Configuring Wireless Networks

Question 1

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

Answer 1

Carrier sense: Device checks if the channel is clear.
Collision Avoidance: Device waits before transmitting. If a frame is received intact then receiver replies with ACK. Otherwise, the sender resends until a timeout.

Question 2

Multiple Input Multiple Output (MIMO)

Answer 2

Uses multiple antennas to transmit and receive simultaneously. Increases bandwidth through spatial multiplexing (sending different streams over different antennas). For a single user. Transmation can be done one at a time

Question 3

Spatial Multiplexing

Answer 3

Provides more bandwidth for example creates different streams to different antennas

Question 4

Spatial Diversity

Answer 4

Stronger signal and better range (example, same stream from multiple antennas)

Question 5

Frequency Bands

Answer 5

• 2.4 GHz: Congested, limited to ~3 non-overlapping channels
• 5 GHz: Cleaner, more room (~25 non-overlapping channels)

Question 6

Channel Bonding

Answer 6

Combines two 20 MHz channels into one 40 MHz channel.
It is easier to do in 5 GHz due to more space.

Question 7

Orthogonal Frequency-Division Multiple Access (OFDMA)

Answer 7

a technology that allows multiple users to share the same frequency band simultaneously by dividing it into smaller, orthogonal subcarriers.

Question 8

Wi-Fi 5 (802.11ac)

Answer 8

• Very high throughput
• Only uses 5 GHz frequency band.
• Channel bonding: Up to 80 MHz or 160 MHz channels.
• Up to 8 streams

Question 9

Wi-Fi 6 (802.11ax)

Answer 9

• High Efficiency
• Uses 2.4, 5, and 6 GHz
• speed designed to approach 10 Gbps
• OFDMA
• Allows service class prioritization
• IoT friendly
• Backward compatible meaning works with older versions

Question 10

Multiuser MIMO

Answer 10

Multiple users can send streams of data to multiple devices simultaneously.

Question 11

Band Steering

Answer 11

Encourages devices to use less crowded frequency bands like 5 GHz or 6 GHz. Devices use signal strength and beacon messages to choose a frequency band. Many devices choose 2.4 by default but if 2.4 frequency band is hidden or delayed then devices connect to 5 or 6 GHz.

Question 12

Downlink MU-MIMO

Answer 12

• AP and clients must support MU-MIMO.
• Wi-Fi 5: Up to 4 clients over 5 GHz
• Wi-Fi 6: up to 8 clients over 2.4 GHz, 5 GHz, and 6GHz.

Question 13

Geostationary satellite (GEO)

Answer 13

Fixed position satellite in high orbit. Features: high latency, 30 Mbps speed, not good for real time tasks like gaming, or video call.

Question 14

Low Earth Satellites (LEO)

Answer 14

Faster, closer, but moving satellite. Satellite moves across the sky, lower latency, 70-100 Mbps speed.

Question 15

Global Positioning System (GPS)

Answer 15

Provides location tracking via satellite triangulation. It works by connecting to at least 3-4 satellites.

Question 16

A-GPS

Answer 16

Assisted GPS uses cell towers to estimate position faster.

Question 17

Basic Service Set (BSS)

Answer 17

A single wireless network on a specific channel and frequency band.

Question 18

Dynamic Rate Switching (DRS)

Answer 18

Adjusts data rate based on signal quality

Question 19

Received Signal Strength Indicator (RSSI)

Answer 19

Signal strength as measured at the receiver, using either decibel units or an index value.

Question 20

Signal-to-Noise-Ratio (SNR)

Answer 20

Formula: Signal dBm - Noise dBm = SNR (dB)

Question 21

Basic Service Area (BSA)

Answer 21

The physical space covered by an AP.