Secure Wifi Essentials Flashcards
Introduction to Wifi Basics: Radio Frequencies
What are the key characteristics of the 2.4 GHz and 5/6 GHz frequency bands? [4]
Longer wavelengths mean that 2.4 GHz has a much better range than a 5 or 6 GHz wireless network.
Larger channel widths provide faster speed and throughput, but can create greater interference.
The 5 and 6 GHz bands support faster data rates at shorter distances than the 2.4 GHz band.
The 5 and 6 GHz bands are well suited for high density deployments because of the greater number channels that do not overlap, and the higher throughput available.
Introduction to Wifi Basics: Radio Frequencies
What is ‘Radio’? [2]
What does ‘Radio’ require? [3]
Radio is a transmission of modulated signals sent to a receiver.
Radio requires a transmitter, receiver, and the over-the-air medium between the transmitter and receiver.
Introduction to Wifi Basics: Frequency and Wavelength
The most basic component of radio communications is a radio wave. What is a radio wave? [2]
Describe some key points about radio waves. [6]
A radio wave is an electromagnetic wave of a specific frequency.
A wave cycle has a startpoint and an endpoint (wave length).
The frequency of a wave cycle is measured in Hertz. ( 1 Hz = 1 wave cycle a second).
The greater the frequency of the wave, the shorter the wavelength.
A radio frequency (RF) is a rate of oscillation.
An RF signal that oscillates 2.4 million times a second is 2.4 MHz (Megahertz).
Wifi signals in the 2.4, 5, and 6 GHz (Gigahertz) bands oscillate at 2.4, 5, and 6 billion times a second respectively.
Introduction to Wifi Basics: Wireless Bands and Channels
At what frequency range of the electromagnetic spectrum does the RF spectrum reside? [1]
What is done to avoid RF interference? [2]
What is a RF ‘band’? [2]
The 2.4 GHz, 5 GHz, and 6 GHz bands are used for wireless communication. What other devices/technologies use these bands? [4] [2]
3 Hz to 300 GHz
The use of the RF spectrum is heavily regulated and divided into radio usage bands.
A band is a section/range of the RF spectrum dedicated to a specific purpose.
2.4 GHz: Mobile devices, microwaves, wireless monitoring systems, and bluetooth devices.
5 GHz and 6 GHz: Radar and other radio-location systems.
Introduction to Wifi Basics: Wireless Channels
What is a wireless channel? [2]
What is a channel width? [2]
One key point about wireless channels. [1]
A wireless channel consists of a specific range of frequencies within an RF band.
A channel width is the range of frequencies within a wireless channel.
The frequency range of a channel overlaps adjacent channels and can create interference with other devices.
Introduction to Wifi Basics: Channel Width
What does channel width control? [3]
What channel widths does the 2.4 GHz band support? [2]
What channel widths does the 5 and 6 GHz bands support? [4]
One key point about channel widths. [1]
Channel width controls how broad the signal is and how many frequencies it uses. When the channel width increases, the speed and throughput of wireless transmissions also increases.
20 and 40 MHz channel widths.
20, 40, 80, and 160 MHz channel widths.
Greater channel widths provide faster speed and throughput, but can cause greater interference in high density areas, and decrease the number of available channels.
Introduction to Wifi Basics: Channel Width
What is WatchGuard’s recommendation in regards to channel widths? [4]
Start with 20 to 40 MHz channel widths.
Use higher channel widths only if you require very high application throughput demand in low density deployments with a small number of wireless devices.
Introduction to Wifi Basics: 2.4 GHz Band
How many dedicated channels are in the 2.4 GHz band? [2]
Describe the distribution of these channels across the 2.4 GHz band. [4]
There are 14 dedicated channels. Not all channels are available in every region.
Each channel is separated by 5 MHz, but because the channel width is 20 MHz, only three of these channels (1, 6, and 11) do not overlap.
To avoid interference, the above mentioned channels are most commonly used in 2.4 GHz wifi deployments.
Introduction to Wifi Basics: 2.4 GHz Band
The 2.4 GHz band has longer wavelengths than the 5 GHz band. Describe the benefits of this. [2]
Describe two disadvantages of the 2.4 GHz band. [2]
Describe a scenario where you would use the 2.4 GHz band. [2]
Longer wavelengths mean that 2.4 GHz has a much better range than 5 GHz. Also, 2.4 GHz radio waves can better penetrate solid obstructions.
The 2.4 GHz band is very congested because many other devices use this band.
THe 2.4 GHz band has few non-overlapping channels to help prevent co-channel interference.
Use the 2.4 GHz band when you require wider area coverage and support for legacy wireless devices.
Introduction to Wifi Basics: 5 and 6 GHz Bands
Describe 3 advantages of 5/6 GHz over 2.4 GHz, and anything that needs baring in mind. [3] [2]
What deployments are these bands well suited for? [2]
What is DFS? [4]
The 5 and 6 GHz bands have a greater bandwidth and a greater number of non-overlapping channels, depending on regional availability and channel width.
5/6 GHz supports faster data rates at shorter distances.
Well suited for high density deployments with many devices because of the greater number of non-overlapping channels.
Dynamic Frequency Selection allows wireless devices to share parts of the 5 and 6 GHz bands allocated to radar systems without interference to radar signals. When a wireless device detects radar on the channel it’s using, it immediately stops broadcasting on that channel, switches channel, and informs its clients to move to the new channel.
Channels reserved for radar/radio navigation depends on region.
Introduction to Wifi Basics: 2.4, 5, and 6 GHz Bands
What do you need to remember in regard to Max Data Rates? [3]
Max Data Rates are half-duplex and based on the theoretical maximum defined the the standard. Actual rates are much lower.
Introduction to Wifi Basics: Wireless Antennas
Describe the two types of antenna. [3] [4]
Omnidirectional Antenna:
Can transmit and receive with 360° coverage in all directions.
Most wifi access points and clients use these antennas to support connections from any direction and provide the widest signal coverage.
Directional Antenna:
Directs signals in the direction the antenna points to.
This provides a stronger signal because it’s focused in one direction; not spread out in 360°.
Typically used to extend wifi network range to difficult areas to reach, however you can also install them in situations where 360° coverage isn’t required.
