Chapter 7 Flashcards
Path Loss
A wireless signal weakens as the distance between the sender and receiver increases.
Interference from other sources
Wireless signals can be distributed by other signals.
Multi-path Propagation
Wireless signals can reflect off objects, causing multiple copies of the signal to arrive at different times, potentially interfering with each other (ex. Echo)
Signal-to-Noise Ratio (SNR)
A high SNR means a clearer conversation, just like a strong signal with minimal interference leads to better wireless communication quality.
But Error Rate (BER)
If you often mishear words in a conversation, it’s similar to but error rate, where data is frequently corrupted during transmission.
Wireless Link Types
- Single-Hop, Infrastructure-Based
- Single-Hop, Infrastructure-Less
- Multi-Hop, Infrastructure-Based
- Multi-Hop, Infrastructure-Less
Single-Hop, Infrastructure-Based
Devices communicate through a central base station (to extend their range)
Single-Hop, Infrastructure-Less
Devices communicate directly without any intermediate infrastructure.
Multi-Hop, Infrastructure-Based
Devices communicate through multiple intermediate nodes and a central infrastructure.
Multi-Hop, Infrastructure-Less
Devices related to data through multiple nodes without any central infrastructure.
Cellular Network Structure
The coverage area is divided into hexagonal cells, each with its own base station (ex. Honeycomb)
Handoff
As you move from one cell to the other, your connection is handed off to the next cell’s base station.
Latency
Like the time it takes for a car to travel from one point to another Lower latency means quicker data transmission.
Jitter
Variation in travel time, similar to unpredictable traffic conditions that cause variable delays.
Wireless Access Point (AP)
Helps devices communicate more effectively by amplifying their “voices” (signals) so everyone can hear (ex. Megaphone)
Stations (STAs)
Devices that communicate over WiFi networks. Each person in the room represents a station.
Wireless Communication Process - Association
When a device wants to join a network, it sends an association request to the AP. The AP responds with an association response, either allowing or not.
Data Transmission
Once associated, devices can send and receive data through the AP.
Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA)
In a wireless network, it’s important to avoid having two devices transmit at the same time to prevent collisions.
Carrier Sense
Before speaking (transmitting data), a device listens to see if anyone else is already “talking”.
Collision Avoidance
If room is quiet, device waits a short, random period before speaking, to avoid starting at the same time as someone else.
MAC Header
Includes the source and destination addresses.
Payload
Actual data being sent.
Trailer
Contains error-checking information to ensure the data was received correctly (similar to repeating a sentence to check for mistakes)
Wired Equivalent Privacy (WEP)
An older, less secure method to protect data.
WiFi Protected Access (WPA)
More secure methods to protect data.
Roaming
When a device moves out of range of one AP and into the range of another, it needs to re associate with the new AP.
Roaming
When a device moves out of range of one AP and into the range of another, it needs to re associate with the new AP.
