Class notes · Professor Messer, CompTIA A+ 220-1201 Core 1 · Objective 2.2

Quick reference: the short version of this lesson is the Wireless Networking Protocols cheat sheet, part of Section 2.

Learning objectives

By the end of these notes you should be able to:

Explain who standardises Wi-Fi, and match 802.11 standard names to their Wi-Fi generation names.
Describe the three Wi-Fi frequency bands and how channels relate to frequencies.
Explain bandwidth in the 802.11 sense, and compare channel availability across the three bands.
Describe Bluetooth, its frequency band, and its typical range.
Explain the unlicensed ISM band and why it matters.
Describe RFID, including passive and active tags, and common uses.
Explain NFC, how it builds on RFID, and its common uses.

1. Who standardises Wi-Fi

When people say “wireless networking”, they usually mean the network used at home or work to reach other devices and the internet. This is standardised by the IEEE — the Institute of Electrical and Electronics Engineers — specifically by its 802.11 Committee. That’s why these are called 802.11 networks.

1.1 802.11 names vs Wi-Fi generation names

The 802.11 Committee felt that names like “802.11ac” were confusing for everyday use, so newer standards also get a simpler Wi-Fi generation name:

802.11 standard

Wi-Fi name

802.11ac

Wi-Fi 5

802.11ax

Wi-Fi 6, and Wi-Fi 6E (Extended)

802.11be

Wi-Fi 7

Instead of remembering the 802.11 letter codes, you can just say “Wi-Fi 6” or “Wi-Fi 7”.

2. Frequencies and channels

2.1 The three bands

Wi-Fi can use several frequency ranges, and different standards support different bands. Most Wi-Fi networks and devices use:

Band

Notes

2.4 GHz

The oldest, most crowded band

5 GHz

More spectrum, more channels

6 GHz

The newest, with the most spectrum

Some access points and devices can use more than one band simultaneously.

2.2 Channels instead of frequencies

Rather than remembering exact frequency values, the 802.11 Committee groups frequencies into channels — a simpler way to refer to a particular slice of spectrum. Your device’s Wi-Fi settings show the channel it’s using, not the raw frequency.

Worked example — reading channel numbers. On one device:

2.4 GHz, channel 6 → this corresponds to 2.437 GHz in the IEEE standard.
5 GHz, channel 44 → this corresponds to 5.220 GHz.

It’s far easier to say “channel 44” than “5.220 GHz” — that’s the whole point of channel numbers.

2.3 Bandwidth

Bandwidth, in this context, is how much spectrum a single Wi-Fi connection uses. Common values are:

20 MHz
40 MHz
80 MHz
160 MHz

A wider bandwidth uses more spectrum for one connection, generally allowing more throughput.

2.4 Comparing the three bands

Band

Available channels/spectrum

Bandwidth options

Interference

2.4 GHz

Limited — only three non-overlapping 20 MHz channels

Mainly 20 MHz

High, especially in crowded areas

5 GHz

Much more spectrum

20, 40, 80 or 160 MHz

Lower

6 GHz

The most spectrum of all

20, 40, 80 or 160 MHz, with the most room to use them

Lowest

Why 5 GHz and 6 GHz exist: 2.4 GHz has relatively little usable spectrum. In a confined space with many wireless networks nearby, that crowding causes interference. Moving to 5 GHz — and now 6 GHz — gives far more frequencies (and wider bandwidth options) to work with, reducing that congestion.

Note (beyond this lesson): the three non-overlapping 2.4 GHz channels referred to here are channels 1, 6 and 11 — the same set covered in the Section 2 networking notes.

3. Bluetooth

Bluetooth is a different wireless technology, commonly used for wireless headsets and wireless speakers connecting to a computer or phone.

Feature

Detail

Frequency

2.4 GHz

Band type

Part of the unlicensed ISM frequencies

Range (consumer devices)

About 10 metres maximum

3.1 ISM band

ISM stands for Industrial, Scientific and Medical. These are unlicensed frequencies — no special licence is required to use them. That’s precisely why you can simply turn on a laptop or phone and connect to Wi-Fi or Bluetooth without applying for any kind of spectrum licence.

3.2 Range: 802.11 vs Bluetooth

802.11 (Wi-Fi)

Bluetooth

Typical range

Enough to move around a building

About 10 metres (consumer devices)

Typical use

The network for a whole site

Personal devices connected to you

Because of its shorter range, Bluetooth suits devices that travel with you — headsets, speakers, wearables — rather than a whole building’s network.

4. RFID

RFID (Radio Frequency Identification) is used in many everyday situations:

Use

Example

Access control

Building access badges

Retail and manufacturing

Tags inside products, or tracked along an assembly line

Animal identification

A chip inside a pet, scanned to identify the owner

4.1 Tag types

Type

Power source

Range

Passive

No battery. Sits with no power until a scanner’s radio signal powers it

Short — you need to bring the scanner close

Active

Has its own battery

Longer — can be scanned from further away

Physical forms:

A tiny tag, roughly the size of a grain of rice — implanted in pets, for example.
A flat tag, as found in an access card — a printed antenna around the outside, with the RFID chip in the middle.

4.2 How a passive tag works

The tag sits completely unpowered.
A scanner is brought close.
The radio frequency energy from the scanner is enough to power the tag.
The scanner reads an ID code from the tag.
That code is compared against a database to determine what — or who — the tag represents.

4.3 Worked example — choosing a tag type

Scenario

Tag type

Why

An employee access badge, tapped at the door

Passive

No battery to maintain; short range is fine, even desirable

A pet microchip

Passive

Small, maintenance-free, lasts the animal’s lifetime

Tracking a shipping container across a large yard

Active

Needs to be read from much further away than a passive tag allows

5. NFC

NFC (Near Field Communication) builds on RFID technology, but extends it further.

RFID

NFC

Direction

Generally one-way (scanner reads the tag)

Two-way communication

Typical devices

Tags, badges, chips

Phones, smartwatches

5.1 Common uses

Use

Example

Payment

Tapping a phone or smartwatch at a point-of-sale terminal

Device setup

A phone using NFC to pass Bluetooth or Wi-Fi configuration parameters to a new device, so it can join the network

Identification / access

Using a phone (instead of a badge) to open a door

5.2 Worked example — pairing a speaker with NFC

A new Bluetooth speaker supports NFC pairing.

The user taps their phone against the NFC symbol on the speaker.
NFC’s two-way link passes the Bluetooth connection details to the speaker automatically.
The devices pair without manually searching the Bluetooth device list and entering a code.
Once paired, actual audio still travels over Bluetooth — NFC only helped with the setup step.

6. Security perspective

2.4 GHz interference isn’t just annoying — it can mask problems. A congested band can look like a connectivity fault when it’s really contention for limited channels. Moving affected devices to 5 GHz or 6 GHz, or changing channel, often resolves it.
The ISM band being unlicensed cuts both ways. Anyone can transmit on it — including attackers running rogue access points or jamming equipment. Always verify you’re joining the legitimate network (correct SSID and authentication), not a lookalike.
RFID and NFC don’t inherently encrypt. A basic passive RFID badge can potentially be cloned by someone with the right reader held close enough. More secure systems use encrypted or rolling-code tags.
Bluetooth’s short range is a partial defence, not a complete one. Directional antennas can extend an attacker’s effective range well beyond the “typical” 10 metres. Turn Bluetooth off when not in use, and don’t accept unexpected pairing requests.
NFC’s very short range (centimetres) makes casual eavesdropping harder, but keep payment authentication (PIN, biometric) enabled as a second layer.

Summary

Wi-Fi is standardised by the IEEE 802.11 Committee. Modern standards also carry simpler names: 802.11ac = Wi-Fi 5, 802.11ax = Wi-Fi 6 / 6E, 802.11be = Wi-Fi 7.
Three frequency bands: 2.4 GHz (limited, only three non-overlapping 20 MHz channels), 5 GHz and 6 GHz (much more spectrum and wider bandwidth options — up to 160 MHz).
Channels are a simpler way to refer to specific frequencies (e.g. channel 6 = 2.437 GHz; channel 44 = 5.220 GHz).
Bandwidth is how much spectrum one connection uses: 20, 40, 80 or 160 MHz.
Bluetooth uses 2.4 GHz, part of the unlicensed ISM band, with a consumer range of about 10 metres — suited to personal devices like headsets and speakers.
RFID tags can be passive (no battery, powered by the scanner, short range) or active (battery-powered, longer range). Used for access badges, retail/manufacturing tracking and pet identification.
NFC builds on RFID with two-way communication, used for payments, device pairing/configuration, and phone-based access.

Glossary

Term

Definition

IEEE

Institute of Electrical and Electronics Engineers

802.11

The IEEE committee and standard family for Wi-Fi

Wi-Fi 5 / 6 / 6E / 7

Simplified names for 802.11ac / ax / ax (extended) / be

Frequency band

A range of radio frequencies, e.g. 2.4 GHz, 5 GHz, 6 GHz

Channel

A named slice of spectrum within a band, simpler than quoting a frequency

Bandwidth (wireless)

The amount of spectrum used by one connection

Interference

Disruption from other devices or networks sharing the same spectrum

Bluetooth

A short-range wireless technology for personal devices

ISM band

Industrial, Scientific and Medical — unlicensed radio frequencies

Unlicensed spectrum

Frequencies usable without a specific licence

RFID

Radio Frequency Identification

Passive tag

An RFID tag with no battery, powered by the scanner’s signal

Active tag

An RFID tag with its own battery, readable from further away

NFC

Near Field Communication — short-range, two-way wireless

Point-of-sale (POS) terminal

The payment device at a shop checkout

Review questions

Which organisation, and which committee, standardises Wi-Fi?
Match the Wi-Fi generation names to their 802.11 standards: Wi-Fi 5, Wi-Fi 6, Wi-Fi 7.
What is a channel, and why is it more convenient than quoting a raw frequency?
What frequency does 2.4 GHz channel 6 correspond to?
Why does the 2.4 GHz band suffer more interference than 5 GHz or 6 GHz?
List four common Wi-Fi bandwidth values.
What frequency band does Bluetooth use, and what’s its typical consumer range?
What does ISM stand for, and why does it matter that these frequencies are unlicensed?
What’s the difference between a passive and an active RFID tag?
Describe, step by step, how a passive RFID badge is read.
Name two everyday uses of RFID besides access badges.
How does NFC differ from RFID?
Give two common uses of NFC.
A phone uses NFC to help a new speaker join a Bluetooth connection. Once paired, which technology actually carries the audio?

Answer key

The IEEE (Institute of Electrical and Electronics Engineers), via its 802.11 Committee.
Wi-Fi 5 = 802.11ac. Wi-Fi 6 (and 6E) = 802.11ax. Wi-Fi 7 = 802.11be.
A channel is a simpler label for a specific slice of spectrum, easier to remember and communicate than an exact frequency value.
2.437 GHz.
2.4 GHz has relatively little usable spectrum — only three non-overlapping 20 MHz channels — so networks nearby easily interfere with each other. 5 GHz and 6 GHz offer far more spectrum.
20, 40, 80 and 160 MHz.
2.4 GHz; about 10 metres for consumer devices.
Industrial, Scientific and Medical. Being unlicensed means no special permission is needed to transmit on them, which is why Wi-Fi and Bluetooth just work out of the box.
A passive tag has no battery and is powered by the scanner’s signal, giving it a short range. An active tag has its own battery and can be read from further away.
The tag sits unpowered; a scanner is brought close; the scanner’s radio energy powers the tag; the scanner reads the tag’s ID code; that code is compared against a database.
Any two of: tags inside retail products, tracking along an assembly line, identifying pets via an implanted chip.
NFC supports two-way communication, while RFID is generally one-way (a reader scanning a tag).
Any two of: point-of-sale payments; passing Bluetooth/Wi-Fi setup details to a new device; phone-based door access or identification.
Bluetooth. NFC only helps set up the connection; the audio itself travels over Bluetooth.