
Teaching
http://dsc.discovery.com/technology/tech-10/wireless-cities-top.html to illustrate 10
Tip
cities with widespread wireless Internet.
Satellite Internet Access
1. Introduce satellite Internet access by explaining where it is best utilized.
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2. Define and describe geosynchronous orbit.
3. Define and describe LEO (low Earth orbiting) satellites.
4. Use Figure 8-23 to illustrate satellite communication.
5. Define and describe MEO (medium Earth orbiting) satellites.
6. Note that geosynchronous orbiting satellites are the most popular for satellite Internet
access.
7. Describe satellite frequencies.
8. Note the bands that satellite Internet access providers use.
9. Describe satellite Internet services.
a. Explain the dial return arrangement service.
b. Explain the satellite return arrangement service.
Teaching Provide a live demonstration by navigating to the Clearwire Web site at
http://www.clearwire.com to illustrate their Internet access offerings.
Tip
Quick Quiz 2
1. ____________________ networking allows wireless nodes to roam from one location to
another within a certain range of their access point.
2. Answer: Mobile
3. The four 802.11 standards (802.11b, 802.11a, 802.11g, 802.11n) are collectively known
as ____.
a. WiMAX
b. Wi-Fi
c. Bluetooth
d. Open
Answer: B
4. True or False: 802.11 networks use the same access method as Ethernet networks.
Answer: False
5. The 802.11 standard specifies a frame type at the ____________________ sublayer.
Answer: MAC
6. ____ orbiting satellites are the type used by the most popular satellite Internet access
service providers.
Answer: Geosynchronous
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Class Discussion Topics
1. Take a student poll of Wi-Fi use (802.11b, 802.11a, 802.11g, and 802.11n). Which
standard is used the most by the class? Have the class discuss their experiences with the
technology they use. Ask students to explain why they have or have not moved to the
newer 802.11n standard.
2. WiMAX showed great promise for convenient and fast connectivity; however,
deployment has stalled and there is a great deal of competition from cellular technologies,
especially LTE. Discuss the technology in terms of its potential positive and negative
impacts to society.
Additional Projects
1. Have students research the AT&T network of hot spots across the nation. Each student
should write a report summarizing his or her findings.
2. Have students research satellite Internet access. Students may select a vendor supplying
the service, a manufacturer, or a technology. Each student should write a report
summarizing his or her findings.
Additional Resources
1. The ABCs of securing your wireless network
http://arstechnica.com/security/news/2008/04/wireless-security.ars
2. Wi-Fi Certified Products
http://www.wi-fi.org/wi-fi-certified%E2%84%A2-products
3. IEEE Commentary: WiMax and Wi-Fi: Separate and Unequal
http://www.spectrum.ieee.org/mar04/3977
4. 10 Cities With Widespread Wireless Internet
http://dsc.discovery.com/technology/tech-10/wireless-cities-top.html
5. How WiFi Works
http://computer.howstuffworks.com/wireless-network.htm
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Key Terms
 1G The first generation of mobile phone services, popular in the 1970s and 1980s, which
were entirely analog.
 2.4-GHz band The range of radio frequencies from 2.4 to 2.4835 GHz. The 2.4-GHz
band, which allows for 11 unlicensed channels, is used by WLANs that follow the
popular 802.11b and 802.11g standards. However, it is also used for cordless telephone
and other transmissions, making the 2.4-GHz band more susceptible to interference than
the 5-GHz band.
 2G Second-generation mobile phone service, popular in the 1990s. 2G was the first
standard to use digital transmission, and as such, it paved the way for texting and media
downloads on mobile devices.
 3G Third-generation mobile phone service, released in the early 2000s, that specifies
throughputs of 384 Kbps and packet switching for data (but not voice) communications.
 4G Fourth-generation mobile phone service that is characterized by an all-IP, packetswitched network for both data and voice transmission. 4G standards, released in 2008,
also specify throughputs of 100 Mbps for fast-moving mobile clients, such as those in
cars, and 1 Gbps for slow-moving mobile clients, such as pedestrians.
 5-GHz band A range of frequencies that comprises four frequency bands: 5.1 GHz, 5.3
GHz, 5.4 GHz, and 5.8 GHz. It consists of 24 unlicensed bands, each 20-MHz wide. The
5-GHz band is used by WLANs that follow the 802.11a and 802.11n standards.
 802.11a The IEEE standard for a wireless networking technique that uses multiple
frequency bands in the 5-GHz frequency range and provides a theoretical maximum
throughput of 54 Mbps. 802.11a’s high throughput, compared with 802.11b, is
attributable to its use of higher frequencies, its unique method of encoding data, and more
available bandwidth.
 802.11b The IEEE standard for a wireless networking technique that uses DSSS (directsequence spread spectrum) signaling in the 2.4–2.4835-GHz frequency range (also called
the 2.4-GHz band). 802.11b separates the 2.4-GHz band into 14 overlapping 22-MHz
channels and provides a theoretical maximum of 11-Mbps throughput.
 802.11g The IEEE standard for a wireless networking technique designed to be
compatible with 802.11b while using different encoding techniques that allow it to reach
a theoretical maximum capacity of 54 Mbps. 802.11g, like 802.11b, uses the 2.4-GHz
frequency band.
 802.11n The IEEE standard for a wireless networking technique that may issue signals in
the 2.4- or 5-GHz band and can achieve actual data throughput between 65 and 600
Mbps. It accomplishes this through several means, including MIMO, channel bonding,
and frame aggregation. 802.11n is backward compatible with 802.11a, b, and g.
 802.16 An IEEE standard for wireless MANs. 802.16 networks may use frequencies
between 2 and 66 GHz. Their antennas may operate in a line-of-sight or non-line-of-sight
manner and cover 50 kilometers (or approximately 30 miles). 802.16 connections can
achieve a maximum throughput of 70 Mbps, though actual throughput diminishes as the
distance between transceivers increases. Several 802.16 standards exist. Collectively,
they are known as WiMAX.
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 802.16e Currently, the most widely implemented version of WiMAX. With 802.16e,
IEEE improved the mobility and QoS characteristics of the technology, making it better
suited to VoIP and mobile phone users. 802.16e is capable of 70-Mbps throughput, but
because bandwidth is shared and service providers cap data rates, most users actually
experience 1–4Mbps throughput.
 802.16m Also known as WiMAX 2, the IEEE standard for a version of 802.16 that
achieves theoretical throughputs of 330 Mbps with lower latency and better quality for
VoIP applications than previous WiMAX versions. 802.16m has been approved as a true
4G technology. Manufacturers expect it to reach throughputs of 1 Gbps in the near future.
access point A device used on wireless LANs that transmits and receives wireless signals
to and from multiple nodes and retransmits them to the rest of the network segment.
Access points can connect a group of nodes with a network or two networks with each
other. They may use directional or omnidirectional antennas.
 active scanning A method used by wireless stations to detect the presence of an access
point. In active scanning, the station issues a probe to each channel in its frequency range
and waits for the access point to respond.
 ad hoc A type of wireless LAN in which stations communicate directly with each other
(rather than using an access point).
 AP See access point.
 association In the context of wireless networking, the communication that occurs
between a station and an access point to enable the station to connect to the network via
that access point.
 backhaul An intermediate connection between subscriber networks and a
telecommunications carrier’s network.
 base station See access point.
 basic service set See BSS.
 basic service set identifier See BSSID.
 beacon frame In the context of wireless networking, a frame issued by an access point to
alert other nodes of its existence.
 bounce See reflection.
 BSS (basic service set) In IEEE terminology, a group of stations that share an access
point.
 BSSID (basic service set identifier) In IEEE terminology, the identifier for a BSS (basic
service set).
 Carrier Sense Multiple Access with Collision Avoidance See CSMA/CA.
 cell In a cellular network, an area of coverage serviced by an antenna and base station.
 channel bonding In the context of 802.11n wireless technology, the combination of two
20-MHz frequency bands to create one 40-MHz frequency band that can carry more than
twice the amount of data that a single 20-MHz band could. It’s recommended for use
only in the 5-GHz range because this band has more available channels and suffers less
interference than the 2.4-GHz band.
 CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) A network
access method used on 802.11 wireless networks. In CSMA/CA, before a node begins to
send data it checks the medium. If it detects no transmission activity, it waits a brief,
random amount of time, and then sends its transmission. If the node does detect activity,
it waits a brief period of time before checking the channel again. CSMA/CA does not
eliminate, but minimizes, the potential for collisions.
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 diffraction In the context of wireless signal propagation, the phenomenon that occurs
when an electromagnetic wave encounters an obstruction and splits into secondary
waves. The secondary waves continue to propagate in the direction in which they were
split. If you could see wireless signals being diffracted, they would appear to be bending
around the obstacle. Objects with sharp edges—including the corners of walls and
desks—cause diffraction.
 direct-sequence spread spectrum See DSSS.
 directional antenna A type of antenna that issues wireless signals along a single
direction, or path.
 downlink In the context of wireless transmission, the connection between a carrier’s
antenna and a client’s transceiver—for example, a smartphone.
 DSSS (direct-sequence spread spectrum) A transmission technique in which a signal’s
bits are distributed over an entire frequency band at once. Each bit is coded so that the
receiver can reassemble the original signal upon receiving the bits.
 ESS (extended service set) A group of access points and associated stations (or basic
service sets) connected to the same LAN.
 ESSID (extended service set identifier) A special identifier shared by BSSs that belong
to the same ESS.
 extended service set See ESS.
 extended service set identifier See ESSID.
 fading A variation in a wireless signal’s strength as a result of some of the
electromagnetic energy being scattered, reflected, or diffracted after being issued by the
transmitter.
 FHSS (frequency hopping spread spectrum) A wireless signaling technique in which a
signal jumps between several different frequencies within a band in a synchronization
pattern known to the channel’s receiver and transmitter.
 fixed A type of wireless system in which the locations of the transmitter and receiver are
static. In a fixed connection, the transmitting antenna focuses its energy directly toward
the receiving antenna. This results in a point-to-point link.
 frequency hopping spread spectrum See FHSS.
 GEO (geosynchronous earth orbit) The term used to refer to a satellite that maintains a
constant distance from a point on the equator at every point in its orbit. Geosynchronous
orbit satellites are the type used to provide satellite Internet access.
 geosynchronous earth orbit See GEO.
 handoff The transition that occurs when a cellular network client moves from one
antenna’s coverage area to another.
 High Speed Packet Access Plus See HSPA+.
 HSPA+ (High Speed Packet Access Plus) A 3G mobile wireless technology released in
2008 that uses MIMO and sophisticated encoding techniques to achieve a maximum 84Mbps downlink throughput and 11-Mbps uplink throughput in its current release.
Advances in more efficiently using limited channels and incorporating more antennas in
MIMO promise to push the maximum downlink data rate to 336 Mbps.
 infrastructure WLAN A type of WLAN in which stations communicate with an access
point and not directly with each other.
 iwconfig A command-line utility for viewing and setting wireless interface parameters on
Linux and UNIX workstations.
 line-of-sight See LOS.
 Long Term Evolution See LTE.
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 LOS (line-of-sight) A wireless signal or path that travels directly in a straight line from
its transmitter to its intended receiver. This type of propagation uses the least amount of
energy and results in the reception of the clearest possible signal.
 LTE (Long Term Evolution) A 4G cellular network technology that achieves downlink
data rates of up to 1 Gbps and uplink rates up to 500 Mbps. AT&T and Verizon have
adopted LTE for their high-speed wireless data networks.
 MIMO (multiple input-multiple output) In the context of 802.11n wireless networking,
the ability for access points to issue multiple signals to stations, thereby multiplying the
signal’s strength and increasing their range and data-carrying capacity. Because the
signals follow multipath propagation, they must be phase-adjusted when they reach their
destination.
 mobile A type of wireless system in which the receiver can be located anywhere within
the transmitter’s range. This allows the receiver to roam from one place to another while
continuing to pick up its signal.
 mobile switching center See MSC.
 mobile telecommunications switching office See MSC.
 MSC (mobile switching center) A carrier’s facility to which multiple cellular base
stations connect. An MSC might be located inside a telephone company’s central office
or it might stand alone and connect to the central office via fiber-optic cabling or a
microwave link. Equipment at an MSC manages mobile clients, monitoring their location
and usage patterns, and switches cellular calls. It also assigns each mobile client an IP
address.
 MTSO (mobile telecommunications switching office) See MSC.
 multipath The characteristic of wireless signals that follow a number of different paths
to their destination (for example, because of reflection, diffraction, and scattering).
 multiple input-multiple output See MIMO.
 narrowband A type of wireless transmission in which signals travel over a single
frequency or within a specified frequency range.
 omnidirectional antenna A type of antenna that issues and receives wireless signals
with equal strength and clarity in all directions. This type of antenna is used when many
different receivers must be able to pick up the signal, or when the receiver’s location is
highly mobile.
 passive scanning In the context of wireless networking, the process in which a station
listens to several channels within a frequency range for a beacon issued by an access
point.
 probe In 802.11 wireless networking, a type of frame issued by a station during active
scanning to find nearby access points.
 radiation pattern The relative strength over a three-dimensional area of all the
electromagnetic energy an antenna sends or receives.
 range The geographical area in which signals issued from an antenna or wireless system
can be consistently and accurately received.
 reassociation In the context of wireless networking, the process of a station establishing
a connection (or associating) with a different access point.
 reflection In the context of wireless, the phenomenon that occurs when an
electromagnetic wave encounters an obstacle and bounces back toward its source. A
wireless signal will bounce off objects whose dimensions are large compared with the
signal’s average wavelength.
 Request to Send/Clear to Send See RTS/CTS.
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 roaming In wireless networking, the process that describes a station moving between
BSSs without losing connectivity.
 RTS/CTS (Request to Send/Clear to Send) An exchange in which a wireless station
requests the exclusive right to communicate with an access point and the access point
confirms that it has granted that request.
 scanning The process a wireless station undergoes to find an access point. See also active
scanning and passive scanning.
 scattering The diffusion of a wireless signal that results from hitting an object that has
smaller dimensions compared with the signal’s wavelength. Scattering is also related to
the roughness of the surface a wireless signal encounters. The rougher the surface, the
more likely a signal is to scatter when it hits that surface.
 service set identifier See SSID.
 site survey In the context of wireless networking, an assessment of client requirements,
facility characteristics, and coverage areas to determine an access point arrangement that
will ensure reliable wireless connectivity within a given area.
 spread spectrum A type of wireless transmission in which lower-level signals are
distributed over several frequencies simultaneously. Spread-spectrum transmission is
more secure than narrowband.
 SSID (service set identifier) A unique character string used to identify an access point
on an 802.11 network.
 station An end node on a network; used most often in the context of wireless networks.
 transponder The equipment on a satellite that receives an uplinked signal from Earth,
amplifies the signal, modifies its frequency, then retransmits it (in a downlink) to an
antenna on Earth.
 uplink In the context of wireless transmission, the connection between a client’s
transceiver and a carrier’s antenna.
 WAP (wireless access point) See access point.
 Wi-Fi See 802.11.
 WiMAX See 802.16.
 WiMAX 2 See 802.16m.
 wireless A type of signal made of electromagnetic energy that travels through the air.
 wireless access point See access point.
 wireless gateway An access point that provides routing functions and is used as a
gateway.
 wireless LAN See WLAN.
 wireless router An access point that provides routing functions.
 wireless spectrum A continuum of electromagnetic waves used for data and voice
communication. The wireless spectrum (as defined by the FCC, which controls its use)
spans frequencies between 9 KHz and 300 GHz. Each type of wireless service can be
associated with one area of the wireless spectrum.
 WLAN (wireless LAN) A LAN that uses wireless connections for some or all of its
transmissions.
 Worldwide Interoperability for Microwave Access (WiMAX) See 802.16a.