A Level AQA 4.9 Fundamentals of communication and networking | 4.9.1 Communication and 4.9.2 Networking

What is serial data transmission

Bits are sent one after another along the same line

Examples of serial data transmission

• Mouse joystick

• Modem link

What is parallel data transmission

Several bits are sent simultaneously along sperate lines or channels

(Faster but with drawbacks)

Examples of parallel data transmission

• Local printer

• Scanner

• Hard drive

Two problems with parallel data transmission

• Skew

• Crosstalk

What is skew

As every wire has slightly different properties, hence meaning bits travel at slightly different speeds

What is corsstalk

Refers to electromagnetic interference between two adjacent channels or parallel wires.

It gets more pronounced as the frequency increases

Why do these issues of Skew and Crosstalk’s occur

As data gets sent across multiple lines

Serial VS Parallel transmission

(Parallel Faster but with drawbacks so good for short range serial the opposite)

Synchronous transmission

All data transfers are timed to coincide with an internal clock pulse.

(The data is sent as one long stream or block data, with no gaps in the transmission. The receiver counts the bytes to reconstruct the bytes)

Asynchronous transmission

Each byte is sent separately the moment it is available instead of waiting for a clock signal

The parity bit

It is added as the 8th bit as a form of error detection

(Odd ore even parity bits could be used )

Synchronous vs Asynchronous transmission

Image talks about asynchronous

for synchronous just say the opposite of asynchronous

Define Baud rate

Is the number of signal changes per second in a communication channel.

Define Bit rate

Ss calculated as baud rate × number of bits per signal unit.

Define Bandwidth

Is the range of frequencies available for data transmission.

Define Latency

The time delay between the moment the first byte or packet of a communication starts and when it is received at its destination.

Define Protocol

The set of rules relating to communication between devices

List examples of what the protocol needs to define

• Standards of physical connections and cabling

• The rate of transmission (bit rate or baud rate)

• Data format

• Whether transmission is synchronous or asynchronous

The differences between Baud rate and Bit rate

Baud rate differs from bit rate, as bit rate considers the number of bits transmitted while baud rate does not.

The relationship between Bit rate and bandwidth

Bit rate is directly proportional to bandwidth in a communication channel.

(So higher bandwidth means more bits are allowed to be transmitted per second, increasing data transfer speed.)

What is a computer network

A system of interconnected devices that share resources and data. Networks can be wired or wireless and vary in scale

Physical star topology

Each device on the network is connected to a central communication device, such as a Hub or a Switch

Logical bus network topology

One cable connects every device to the network. This is called the backbone. At each end a device called the terminal is placed at each ends this is done to absorbs the signals when they reach the end, to prevent interference.

Pros of a Physical star topology

• Improved security and speed -Use of a switch improves the security and speed of a star network (not every deceive can see or intercept other packets)

• Increased reliability -The switch or hub is a central point of failure, so if one workstation fails the entire system wont fail.

• It is easy to add and remove clients to and from the network.

Cons of a Physical star topology

• Expensive to install thanks to the amount of cable required.

• Should the central hub fail, all communication over the network is stopped.

Pros of a Logical bus network topology

• There is no central hub, reducing the chances of a network failure

• Cheaper to set up due to not having a central hub and less cable is used

Cons of a Logical bus network topology

• Should the backbone fail, the entire network becomes unusable.

• The backbone is used for communication by multiple clients, introducing the risk of collisions.

• Packets are sent through the shared backbone, allowing every client on the network to see packets that aren’t intended for them

How does a Physical star topology operate with a hub

Network signals that reach the hub are sent out to all connected devices. The hub does not process the signals that pass through it, but just repeats them on all of its connections.

How does a Physical star topology operate with a switch

Uses a table that maps each device to the port it is connected to. In this way, the switch is able to direct messages to the correct recipient (receiving device).

How does a Logical bus network topology operate

Network signals travel through a main cable to all connected devices. Each message includes a destination address linked to a device's MAC address. The intended recipient processes the message, while others ignore it.

(Messages travel via a main cable, with the destination's MAC address ensuring only the intended device responds.)

What is peer to peer networking (P2P)

Networks are decentralized but can be less efficient for large-scale use

Allows devices to share resources without a central server

What is client server networking

Centralized control improves security and resource management.

Has dedicated servers providing resources to client devices.

What does LAN stand for

Local Area Network

What is a LAN

Covers a small geographic area, such as a home or office (e.g. Wi-Fi)

What does WAN stand for

Wide area network

What is a WAN

Spans large geographic distances, connecting multiple LANs (e.g the internet)

What does WLAN stand for

Wide Local Area Network

What is WLAN

Uses radio waves instead of physical cables to connect devices. (More convenient but are less secure than wired LANs)

What is WiFi

A wireless local area network that is based on international standards. And connects devices to a network using radio waves

What are the common frequency bands WiFi operates on

It typically operates on 2.4GHz and 5GHz frequency bands.

2.4GHz vs 5GHz

• 2.4GHz has longer range but lower speed

• 5GHz offers faster speed with shorter range

Identify the components required for wireless networking.

Wireless network adapter and wireless access point.

What is a Wireless network adapter

A physical device that allows a computer system to connect to a wireless network.

What is a Wireless access point.

Uses a radio transceiver (so radio waves) to allow wireless connections to a network

Describe how wireless networks are secured.

Through strong encryption methods like WPA/WPA2, disabling SSID broadcast, and implementing MAC address filtering.

Explain the wireless protocol Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) with and without Request to Send/Clear to Send (RTS/CTS).

CSMA/CA is a network protocol that listens to a network channel before transmitting to avoid collisions. With RTS/CTS, a device sends a request to send before transmitting, and waits for a clear to send signal, further reducing collision risk.

Explain the purpose of Service Set Identifier (SSID).

SSID is the name assigned to a WiFi network, allowing devices to distinguish between different networks.