Data Transmission

Data Transmission

Learning Objectives

Understand transmission modes Understand transmission media

Communication System Requirements

There are 5 requirements for digital communication systems:

• sender
• receiver
• transmission medium (WiFi, twisted pair, co-axial, fibre-optic, satellite)
• message
• protocol (HTTP(s), FTP, SMTP, POP3, IMAP, ethernet etc)

Transmission Media

Click the hotspots to find out more

Transmission Modes

Data can be sent via the medium in 3 different ways:

• Simplex: data flow in one-way only
• Half-duplex: data flow is bi-directional, but not simultaneously
• Full-duplex: data flow can be bi-directional and simultaneous

Transmission Key Terms

Bandwidth: a measure of the amount of data that can be transmitted per second (usually in Mb/s or Gb/s) Attenuation: the rate at which the strength/intensity of the signal decreases

Wifi

Works by transmitting data over radio waves Different channels (frequencies) used to reduce interference

Wifi: Channels

To solve issues with interference, frequencies can be broken down into separate channels To reduce interference, different networks & devices should communicate on different channels Bandwidth utilisation is also increased – data can be sent on quiet rather than congested channels

Wireless Frequencies

5G has a higher frequency than 4G – this is why it has a higher bandwidth, but has a shorter range and is more likely to get blocked by walls etc. There are also arguments about higher frequencies causing health issues

Advantages and Disadvantages of Wifi

• Lower bandwidth
• Less secure than cables – anyone can listen in (though data should ideally be encrypted)
• High absorption rate (e.g. blocked by walls)
• Short range (20 to 150m)

• Accessible with portable devices (laptops, tablets, phones etc)
• No cables required
• Setup is easy/fast
• Suitable for public locations – cafes, hotels, transport etc

Task

Scroll to the bottom of the Canvas page to find this week's task. You can use internet resources (and AI as long as you able to represent the answers in your own words) to help find the answers.

Twisted Pair

Transmits data using electrical signals over pairs of copper wires that are twisted together. The twisting cancels out noise and crosstalk from adjacent pairs, improving signal quality over distance. The most common cable type for modern Local Area Networks (LANs), often called Ethernet cable (e.g., Cat 5e, Cat 6). Also used for traditional telephone lines (DSL).

Satellite

Data is transmitted as microwave radio signals from an Earth station (ground transceiver) to a satellite in orbit. The satellite amplifies and retransmits the signal back to a different Earth station. Global internet/data links in remote areas (where cables are impractical), long-distance telephone calls, military communications, and broadcasting TV signals over vast geographical regions.

Coaxial

Transmits data using electrical signals over a central copper wire. This wire is surrounded by a layer of insulation, a metal foil shield, and an outer jacket to reduce electromagnetic interference (EMI). Historically used for Local Area Networks (LANs), but now primarily used for cable television (CATV) distribution and connecting modems to the local Internet Service Provider (ISP) line.

Fibre Optic

Transmits data using pulses of light sent down thin strands of glass or plastic fiber. Light signals are not affected by electrical interference, allowing for extremely high speeds and very long transmission distances. High-capacity, long-distance links like Internet backbones, connections between major cities and countries (undersea cables), and modern high-speed broadband connections (Fibre to the Home/FTTH).