Data Transmission (Cambridge (CIE) IGCSE Computer Science)

Revision Note

Robert Hampton

Written by: Robert Hampton

Reviewed by: James Woodhouse

What is data transmission?

  • Data transmission is the process of transferring data from one device to another using a wired or wireless connection

  • Wired data transmission can be completed in two ways:

    • Serial 

    • Parallel

Serial & Parallel Transmission

What is serial & parallel transmission?

  • Serial and parallel are methods of transmitting data (bits) from a sender to a receiver

  • Each method determines how many bits can be transmitted at once

Serial transmission

  • A stream of bits is sent in sequence, one after the other

  • USB is an example of a wired serial connection

Diagram showing serial transmission between sender and receiver

Parallel transmission

  • A stream of bits is sent in sequence, one after the other across multiple wires at the same time

  • Transmission is asynchronous, data does not always arrive at the same time

  • A skew can be caused by data arriving out of order in asynchronous transmission

  • A traditional printer cable is an example of a wired parallel connection

Diagram showing parallel transmission between sender and reciever

Advantages and disadvantages of serial & parallel transmission

Transmission

Advantages

Disadvantages

Serial

  • Reliable over longer distance

  • Cheaper to setup

  • Low interference

  • Slow transmission speed

Parallel

  • Very fast transmission speed

  • Only used on short distances

  • Prone to high interference

Simplex, Half-Duplex & Full-Duplex Transmission

What is simplex, half-duplex & full-duplex transmission?

  • Simplex, half-duplex and full-duplex control the direction in which data is transmitted between a sender and receiver

Simplex transmission

  • Data travels in only one direction

  • Sending data from a computer to a monitor is an example of simplex transmission

Half-duplex transmission

  • Data can travel in both directions, but not simultaneously (bi-directional) 

  • A printer cable which waits for the data to be received before sending back a ‘low ink’ message is an example of half-duplex transmission

Full-duplex transmission

  • Data can travel in both directions at the same time (bi-directional)

  • Network cables can send and receive data at the same time and are examples of full-duplex data transmission

  • Full-duplex is used in local and wide area networks

Advantages and disadvantages of simplex, half-duplex & full-duplex transmission

Transmission

Advantages

Disadvantages

Simplex

  • Cheap as only one wire is used

  • Slow

  • Expensive for bi-directional transmission (multiple wires)

Half-duplex

  • Cheaper than simplex for bidirectional transmission (fewer wires)

  • Slow

Full-duplex

  • Fast as data can travel in both directions simultaneously

  • Expensive

  • Wires can be combinations of serial, parallel, simplex, half-duplex and full-duplex

Simplex

Half-duplex

Full-duplex

Serial

Serial-Simplex

Serial-Half-duplex

Serial-Full-duplex

Parallel

Parallel-Simplex

Parallel-Half-duplex

Parallel-Full-duplex

  • Serial-Simplex

    • Data is transmitted one bit at a time in a single direction on one wire

  • Serial-Half-duplex

    • Data can be transmitted in both directions on a single wire but only one bit at a time can be transmitted in one direction at a time

  • Serial-Full-duplex

    • Data can be transmitted in both directions at the same time on a single wire one bit at a time 

  • Parallel-Simplex

    • Multiple wires transmit one bit at a time in one direction

  • Parallel-Half-duplex

    • Multiple wires send multiple bits of data in both directions but only one direction at a time

  • Parallel-Full-duplex

    • Multiple wires send multiple bits of data in both directions at the same time

Worked Example

A company has a website that is stored on a web server
The company uses parallel half-duplex data transmission to transmit the data for the new videos to the web server.

Explain why parallel half-duplex data transmission is the most appropriate method.

[6]

Answer

  • Parallel would allow for the fastest transmission [1]

  • as large amounts of data [1]

  • can be uploaded and downloaded [1]

  • but this does not have to be at the same time [1]

  • Data is not required to travel a long distance [1]

  • Therefore, skewing is not a problem [1]

Examiner Tips and Tricks

Any four of these points qualifies as a full answer, however make sure your answer is cohesive.

Saying “Parallel would allow for the fastest transmission but this does not have to be at the same time” would qualify as one mark as only the first part makes sense and follows logically

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Robert Hampton

Author: Robert Hampton

Expertise: Computer Science Content Creator

Rob has over 16 years' experience teaching Computer Science and ICT at KS3 & GCSE levels. Rob has demonstrated strong leadership as Head of Department since 2012 and previously supported teacher development as a Specialist Leader of Education, empowering departments to excel in Computer Science. Beyond his tech expertise, Robert embraces the virtual world as an avid gamer, conquering digital battlefields when he's not coding.

James Woodhouse

Author: James Woodhouse

Expertise: Computer Science

James graduated from the University of Sunderland with a degree in ICT and Computing education. He has over 14 years of experience both teaching and leading in Computer Science, specialising in teaching GCSE and A-level. James has held various leadership roles, including Head of Computer Science and coordinator positions for Key Stage 3 and Key Stage 4. James has a keen interest in networking security and technologies aimed at preventing security breaches.