2.1.2 METHODS OF DATA TRANSMISSION

Topics from the Cambridge IGCSE (9-1) Computer Science 0984 syllabus 2023 - 2025

OBJECTIVES
(a) Describe how data is transmitted from one device to another using different methods of data transmission.
(b) Explain the suitability of each method of data transmission, for a given scenario​.

ALSO IN THIS TOPIC
2.1.1 METHODS OF DATA TRANSMISSION
YOU ARE HERE | 2.1.2 METHODS OF DATA TRANSMISSION
2.1.3 METHODS OF DATA TRANSMISSION
2.2 METHODS OF ERROR DETECTION
2.3 ENCRYPTION
TOPIC 2 KEY TERMINOLOGY
TOPIC 2 ANSWERS
TOPIC 2 TEACHER RESOURCES (CIE)

---

PARALLEL Vs SERIAL TRANSMISSION

Parallel transmission is where bits can be sent parallel to each other through separate cables or tracks on a circuit board, it is very fast to send data via this method however it comes with problems especially when data is transmitted of any more than a short distance. Parallel transmission is mainly used within computer systems and components on a circuit board level, whereas serial transmission is mainly used between components and computers.
Early computers had 8 tracks on the circuit board to carry 8 bits in parallel, this has increased and currently 64 tracks to carry 64 bits in parallel is very popular.

The problem with parallel transmission is that each bit needs to arrive at the same time, any latency within one bit arriving causes problems, latency could be caused by any discrepancy in the properties of the cables, tracks or data carrying medium or electromagnetic interference.

Serial transmission is where bits are sent one after the other, for example through a copper cable bits are sent one after the other and are represented by an electrical signal in the form of a particular voltage or change in voltage depending on the system.

MULTIPLEXING, SIMPLEX,  HALF-DUPLEX AND DUPLEX
Multiplexing is the process of managing various signals between devices, three common methods of doing this are 'simplex', 'half-duplex' and 'duplex'

SIMPLEX
Simplex is when data can only be sent from its source in one direction. For example a radio station simply send out the signal, the signal cannot be received by the radio transmission hardware

HALF-DUPLEX
Half-Duplex is where a signal can be both sent and received but not both at the same time. An example of this is a walkie-talkie, only one person can talk at any time, the handheld units cannot both send and receive a signal at the same time.

DUPLEX
Duplex is where data can be both send and received at the same time. An example of this could be using the telephone where you can both talk and listen at the same time. Cables frequently carry signals in both directions and as long as they are out of phase the signals will not interfere with each other.

FULL DUPLEX
Full-duplex transmission is a method of transmitting data in both directions simultaneously, over separate communication lines. This method is suitable for scenarios where data needs to be transmitted in both directions at the same time, and where a high-bandwidth connection is required. For example, full-duplex transmission can be used for communication between two computers in a local area network (LAN), where both computers can send and receive data at the same time.

THE SUITABILITY OF EACH METHOD FOR A GIVEN SCENARIO

1. Serial transmission: Serial transmission is a method of transmitting data one bit at a time, over a single communication line. This method is suitable for scenarios where data is being transferred over long distances, it is slower than parallel data transmission. For example, serial transmission can be used for the transmission of data between a computer and a printer, or for the control of a simple device, such as a robot.
2. Parallel transmission: Parallel transmission is a method of transmitting multiple bits of data simultaneously, over multiple communication lines. This method is suitable for scenarios where high data transfer rates are required, such as for the transfer of large amounts of data between the cpu and the RAM. Parallel transmission can be faster than serial transmission, but requires more complex hardware and cabling or tracks on the PCB (Printed Circuit Board).​

​ADVANTAGES AND DISADVANTAGES OF EACH METHOD

SERIAL TRANSMISSION
Advantages:

• Simple hardware and cabling
• Low cost
• Low power consumption
• Suitable for long-distance communication

Disadvantages:

• Slow data transfer rate
• Limited bandwidth
• Not suitable for large amounts of data

PARALLEL TRANSMISSION
Advantages:

• High data transfer rate
• Suitable for large amounts of data
• More efficient than serial transmission

Disadvantages:

• Complex hardware and cabling
• Higher cost
• Higher power consumption
• Limited maximum cable length

SIMPLEX TRANSMISSION
Advantages:

• Simple hardware and cabling
• Suitable for one-way communication
• No need for a return channel

Disadvantages:

• Data can only be transmitted in one direction
• Limited to simple communication scenarios
• Not suitable for bidirectional communication

HALF-DUPLEX TRANSMISSION
Advantages:

• Data can be transmitted in both directions
• Suitable for limited bandwidth scenarios

Disadvantages:

• Data can only be transmitted in one direction at a time
• Not suitable for high-bandwidth communication
• More complex than simplex transmission

DUPLEX TRANSMISSION
Advantages:

• Data can be transmitted in both directions simultaneously
• Suitable for bidirectional communication
• More efficient than half-duplex transmission

Disadvantages:

• Limited by the bandwidth of a single communication line
• Not suitable for high-bandwidth communication

FULL-DUPLEX TRANSMISSION
Advantages:

• Data can be transmitted in both directions simultaneously, over separate communication lines
• Suitable for high-bandwidth communication
• More efficient than duplex transmission

Disadvantages:

• More complex hardware and cabling
• Higher cost
• Higher power consumption

1. What is serial transmission and when is it used?
2. What is parallel transmission and what are its advantages and disadvantages?
3. What is simplex transmission and what type of communication is it best suited for?
4. What is half-duplex transmission and how does it differ from full-duplex transmission?
5. What is duplex transmission and what are its benefits?
6. How does full-duplex transmission improve communication compared to half-duplex transmission?
7. What are the key differences between serial and parallel transmission?
8. Can data be transmitted in both directions using simplex transmission?
9. What are some practical applications of duplex transmission?
10. When would parallel transmission be preferred over serial transmission?

ALSO IN THIS TOPIC

2.1.1 METHODS OF DATA TRANSMISSION | Data Packets
2.1.2 METHODS OF DATA TRANSMISSION | Serial, Parallel, Simplex, Duplex
2.1.3 METHODS OF DATA TRANSMISSION | The Universal Serial Bus
2.2 METHODS OF ERROR DETECTION | Parity Checks, Check Sum, Check Digit, ARQ
2.3 ENCRYPTION | Symmetric and Asymmetric Encryption
TOPIC 2 KEY TERMINOLOGY
TOPIC 2 ANSWERS
TOPIC 2 TEACHER RESOURCES (CIE)