2.1 Data Transmission Flashcards
Data transmission
The movement of data via a transmission medium between the sender and the receiver
Simplex data transmission
Data travels in one direction only
Half-duplex data transmission
Data can travel in both directions along a single cable, but not simultaneously
Full-duplex data transmission
Data can travel in both directions simultaneously using 2 cables
3 types of cable & their uses
- Twisted pair cable (eg. Ethernet cable)
- Coaxial cable (eg. television, electrical equipment)
- Fibre-optic cable (eg. Internet cables)
Serial data transmission
Application
Data is sent 1 bit at a time over a single wire
Application: connect computer to a modem
Parallel data transmission
2 applications
1 byte of data is sent down 8 wires at the same time
Applications:
- sending data from a computer to a printer
- internal data transfer (buses)
4 advantages of serial data transmission
- SINGLE WIRE means there is less chance of interference/data corruption
- SINGLE WIRE reduces costs
- MORE reliable over greater distances
- bits will still be synchronised after transmission
Disadvantage of serial data transmission
Slower rate of data transmission
Advantage of parallel data transmission
Faster rate of data transmission
2 disadvantages of parallel data transmission
- More expensive
- Less reliable over long distances (bits can become ‘skewed’ where signals travel at different speeds due to differences in wires and may not all arrive at the same time)
5 advantages of asynchronous transmission
- Cheaper
- If character is corrupted during transmission, successor & predecessor characters are not affected
- Possible to transmit signals from sources with different bit rates
- Transmission can start as soon as data byte is available
- Easy to implement
2 disadvantages of asynchronous transmission
- Slower, less efficient
2. Successful transmission depends on recognition of start bits, which can be missed/corrupted
Advantage of synchronous transmission
Faster
2 disadvantages of synchronous transmission
- Costly (needs local buffer storage to assemble blocks; needs accurately synchronised clocks at both ends)
- Complicated (sender & receiver have to operate at same clock frequency)
6 pros of using USB
- Devices plugged into computer are automatically detected
- USB connectors are shaped so that it is impossible to install devices incorrectly
- Has become the industry standard; considerable support available to users
- Supports multiple data transmission speeds
- Latest USB standards are backward compatible with older standards
- Faster transmission compared to wireless
3 cons of using USB
- Cable length is limited to 5m
- Transmission speed limited to 480Mbps
- Older USB standard may not be supported in the near future
Integrated Circuit (IC)
An IC is a collection of microscopic electronic circuits, sealed into a plastic/ceramic package
*uses parallel data transmission
When might a parity check not identify that a bit has been transmitted incorrectly?
- Even number of digits are changed
- A transposition error has occurred
Explain how Automatic Repeat reQuests (ARQ) are used in data transmission and storage.
- It’s an error detection method
- Uses acknowledgement and timeout
- Request is sent (with data) requiring acknowledgement
- If no acknowledgment within certain time frame data package is resent
- When data received contains an error a request is sent (automatically) to resend the data
- The resend request is repeatedly sent until packet is received error free
