Data Transmission
Computer Science: Cambridge International GCSE, topic 1.2.2
Data Transmission
Data transmission is the process of sending data from one device to another.
How is data transmitted?
- Data is sent over a network (like the internet).
- Data is broken down into small units called packets.
- This is more efficient and reliable than sending one large block of data.
- If a packet is lost, only that one packet needs to be resent, not the entire message.
Structure of a data packet
- The header contains the important information needed to get the packet to its destination:
- Destination address (the IP address of where it is going)
- Originator’s address (the IP address of where it came from)
- Packet number (the sequence order of the data)
- The payload is the actual data being sent.
- Example: text, video, image data
- The trailer is the end of the packet.
- It checks for errors during transmission.
Methods of data transmission
- Serial data transmission
- Data is sent one bit at a time over a single channel.
- Reliable over long distances (less chance of data synchronisation errors).
- Slower than parallel transmission.
- Common in USB connections.
- Parallel data transmission
- Data is sent several bits at the same time using multiple channels.
- Much faster over short distances.
- Less reliable over long distances (more data synchronisation issues).
- Used inside computer circuits.
Transmission Directions
Transmission directions describe how data flows between devices: either one-way only, half-two-way but one at a time, or two-way at the same time.
Transmission directions 1
- Simplex data transmission
- Data can be sent in one direction only.
- Simple to implement, requires less bandwidth, but communication is one-way only.
- Used in broadcasting, such as a radio or TV, where there is no need for a return signal.
Transmission directions 2
- Half-duplex data transmission
- Data flows both ways, but only one direction at a time.
- Allows for two-way communication, but is slow for continuous dialogue.
- Used in walkie-talkies, where one person speaks at a time.
Transmission directions 3
- Full-duplex data transmission
- Data can be sent and received in both directions at the same time.
- Fastest method for two-way communication.
- Requires more complex hardware and more bandwidth.
- Used in telephone calls or video conferencing, where both sides can speak and listen at the same time.
Test yourself on Data Transmission
What is the main reason data is broken into packets before transmission?
What is an advantage of full-duplex transmission?