KS3, GCSE, A-Level Computing Resources
Wireless networks utilize radio waves for communication. These networks are "wireless" because they operate without physical cables. Devices in wireless networks have antennas or sensors that enable communication using electromagnetic waves or infrared waves. Wireless networks offer greater flexibility and enable mobility, which is advantageous in situations where physical connections are inconvenient or not feasible.
Wi-Fi is a wireless networking protocol that allows devices to communicate without direct cable connections. It represents a type of wireless local area network (LAN) based on the 802.11 IEEE network standard.
From the user's perspective, Wi-Fi provides internet access from wireless-capable devices like phones, tablets, or laptops. Most modern devices support Wi-Fi, allowing them to join networks for internet access and resource sharing.
Wi-Fi Logo:
Advantages:
Disadvantages:
Wi-Fi Network Connected to the Internet:
Bluetooth is a wireless technology that enables the exchange of data between different devices within a short distance by creating a Personal Area Network (PAN).. Some common uses include, pairing mobile devices with other devices (e.g., earbuds, cars, smart fridges) and connecting devices like printers or mice to computers.
Bluetooth uses a radio technology called frequency hopping spread spectrum (FHSS), that has a maximum data rate of 24mbps. Data is broken down into chunks and then transferred on up to 79 frequencies.
Advantages:
Disadvantages:
Bluetooth PAN:
Wireless networks are often considered less secure than wired networks due to several factors:
To enhance security for wireless networks, consider the following measures for both home and office setups:
CSMA/CA:
RTS/CTS:
The described protocol aims to prevent collisions on a data channel. However, due to the issue of “hidden nodes,” it cannot always achieve collision avoidance. Instead, it relies on acknowledgments to confirm successful data arrival.
Before transmitting, a node listens for signals on the wireless network to check if another node is currently transmitting. If a signal is detected, the node waits for a random period before checking again.
Despite these efforts, data collisions can still occur. For instance, two nodes might transmit simultaneously when they both sense an idle channel. In such cases, the receiver won't send an acknowledgment back to the sender.
To address this challenge, the protocol employs a mechanism called RTS/CTS (Request to Send/Clear to Send) to overcome both the hidden nodes problem and collision issues.
When a station intends to transmit data and confirms that no other node is currently transmitting, it sends a Request to Send (RTS) signal. The Wireless Access Point (WAP) responds with a Clear to Send (CTS) signal when the channel is idle. This mechanism addresses the issue of “hidden nodes,” where a node is audible to the WAP but not to the transmitting node itself.
Consider the scenario depicted in the diagram to the right: Nodes A and C can both communicate with the WAP at B, yet they remain hidden from each other during transmission.
A's red circle does not reach C, and C's green circle does not reach A.
Revised CSMA/CA RTS/CTS flowchart algorithm
