Data communication and networking

Data communication is the transfer of digital information from one device to another over some physical medium. At its heart lies a simple challenge: a string of binary digits must be turned into signals that can travel along a copper wire, an optical fibre or a radio link, and then be reconstructed accurately at the far end. The study of data communication is largely concerned with how this is done reliably, efficiently and at the speeds modern applications demand.

Several ideas recur throughout the field. Data may be sent serially, one bit after another along a single path as in the RS-232 and RS-485 standards, or in parallel over several paths at once. The bits are represented using an encoding scheme that defines how ones and zeros map onto signal levels or transitions, chosen so that the receiver can recover the timing and the data. Because no real link is perfect, error detection methods such as cyclic redundancy checks add extra bits that let the receiver notice when data has been corrupted, and forward error correction goes further by allowing some errors to be repaired without retransmission.

These principles underlie the networks people use daily. Local area networks, commonly built on Ethernet, connect computers within a building, while wide area links and internet access technologies such as ADSL and ISDN carry data over the telephone network and beyond. The transmission medium matters too: copper cable is cheap and familiar, while optical fibre carries far more data over longer distances with less interference. Wireless networks add mobility by replacing the cable with radio. Together these elements form the foundation of how computers exchange information.

Frequently asked questions

What is the difference between serial and parallel transmission?

Serial transmission sends bits one after another along a single path, while parallel transmission sends several bits at once over multiple paths. Serial links are simpler and common over distance.

Why is error detection needed?

No physical link is perfect, so data can be corrupted in transit. Methods such as cyclic redundancy checks add extra bits that let the receiver detect when this has happened.

How does fibre differ from copper cable?

Optical fibre carries data as light and can transmit much more information over longer distances with less interference than copper cable, though it is generally more costly to install.