Network+ and Wireless Standards

If you're preparing for the Network+ exam, you probably know that a good portion includes wireless topics including wireless standards. If you can master some basic facts on wireless standards, you'll be able to ace many Network+ questions without any trouble at all.  Another post covered Network+ and Wireless Encryption topics.

Several objectives address wireless standards directly:

• 2.2 Given a scenario, install and configure a wireless network. (This objective includes "Frequencies", "Wireless standards", and "Compatibility (802.11 a/b/g/n)"
• 2.4 Given a scenario, troubleshoot common wireless problems. (This objective includes "Configurations", and "Incompatibilities")
• 3.3 Compare and contrast different wireless standards. (This objective includes "802.11 a/b/g/n standards")

Network+ Practice Test Questions

Here are a couple of practice test questions you can use to check your knowledge of the Network+ wireless standards.

Q1. You are tasked with configuring a wireless network that can support legacy devices and operate on both 2.4 GHz and 5 GHZ. What would you use?

A. 802.11a
B. 802.11b
C. 802.11g
D. 802.11n

Q2. Which of the following wireless standards operates at 5 GHz and has a maximum speed of 54 Mbps?

A. 802.11a
B. 802.11b
C. 802.11g
D. 802.11n

Q3. Which of the following wireless standards supports multiple transceivers within a single WAP?

A. 802.11a
B. 802.11b
C. 802.11g
D. 802.11n

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802.11a

The 802.11a standard is one of the early wireless standards and it was released in 1999. It uses Orthogonal frequency-division multiplexing (OFDM) in the 5 GHz frequency range. One of the reasons 5 GHz was selected is to avoid the interference in the noisier 2.4 GHz frequency range. The original specification had 12 non-overlapping channels that could be used compared with the three non-overlapping channels supported in 802.11b and 802.11g. It also uses dynamic frequency selection (DFS) allowing the device to automatically switch channels when it detected interference. Radar technologies use portions of the 5 GHz range so DFS is useful to avoid interference from radar sources.

Unfortunately, 802.11a signals are much more susceptible to interference from physical objects such as walls and have the lowest transmission distance of the four standards. The maximum range of 802.11a is often quoted as 30 meters (about 98 feet) but this can be affected by the signal strength of the wireless access point (WAP) and interference sources.

It’s rare to see new 802.11a wireless devices today. However, you might run across some legacy devices using 802.11a.

802.11b

The 802.11b standard came out at about the same time as 802.11a. It operates in the 2.4 GHz frequency range, has a maximum speed of 11 Mbps, and a mildly longer range than 802.11a. Compared with 802.11a, 802.11g, and 802.11n, it is the only standard that uses Direct-sequence spread spectrum (DSSS). 802.11b uses 22 MHz wide channels with some regions allowing as many as 13 channels. Commonly used non-overlapping channels are 1, 6, and 11. While 802.11b was more popular than 802.11a, it is rarely used today.

802.11g

The 802.11g standard was released in 2003 and up until the release of 802.11n has been the most popular. It supports speeds up to 54 Mbps, operates in the 2.4 GHz range and has a slightly longer range than 802.11b. It uses 20 MHz wide channels and channels 1, 6, and 11 are commonly used as non-overlapping channels. As with 802.11a and 802.11n, 802.11g uses OFDM.

One significant difference with 802.11g over 802.11a and 802.11b is that it supports channel bonding. This was also known as Super G and wasn’t supported by all wireless devices. When supported, Super G increased the maximum throughput from 54 Mbps to 108 Mbps.

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802.11n and MIMO

The newest standard is 802.11n and it is proving to be far superior to the three previous 802.11 standards. It is the fastest and supports speeds up to 600 Mbps and can operate in both the 2.4 GHz and 5 GHz frequency spectrums. It also has the longest range with distances up to 70 meters. As with 802.11a and 802.11g, it uses OFDM.

A significant difference with 802.11n is the use of a smart antenna technology called multiple input multiple output (MIMO) to achieve faster speeds. MIMO includes multiple antennas and transceivers to simultaneously transmit and receive data over multiple streams. MIMO can include as many as four streams of communication with each stream supporting up to 150 Mbps. When four streams are used, it supports connections up to 600 Mbps.

The multiple antennas used with MIMO provide diversity gain which improves the overall link reliability. These streams are sent separately in a process called spatial multiplexing.

Another difference with 802.11n is that it supports 20 MHz channels just like 802.11g and it also supports 40 MHz channels for greater throughput. When 40 MHz channels are used it is often referred to as channel bonding.

Many wireless networks have a combination of both 802.11g and 802.11n devices. An 802.11n WAP can support both standards. Also, they can be configured to use only 2.4 GHz or a combination of 2.4 GHz and 5 GHz.

If you create a network using all 802.11n devices and they all support 5 GHz, you can configure the WAP to use only 5 GHz. Because this frequency band has less interference you can often get much better throughput. However, before switching over, it’s important to verify that all the devices support 5 GHz because it isn’t required. Many vendors create 802.11n wireless devices using only 2.4 GHz to make the devices more affordable.

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Answer to Practice Test Question 1

Q1. You are tasked with configuring a wireless network that can support legacy devices and operate on both 2.4 GHz and 5 GHZ. What would you use?
A. 802.11a
B. 802.11b
C. 802.11g
D. 802.11n

Answer 1. D is correct. Only an 802.11n network will operate on both 2.4 GHz and 5 GHz frequencies. 802.11n networks can also support older (legacy) devices because it is backwards compatible with earlier wireless standards.

802.11a only uses 5 GHZ.

802.11b and 802.11g only uses 2.4 GHz.

Answer to Practice Test Question 2

Q2. Which of the following wireless standards operates at 5 GHz and has a maximum speed of 54 Mbps?
A. 802.11a
B. 802.11b
C. 802.11g
D. 802.11n

Answer 2. A is correct. The 802.11a standard operates at 5 GHz and has a maximum speed of 54 Mbps.

802.11b and 802.11g both operate at 2.4 GHz.

802.11n uses 2.4 GHz and 5 GHz but it has a maximum transfer rate of 600 Mbps, not 54 Mbps.

Answer to Practice Test Question 3

Q3. Which of the following wireless standards supports multiple transceivers within a single WAP?
A. 802.11a
B. 802.11b
C. 802.11g
D. 802.11n

Answer 3. D is correct. 802.11n uses multiple input multiple output (MIMO) technologies and MIMO supports multiple transceivers within a single wireless access point (WAP).

MIMO is not supported in 802.11a, 802.11b, or 802.11g.

Summary

Here's a short summary of some of the key characteristics with each of the different wireless standards.

802.11a

• Maximum speed of 54 Mbps
• Operates in the 5 GHz frequency range
• Shortest distance - can travel about 35 meters (about 115 feet)

802.11b

• Maximum speed of 11 Mbps
• Operates in the 2.4 GHz frequency range
• Can travel about 35 meters (about 115 feet)

802.11g

• Maximum speed of 54 Mbps
• Operates in the 2.4 GHz frequency range
• Can travel about 38 meters (about 125 feet)
• Supports channel bonding with Super G (combines two 54 Mbps channels to give 108 Mbps max speed)

802.11n

• Maximum speed of 600 Mbps
• Operates in the 2.4 GHz and 5 GHz frequency ranges
• Longest distance - can travel about 70 meters (about 230 feet)
• Uses MIMO supporting multiple transceivers within a single wireless access point
• Can use 40 MHz channels (referred to as channel bonding