Wireless Networking (2.3) Flashcards
2.4GHz
Long range, slower speeds
14 designated channels, each 20MHz wide spaced 5MHz apart
Protocol requires 25MHz of channel separation which means that it is possible for adjacent channels to overlap and then interfere with each other. For this reason, only channels 1, 6, 11 are typically used in the US to avoid interference. In the rest of the world, the four channels 1, 5, 9, 13 are typically recommended. The 2.4-GHz frequency band is heavily used because most devices can operate on that band
5GHz
Short range, faster speeds
24 non-overlapping channels divided in four different sections: UNII-1, UNII-2, UNII-2 extended, UNII-3, and ISM. Each channel is 20MHz wide with 20MHz of space separating each channel
The 5-GHz band is actually four frequency bands: 5.1-GHz, 5.3-GHz, 5.4-GHz, and 5.8-GHz. The 5-GHz band has a total of 24 channels with 20 MHz bandwidth available. Unlike the 2.4-GHz band, the channels are non-overlapping, therefore all channels have the potential to be used in a single wireless system
Regulations
Most countries have regulations to manage Wi-Fi frequency use (spectrum, power output, interference requirements, etc.)
Bluetooth
PAN (Personal Area Network)
Uses 2.4GHz (same as 802.11)
ISM (Industrial, Scientific, and Medical) band
Short range (~10m for consumer devices, ~100m for industrial devices)
802.11a
OG 802.11 wireless standard (Oct 1999)
5GHz (or other frequencies with special licensing)
54Mbps
Short range (higher frequency absorbed by objects in the way)
Not common nowadays
802.11b
Another OG 802.11 standard (Oct 1999)
2.4GHz
11Mbps
Better range than 802.11a because it used a lower frequency (less absorption issues)
More frequency conflict (baby monitors, cordless phones, microwave ovens, Bluetooth)
Not common nowadays
802.11g
Upgrade from 802.11b (June 2003)
2.4GHz
54Mbps
Backwards compatible with 802.11b
Same frequency conflict problems as 802.11b
802.11n (Wi-FI 4)
Upgrade from 802.11g, 802.11b, and 802.11a (October 2009)
5GHz or 2.4GHz (40MHz channel widths)
600Mbps
Uses MIMO (Multiple-input, multiple-output)
Multiple transmit and receive antennas
802.11ac (Wi-Fi 5)
Significant improvements over 802.11n (January 2014)
5GHz (anything operating in 2.4GHz used 802.11n)
~7Gbps
Increased channel bonding (larger bandwidth usage)
Denser signaling modulation (faster data transfers)
8 MU-MIMO (Multi-User Multiple-Input Multiple Output) downlink streams…twice as many as 802.11n
802.11ax (Wi-Fi 6)
Wi-Fi 5’s successor (February 2021)
5GHz or 2.4GHz
20, 40, 60, and 160 MHz channel widths
1.2 Gbps per channel
8 bi-directional MU-MIMO streams
Uses OFDMA (Orthogonal Frequency Division Multiple Access)
Works similar to cellular communication
Improved high-density installations
Long-range fixed wireless
Connecting 802.11 between two buildings located miles from each other
Uses fixed directional antennas and increased signal strength
Focused point-to-point connection
Wireless regulations are complex (refer to country’s regulatory agency)
Unlicensed 2.4GHz/5GHz free to use (additional frequencies may be available but additional licensing may be required)
OUTDOOR ANTENNA INSTALLATION IS NOT TRIVIAL! GET AN EXPERT AND BE SAFE!
RFID
Radio-Frequency Identification
It’s everywhere (access badges, inventory/assembly live tracking, pet/animal chips, anything that needs to be tracked/traced)
Uses radar tech (radio energy transmitted to tag, RF powers tag, ID is transmitted back)
Can be scanned from front or back
Some RFID chips can be active/powered
NFC
Near Field Communication
Two-way wireless communication (built on RFID, though RFID is mostly one way)
Used for payment systems on your phone, bootstrapping for other wireless devices (NFC helps w/ Bluetooth paring), etc.
Short range w/ encryption support
