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In this section, we will dissect CompTIA 220-901 sub objective 2.5 which deals with wireless encryption standards and encryption. The 802.11 family is an important area to understand and fundamentally is specification based, consisting of alpha designations, frequencies, speeds, distances, and common problems. These are all testable. We’ll also follow that up with covered encryption types.
We will try to keep it simple while conveying the pertinent information about the 802.11 a/b/g/n/ac family. This is your key to defining the standard and its capabilities and compatibilities. Understand that different countries have different regulations regarding radio power levels (range) and the number of channels available for transmission. We will deal exclusively with the US specification.
In the US, we have 11 channels available of the 14 possible in the 2.4GHz frequency, of which only non-overlapping channels can be used. Channel 14 is unavailable because it does not have the required channel separation. Each transmission channel takes 20 – 22MHz and must be separated by roughly 16 to 22MHz, leaving only three free channels for practical use. These free channels are 1, 6 and 11 for 802.11b/g/n. In a pure 802.11n zone, 40MHz a channel is used. This is easily understood in the graphic shown.
2.4 GHz channels
You can see if you used channel 4 with 802.11b/g/n, your transmissions be corrupted by both channels 1 and 6. As a technician, this is one of the settings you would check to resolve a Wi-Fi connection or quality problem. Backward compatibility is also something to check. If you are using 802.11n in compatibility mode and your users are not getting the advertised speeds, you can attribute this issue to the bandwidth reduction adjustments needed to comply with the earlier standards. The only way to get the full value of the “n” channel is to operate in 802.11n only mode and to upgrade the older NICs. This is best conveyed in the following graphic if you consider that the 40MHz “n” channel is broken down to comply with the “b/g” modes when they are used.
Non overlapping channels
When we reference frequencies, the 2.4GHz frequency band is everything between 2.4 and 2.5 GHz. The 5GHz frequency band is roughly everything between 5.1 and 5.8GHz.
Now down to the specs.
This standard is capable of 54Mbps transmissions of up to 50 meters in the 5GHz band. This is essentially a deprecated standard.
This is the first widely adopted Wi-Fi standard. This offers 11Mbps speed with a distance of 100 meters, with direct line of sight (outdoors), in the more crowded 2.4 GHz band. It is susceptible to interference from household devices such as cordless phones and microwave ovens.
This standard is capable of 54 Mbps speed with a distance of up to 100 meters outdoors in the 2.4GHz band.
This standard is capable of speeds up to 600Mbps using up to four emulated full-duplex Multi In Multi Out (MIMO) antennae. These antennae can send and receive virtually simultaneously, using Time Division Multiplexing (TDM) which slices the transmissions into imperceptible chunks that give the impression of full-duplex. All 802.11 family standards are half-duplex. Before this advancement, Wi-Fi signals did not use the multiplexing duplex and as a result, only one party in the communication could send data at a time. TDM, along with multiple antennae, greatly increased performance. 802.11n operates in both the 2.4 and 5 GHz bands for backward compatibility. As with any radio-based transmissions, the signal weakens as the distance from the transmitter increases.
This is the latest implemented standard and can theoretically reach speeds of up to 7 Gbps using up to eight antennae. The additional antennae allow the 802.11ac standard to utilize a theoretical channel bandwidth of 80 to 160 MHz.
80 80 MHz and 160 MHz are new with 802.11ac
802.11 ac covers the same distance as 802.11n. The maximum distance is 70 meters indoors and 250 meters outdoors in the 5GHz band, making it backwards compatible to 802.11n only. Interestingly, the signal strength does not weaken at the outer perimeters of coverage. It’s all or nothing. By default Wi-Fi signals are omni-directional as are the signals from a radio station, distributing the signal evenly across the coverage area. 802.11ac standardizes the use of beamforming technology which focuses the transmissions directionally to active devices, strengthening the signal directionally as opposed to the shotgun blast nature of traditional Wi-Fi. This gives each device a longer, stronger, and faster signal that is less likely to encounter significant interference.
Beamforming technology
Currently, the recipient of the transmission must support beamforming for it to be effective.
Here’s a short table that summarizes most of the testable material discussed above.
Wireless standards for A+ 220-1001 Sub-Objective 2.4
Initial Bluetooth wireless connections were not as fast as its contemporaries (initially 2MBs). Since that time, the ranges and speeds have been increasing fairly steadily as shown in the table. Special protocol features allow users to create Personal Area Networks (PAN).
Characteristics of different Bluetooth versions
Let’s start with the Connection types available for mobile devices and their accessories. We have already discussed Wi-Fi and Bluetooth in detail (in prior ExamNotes) but there is a third type that you need to learn about. This is Near Field Communication (NFC). NFC is not a new technology and has experienced resurgence through the proliferation of mobile devices due to its main security feature, its 10 cm transmission range. Attackers have to be almost touching to be able to exchange data.
NFC can be used for tap and pay, which exchanges payment information with a NFC capable reader at the cash register, as well as exchanging contact information with friends or clients simply by tapping compatible phones together. The ultimate business card!
For authentication/security purposes, Radio Frequency Identification (RFID) can be used to transmit a security token wirelessly without any additional user input. An RFID tag can also be used to track inventory and many other objects including your pets!
In a nutshell, Zigbee is a PAN or wireless ad-hoc network. It is simpler than Wi-Fi or Bluetooth. Zigbee is a low power, short range solution that uses low bandwidth transmitting in the 5 GHz or 900 MHz bands with 20 meter indoor range. It is ideal for home automation and medical applications because it creates a mesh network. Zigbee is incompatible with Z-Wave.
Z-Wave is a competing home automation technology. Z-Wave uses the 900 MHz band. It shares the low power and low data rate properties of Zigbee but has a bit more range.
3G is the third generation of mobile wireless technology. Compared with 2G, its main benefits are higher speed (20 Mbps), better A/V capabilities, and global roaming. Along with its voice and data capabilities, Internet browsing was made possible on cellular devices.
4G offers even faster connections, taking the buffering and jitter out of streaming media.
LTE stands for Long Term Evolution as it pertains to mobile data. While switching from 3G to 4G is a noticeable improvement, adding LTE to 4G provides data rates that are roughly ten times that of 3G.
5G is where the fun starts! While not available at the time of this writing, 5G should be spreading by the time you take the test. 5G speeds will optimally be in the 500MBps range. This increase may cause users to abandon their wired broadband connection in favor of 5G. Home routers offering this speed will be available. Before you ditch your cable, consider that 5G service will be costly.
That’s all for 220-1001 Sub-objective 2.4. Good luck on the test!
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