Data communication and capacity

Data communication is the exchange of data between connected devices over a transmission medium, such as a cable or radio waves.

Every data communication has five components:

• the sender, which sends the data;
• the receiver, which receives it;
• the message, the data itself (text, numbers, images, audio, video);
• the transmission medium, the path it travels along;
• the protocols, the agreed rules that both sides follow.

Two measures describe how much a channel can carry:

• Bandwidth is the range of frequencies a channel can carry: maximum frequency − minimum frequency, measured in hertz (Hz). 1 KHz = 1000 Hz, and 1 MHz = 1000 KHz = 10⁶ Hz.
• Data transfer rate (or bit rate) is the number of bits sent per second, in bps. The book counts in steps of 1024: 1 Kbps = 1024 bps, 1 Mbps = 1024 Kbps, and so on.

Watch the capital letters: MBps means megabytes per second, while Mbps means megabits per second. Since a byte is 8 bits, 1 MBps is eight times faster than 1 Mbps.