Communication Technology Terms

Communications technology has transformed our lives.

Communication technology propelled humanity into the digital information age. Manifested by the omnipresence of wireless mobile devices, high-definition TV and other broadband multimedia services that consumers take for granted, technology continues to improve. Yet the fundamental laws discovered over 60 years ago, still underpin technology today and have unveiled multiple universal applications.

History

Considered the founding father of modern information theory, Claude E. Shannon's discovery is often called communication theory. In his landmark 1948 paper, "A Mathematical Theory of Communication," Shannon laid out the basic model and system concepts, which characterized information in terms of mathematical probabilities that can be quantified and measured. The notion that virtually error-free communication can be facilitated over a noisy channel with efficient coding techniques is a key contribution of information theory.

Communications Channel

In Shannon's communication model, the communication channel is the physical medium through which information messages are transmitted between sender and receiver. A twisted copper pair, coaxial cable, fiber optic cable and the wireless radio frequency spectrum all constitute a channel.

Bandwidth

Bandwidth is one factor that affects information transfer rate over a communication channel and is designated as a frequency range in kilohertz or megahertz. For example, WiFi signals have a much wider bandwidth than narrowband AM radio. Comparing the information payload capacity of the two in terms of bandwidth, the former lies on the scale of a tractor-trailer rig while the latter is like a compact car.

Noise

Noise is inherent to any communications system and can originate from natural or man-made sources. Examples include radio-frequency interference from electronic devices, static from lightning and electrical equipment and electromagnetic interference from sun spot activity. Noise introduces errors and alters the original form of the message by the time it reaches its destination.

The strength of the message signal relative to noise, also known as the signal-to-noise (S/N) ratio, is another key aspect that affects the speed of information transfer. Imagine having a conversation in a quiet restaurant and then at a wild sporting event. In the second case, you need to repeat yourself several times because the noise of the crowd overwhelms the message.

Channel Capacity

Information theory defines channel capacity as the maximum rate at which information can be transmitted through a channel, measured in bits per second or kilobits per second. Channel capacity is a function of both bandwidth and signal-to-noise ratio and one can be exchanged for the other. Decreasing bandwidth and boosting S/N ratio can preserve channel capacity. However, Shannon's information theory further states that efficient message and channel coding techniques also play key roles in establishing theoretical limit.

References

• ATT: A Mathematical Theory of Communications
• Standford: Communication in the Presence of Noise
• Bell Labs: Claude Shannon, Father of Information Theory
• University of Capetown: Channel Capacity
• Harvard University: Signal, Noise, Bandwidth, and Channel Capacity