ch.four
wireless technology
Summary
■ Radio wave and microwave transmissions work on the principle of producing
a carrier wave as the means of communication between two network devices.
■ Modulation is the mixing of two radio signals, typically a carrier wave with a
data signal.
■ Infrared is used in line of sight transmissions and is not susceptible to radio
interference.
■ The FCC regulates the use of the electromagnetic spectrum by assigning
radio frequencies and maximum power ratings to devices.
■ A common source of interference for wireless networks is industrial,
scientific, and medical devices that use frequencies in the same range as
wireless networks.
■ Two main classifications of antennae based on the shape of the
electromagnetic wave pattern it produces are directional and omni.
■ Radio waves are electromagnetic waves that cover the 10 kHz to 3,000,000 MHz
frequency range.
■ Several transmission techniques are used to communicate between radio
wave-based network devices: single-frequency, spread-spectrum, and
orthogonal frequency-division multiplexing.
■ Spread spectrum is the radio transmission technique that subdivides the
allocated frequency range into smaller units called channels. The two types of
spread spectrum transmission techniques are frequency hopping and direct
sequencing.
■ Frequency hopping avoids interference by changing channels while
transmitting data.
■ Another name for frequency hopping is frequency hopping spread spectrum (FHSS).
■ Direct sequencing consists of 11 overlapping channels of 83 MHz each in
a 2.4-GHz spectrum. Within the 11 channels are three channels with a
22-MHz bandwidth. The three channels do not overlap and can be used
simultaneously.
■ Another name for direct sequencing is direct sequencing spread spectrum (DSSS).
■ Orthogonal frequency division multiplexing (OFDM) is similar to frequency
hopping and direct sequencing and employs multiplexing.
■ A Wireless Access Point (WAP) provides a connection between a wireless
network and a cable-based network. It also serves as the center of communication
in a wireless network.
■ A wireless network that contains one or more Wireless Access Points is
arranged in infrastructure mode.
■ A wireless network that does not contain a Wireless Access Point (WAP) is
arranged in ad hoc mode.
■ The IEEE 802.11a standard describes wireless networks operating at 5 GHz
with a maximum data rate of 54 Mbps.
■ The IEEE 802.11b standard describes wireless networks operating at 2.4 GHz
with a maximum data rate of 11 Mbps.
■ The IEEE 802.11g standard describes wireless networks operating at either
2.4 GHz or 5 GHz with a maximum data rate of 54 Mbps.
■ IEEE 802.11n standard operates at 5 GHZ and 2.4 GHz with a maximum data
rate of 300 Mbps to 600 Mbps.
■ Multiple Input Multiple Output (MIMO) uses two or more streams of data
transmission to increase data throughput and the range of the wireless
network. MIMO is described in the IEEE 802.11n standard.
■ Spatial multiplexing is the transmission of two or more streams of data
simultaneously.
■ IEEE 802.15 standard describes the use of Wireless Personal Area Networks
(WPANs).
■ Wireless networks specified under the IEEE 802.11 standard use Carrier
Sense Multiple Access with Collision Avoidance (CSMA/CA) as the media
access method.
■ Bluetooth is a standard developed by a group of manufacturers to allow their
devices to interoperate. Bluetooth is recognized by the 802.11 standard and is
used for short-range data transfer applications using the 2.4-GHz radio band.
■ Infrared is commonly used for point-to-point transmission between two
devices such as a personal digital assistant and a PC.
■ Satellite communications experience propagation delay because of the great
distance a signal must travel.
■ Wireless technology can be cost-effective when compared with cable-based
network media.
■ A disadvantage of employing wireless technology is security.
■ A Service Set Identifier (SSID) is similar in function to a workgroup name or
domain name and must be assigned to a Wireless Access Point (WAP).
■ Wireless networks are not secure when default settings are used for the
configuration.
■ Wireless encryption keys should be changed on a regular basis to maintain a
high degree of security.
■ Radio wave and microwave transmissions work on the principle of producing
a carrier wave as the means of communication between two network devices.
■ Modulation is the mixing of two radio signals, typically a carrier wave with a
data signal.
■ Infrared is used in line of sight transmissions and is not susceptible to radio
interference.
■ The FCC regulates the use of the electromagnetic spectrum by assigning
radio frequencies and maximum power ratings to devices.
■ A common source of interference for wireless networks is industrial,
scientific, and medical devices that use frequencies in the same range as
wireless networks.
■ Two main classifications of antennae based on the shape of the
electromagnetic wave pattern it produces are directional and omni.
■ Radio waves are electromagnetic waves that cover the 10 kHz to 3,000,000 MHz
frequency range.
■ Several transmission techniques are used to communicate between radio
wave-based network devices: single-frequency, spread-spectrum, and
orthogonal frequency-division multiplexing.
■ Spread spectrum is the radio transmission technique that subdivides the
allocated frequency range into smaller units called channels. The two types of
spread spectrum transmission techniques are frequency hopping and direct
sequencing.
■ Frequency hopping avoids interference by changing channels while
transmitting data.
■ Another name for frequency hopping is frequency hopping spread spectrum (FHSS).
■ Direct sequencing consists of 11 overlapping channels of 83 MHz each in
a 2.4-GHz spectrum. Within the 11 channels are three channels with a
22-MHz bandwidth. The three channels do not overlap and can be used
simultaneously.
■ Another name for direct sequencing is direct sequencing spread spectrum (DSSS).
■ Orthogonal frequency division multiplexing (OFDM) is similar to frequency
hopping and direct sequencing and employs multiplexing.
■ A Wireless Access Point (WAP) provides a connection between a wireless
network and a cable-based network. It also serves as the center of communication
in a wireless network.
■ A wireless network that contains one or more Wireless Access Points is
arranged in infrastructure mode.
■ A wireless network that does not contain a Wireless Access Point (WAP) is
arranged in ad hoc mode.
■ The IEEE 802.11a standard describes wireless networks operating at 5 GHz
with a maximum data rate of 54 Mbps.
■ The IEEE 802.11b standard describes wireless networks operating at 2.4 GHz
with a maximum data rate of 11 Mbps.
■ The IEEE 802.11g standard describes wireless networks operating at either
2.4 GHz or 5 GHz with a maximum data rate of 54 Mbps.
■ IEEE 802.11n standard operates at 5 GHZ and 2.4 GHz with a maximum data
rate of 300 Mbps to 600 Mbps.
■ Multiple Input Multiple Output (MIMO) uses two or more streams of data
transmission to increase data throughput and the range of the wireless
network. MIMO is described in the IEEE 802.11n standard.
■ Spatial multiplexing is the transmission of two or more streams of data
simultaneously.
■ IEEE 802.15 standard describes the use of Wireless Personal Area Networks
(WPANs).
■ Wireless networks specified under the IEEE 802.11 standard use Carrier
Sense Multiple Access with Collision Avoidance (CSMA/CA) as the media
access method.
■ Bluetooth is a standard developed by a group of manufacturers to allow their
devices to interoperate. Bluetooth is recognized by the 802.11 standard and is
used for short-range data transfer applications using the 2.4-GHz radio band.
■ Infrared is commonly used for point-to-point transmission between two
devices such as a personal digital assistant and a PC.
■ Satellite communications experience propagation delay because of the great
distance a signal must travel.
■ Wireless technology can be cost-effective when compared with cable-based
network media.
■ A disadvantage of employing wireless technology is security.
■ A Service Set Identifier (SSID) is similar in function to a workgroup name or
domain name and must be assigned to a Wireless Access Point (WAP).
■ Wireless networks are not secure when default settings are used for the
configuration.
■ Wireless encryption keys should be changed on a regular basis to maintain a
high degree of security.
Review Questions
Answer the following questions on a separate sheet of paper. Please do not write in this book.
1. A(n) _____ is an electromagnetic wave of a set frequency that is used to carry
data in radio wave- and microwave-based networks.
2. What is modulation?
3. A simple radio broadcast consists of a(n) _____, which generates a carrier
wave and a(n) _____, which receives a carrier wave.
4. What is a channel?
5. What are the two major classifications of antennae?
6. Which of the following antenna types is not used in point-to-point links?
A. Flat panel
B. Omni
C. Parabolic
D. Yagi
7. Which antenna style was developed with aesthetics in mind?
8. What is spread spectrum?
9. The spread spectrum technique that transmits data on multiple channels
simultaneously is called _____.
10. The spread spectrum technique that transmits data on multiple channels
sequentially is called _____.
11. Why is frequency hopping used?
12. The _____ transmission technique uses the 5-GHz frequency and can achieve
data rates as high as 54 Mbps.
13. List the frequency range and related power rating of each of the three U-NII
classifications.
14. What is an SSID?
15. What frequency does the IEEE 802.11a standard specify, and what is the
maximum achievable distance?
16. What frequency does IEEE 802.11b standard specify, and what is the
maximum achievable distance?
17. What frequencies does IEEE 802.11g standard specify, and what are the
related maximum achievable distances?
18. What is the maximum throughput based on the IEEE 802.11n standard?
19. Which media access method does the 802.11 wireless standard specify?
20. What is the difference between CSMA/CA and CSMA/CD?
21. What does the acronym MIMO represent?
22. What is MIMO wireless technology?
23. What is the maximum achievable distance of a Bluetooth device?
24. What is the data rate of the Bluetooth 2.0 standard?
25. What is the data rate of the Bluetooth 3.0 standard?
26. Which IEEE specification addresses WPAN?
27. _____ technology is based on radio waves connecting to designated areas
referred to as cells.
28. What is a disadvantage of satellite communications?
29. What is a geosynchronous orbit?
30. What is generally the maximum amount of satellite transmission delay
acceptable for telephone conversations?
31. What is an advantage of wireless networking?
32. What is the one major disadvantage of wireless technology?
33. What does the acronym WEP represent?
34. Write an example of an encryption key.
35. What does the acronym CCKM represent?
Answer the following questions on a separate sheet of paper. Please do not write in this book.
1. A(n) _____ is an electromagnetic wave of a set frequency that is used to carry
data in radio wave- and microwave-based networks.
2. What is modulation?
3. A simple radio broadcast consists of a(n) _____, which generates a carrier
wave and a(n) _____, which receives a carrier wave.
4. What is a channel?
5. What are the two major classifications of antennae?
6. Which of the following antenna types is not used in point-to-point links?
A. Flat panel
B. Omni
C. Parabolic
D. Yagi
7. Which antenna style was developed with aesthetics in mind?
8. What is spread spectrum?
9. The spread spectrum technique that transmits data on multiple channels
simultaneously is called _____.
10. The spread spectrum technique that transmits data on multiple channels
sequentially is called _____.
11. Why is frequency hopping used?
12. The _____ transmission technique uses the 5-GHz frequency and can achieve
data rates as high as 54 Mbps.
13. List the frequency range and related power rating of each of the three U-NII
classifications.
14. What is an SSID?
15. What frequency does the IEEE 802.11a standard specify, and what is the
maximum achievable distance?
16. What frequency does IEEE 802.11b standard specify, and what is the
maximum achievable distance?
17. What frequencies does IEEE 802.11g standard specify, and what are the
related maximum achievable distances?
18. What is the maximum throughput based on the IEEE 802.11n standard?
19. Which media access method does the 802.11 wireless standard specify?
20. What is the difference between CSMA/CA and CSMA/CD?
21. What does the acronym MIMO represent?
22. What is MIMO wireless technology?
23. What is the maximum achievable distance of a Bluetooth device?
24. What is the data rate of the Bluetooth 2.0 standard?
25. What is the data rate of the Bluetooth 3.0 standard?
26. Which IEEE specification addresses WPAN?
27. _____ technology is based on radio waves connecting to designated areas
referred to as cells.
28. What is a disadvantage of satellite communications?
29. What is a geosynchronous orbit?
30. What is generally the maximum amount of satellite transmission delay
acceptable for telephone conversations?
31. What is an advantage of wireless networking?
32. What is the one major disadvantage of wireless technology?
33. What does the acronym WEP represent?
34. Write an example of an encryption key.
35. What does the acronym CCKM represent?