wireless standards Flashcards
Which of the following best describes the disabling of an SSID broadcast?
A ) It is one of the measures used in the process of securing wireless networks
B) It makes a WLAN harder to discover
C) It blocks access to a WAP
D) It prevents wireless clients from accessing the network
B) It makes a WLAN harder to discover
Wi-Fi Protected Setup (WPS) simplifies the configuration of new wireless networks by enabling non-technical users to easily set up new networks, configure network security settings and add new devices to an existing network. However, due to its known security vulnerabilities, WPS is not recommended and should be disabled.
True
False
True
Which of the following is the best method to secure a small network lacking an authentication server? WPA-PSK WPA2-Enterprise WPA2-PSK WPA-Enterprise
WPA2-PSK
What are the characteristic features of a WPA/WPA2 Enterprise mode? (Select 2 answers)
Suitable for large corporate networks
Does not require an authentication server
Suitable for all types of wireless LANs
Requires RADIUS authentication server
Suitable for large corporate networks
Requires RADIUS authentication server
Which of the following answers apply to the IEEE 802.11a wireless standard? (Select 2 answers)
2.4 GHz frequency band
Maximum data signaling rate of 54 Mbps
5.0 GHz frequency band
Maximum data signaling rate of up to 600 Mbps
5.4 GHz frequency band
Maximum data signaling rate of 11 Mbps
Maximum data signaling rate of 54 Mbps
5.0 GHz frequency band
802.11a (OFDM waveform)
Main article: IEEE 802.11a-1999
802.11a, published in 1999, uses the same data link layer protocol and frame format as the original standard, but an OFDM based air interface (physical layer) was added.
It operates in the 5 GHz band with a maximum net data rate of 54 Mbit/s, plus error correction code, which yields realistic net achievable throughput in the mid-20 Mbit/s.[35] It has seen widespread worldwide implementation, particularly within the corporate workspace.
Since the 2.4 GHz band is heavily used to the point of being crowded, using the relatively unused 5 GHz band gives 802.11a a significant advantage. However, this high carrier frequency also brings a disadvantage: the effective overall range of 802.11a is less than that of 802.11b/g. In theory, 802.11a signals are absorbed more readily by walls and other solid objects in their path due to their smaller wavelength, and, as a result, cannot penetrate as far as those of 802.11b. In practice, 802.11b typically has a higher range at low speeds (802.11b will reduce speed to 5.5 Mbit/s or even 1 Mbit/s at low signal strengths). 802.11a also suffers from interference,[36] but locally there may be fewer signals to interfere with, resulting in less interference and better throughput.
What are the characteristic features of the IEEE 802.11b wireless standard? (Select 2 answers)
Maximum data signaling rate of 11 Mbps
2.0 GHz frequency range
Maximum data signaling rate of 54 Mbps
5.0 GHz frequency range
Maximum data signaling rate of up to 600 Mbps
2.4 GHz frequency range
Maximum data signaling rate of 11 Mbps
2.4 GHz frequency range
802.11b
Main article: IEEE 802.11b-1999
The 802.11b standard has a maximum raw data rate of 11 Mbit/s (Megabits per second) and uses the same media access method defined in the original standard. 802.11b products appeared on the market in early 2000, since 802.11b is a direct extension of the modulation technique defined in the original standard. The dramatic increase in throughput of 802.11b (compared to the original standard) along with simultaneous substantial price reductions led to the rapid acceptance of 802.11b as the definitive wireless LAN technology.
Devices using 802.11b experience interference from other products operating in the 2.4 GHz band. Devices operating in the 2.4 GHz range include microwave ovens, Bluetooth devices, baby monitors, cordless telephones, and some amateur radio equipment. As unlicensed intentional radiators in this ISM band, they must not interfere with and must tolerate interference from primary or secondary allocations (users) of this band, such as amateur radio.
Which of the following answers apply to the IEEE 802.11g wireless standard? (Select 2 answers)
Maximum data signaling rate of up to 600 Mbps
5.4 GHz frequency band
Maximum data signaling rate of 54 Mbps
2.4 GHz frequency range
Maximum data signaling rate of 11 Mbps
5.0 GHz frequency range
Maximum data signaling rate of 54 Mbps
2.4 GHz frequency range
802.11g
Main article: IEEE 802.11g-2003
In June 2003, a third modulation standard was ratified: 802.11g. This works in the 2.4 GHz band (like 802.11b), but uses the same OFDM based transmission scheme as 802.11a. It operates at a maximum physical layer bit rate of 54 Mbit/s exclusive of forward error correction codes, or about 22 Mbit/s average throughput.[37] 802.11g hardware is fully backward compatible with 802.11b hardware, and therefore is encumbered with legacy issues that reduce throughput by ~21% when compared to 802.11a.[38]
The then-proposed 802.11g standard was rapidly adopted in the market starting in January 2003, well before ratification, due to the desire for higher data rates as well as reductions in manufacturing costs.[citation needed] By summer 2003, most dual-band 802.11a/b products became dual-band/tri-mode, supporting a and b/g in a single mobile adapter card or access point. Details of making b and g work well together occupied much of the lingering technical process; in an 802.11g network, however, the activity of an 802.11b participant will reduce the data rate of the overall 802.11g network.
Like 802.11b, 802.11g devices also suffer interference from other products operating in the 2.4 GHz band, for example, wireless keyboards.
The IEEE 802.11g standard is backwards compatible with:
- 11n
- 11a
- 11b
- 11ac
802.11b
802.11g
Main article: IEEE 802.11g-2003
In June 2003, a third modulation standard was ratified: 802.11g. This works in the 2.4 GHz band (like 802.11b), but uses the same OFDM based transmission scheme as 802.11a. It operates at a maximum physical layer bit rate of 54 Mbit/s exclusive of forward error correction codes, or about 22 Mbit/s average throughput.[37] 802.11g hardware is fully backward compatible with 802.11b hardware, and therefore is encumbered with legacy issues that reduce throughput by ~21% when compared to 802.11a.[38]
The then-proposed 802.11g standard was rapidly adopted in the market starting in January 2003, well before ratification, due to the desire for higher data rates as well as reductions in manufacturing costs.[citation needed] By summer 2003, most dual-band 802.11a/b products became dual-band/tri-mode, supporting a and b/g in a single mobile adapter card or access point. Details of making b and g work well together occupied much of the lingering technical process; in an 802.11g network, however, the activity of an 802.11b participant will reduce the data rate of the overall 802.11g network.
Like 802.11b, 802.11g devices also suffer interference from other products operating in the 2.4 GHz band, for example, wireless keyboards.
The IEEE 802.11n standard offers backward compatibility with: (Select all that apply)
- 11g
- 11ac
- 11b
- 11a
- 11g
- 11b
- 11a
802.11n
Main article: IEEE 802.11n-2009
802.11n is an amendment that improves upon the previous 802.11 standards; its first draft of certification was published in 2006. The 802.11n standard was retroactively labelled as Wi-Fi 4 by the Wi-Fi Alliance.[40][41] The standard added support for multiple-input multiple-output antennas (MIMO). 802.11n operates on both the 2.4 GHz and the 5 GHz bands. Support for 5 GHz bands is optional. Its net data rate ranges from 54 Mbit/s to 600 Mbit/s. The IEEE has approved the amendment, and it was published in October 2009.[42][43] Prior to the final ratification, enterprises were already migrating to 802.11n networks based on the Wi-Fi Alliance’s certification of products conforming to a 2007 draft of the 802.11n proposal.
Multiple Input / Multiple Output (MIMO) is a wireless technology that allows for significant increase in data throughput due to the use of multiple antennas and multiple data streams.
True
False
True
In radio, multiple-input and multiple-output, or MIMO (/ˈmaɪmoʊ, ˈmiːmoʊ/), is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation.[1] MIMO has become an essential element of wireless communication standards including IEEE 802.11n (Wi-Fi 4), IEEE 802.11ac (Wi-Fi 5), HSPA+ (3G), WiMAX, and Long Term Evolution (LTE). More recently, MIMO has been applied to power-line communication for three-wire installations as part of the ITU G.hn standard and of the HomePlug AV2 specification.[2][3]
At one time, in wireless the term “MIMO” referred to the use of multiple antennas at the transmitter and the receiver. In modern usage, “MIMO” specifically refers to a practical technique for sending and receiving more than one data signal simultaneously over the same radio channel by exploiting multipath propagation. Although the “multipath” phenomenon may be interesting, it is the use of orthogonal frequency-division multiplexing (OFDM) to encode the channels that is responsible for the increase in data capacity. MIMO is fundamentally different from smart antenna techniques developed to enhance the performance of a single data signal, such as beamforming and diversity.
Which of the following answers describe features of the IEEE 802.11ac wireless standard? (Select 3 answers)
Multiple Input / Multiple Output (MIMO)
Data signaling rate of up to 600 Mbps
5.0 GHz frequency band
Maximum data signaling rate of up to 6.77 Gbps
Multi-User Multiple Input / Multiple Output (MU-MIMO)
2.4 GHz frequency band
5.0 GHz frequency band
Maximum data signaling rate of up to 6.77 Gbps
Multi-User Multiple Input / Multiple Output (MU-MIMO)
802.11ac
Main article: IEEE 802.11ac
IEEE 802.11ac-2013 is an amendment to IEEE 802.11, published in December 2013, that builds on 802.11n.[46] The 802.11ac standard was retroactively labelled as Wi-Fi 5 by the Wi-Fi Alliance.[40][41] Changes compared to 802.11n include wider channels (80 or 160 MHz versus 40 MHz) in the 5 GHz band, more spatial streams (up to eight versus four), higher-order modulation (up to 256-QAM vs. 64-QAM), and the addition of Multi-user MIMO (MU-MIMO). The Wi-Fi Alliance separated the introduction of ac wireless products into two phases (“waves”), named “Wave 1” and “Wave 2”.[47][48] From mid-2013, the alliance started certifying Wave 1 802.11ac products shipped by manufacturers, based on the IEEE 802.11ac Draft 3.0 (the IEEE standard was not finalized until later that year).[49] In 2016 Wi-Fi Alliance introduced the Wave 2 certification, to provide higher bandwidth and capacity than Wave 1 products. Wave 2 products include additional features like MU-MIMO, 160 MHz channel width support, support for more 5 GHz channels, and four spatial streams (with four antennas; compared to three in Wave 1 and 802.11n, and eight in IEEE’s 802.11ax specification).[50][51]
Which of the following frequency bands can be used by IEEE 802.11 networks? (Select all that apply)
- 0 GHz
- 4 GHz
- 0 GHz
- 4 GHz
- 4 GHz
5. 0 GHz
What is the channel bandwidth specified in the IEEE 802.11a standard?
20 MHz
22 MHz
40 MHz
80 MHz
20 MHz
11a standard was released on September 1999. Networks using 802.11a operate at radio frequency of 5GHz and a bandwidth of 20MHz. The specification uses a modulation scheme known as orthogonal frequency-division multiplexing (OFDM) that is especially well suited to use in office settings.
Which of the following frequency bands can be used by IEEE 802.11a
- 0 GHz
- 4 GHz
- 0 GHz
- 4 GHz
- 0 GHz
- 11a is one of the original 802.11 wireless standards, from OCT 1999.
- 11a Operates in the 5GHz range
operates at 54 Mbit/s
smaller range than 802.11b
Which of the following is a channel bandwidth used in 802.11b networks? 20 MHz 22 MHz 40 MHz 80 MHz
22 MHz
The 22 MHz Wi-Fi channel bandwidth
