Channel Modeling

Accurate knowledge of the channel over which communication occurs is essential for high data-rate transmission. Channel modelling provides the means for acquiring this knowledge.

H. Nyquist

The modelling of channels was one of the earliest motivating forces behind Communication Theory and Information Theory. The work of Harry Nyquist (1889-1976) for the telegraph transmission line in 1928 formed a foundation of Information Theory. Channel models for telecommunications are used to extract data from the distortions caused by communication environments and to design signals to exploit and counteract environmental distortions. Modelling may be theoretical, where mathematical abstractions are used to characterize environments, or experimental where measurement apparatus is used to test theoretical models and hypothesize new ones. Both theoretical and experimental models are combined in physical devices (modems) which use the Channel Model to improve error performance and data rates. Channel modelling encompasses all telecommunication channels, from wireless indoor to telephone lines, to terrestrial radio and deep-space communications and even quantum communications. Each type of communication medium must be characterized in order to ensure accurate data transmission. Theoretical developments in Channel Modelling have initiated advances in communication applications.

The theoretical work of Harry Nyquist may be credited as one of the pre-requisites of modern digital signal processing within all digital devices -- from mobile handsets to cruise-control in cars. Channel Modelling techniques have also seen significant advances in wired telephony, from echo-cancellation to broadband internet over telephone lines.

Key Research Challenges:

A key challenge for Channel Modelling is to produce parsimonious models which accurately reflect the physical environment while remaining computationally simple and providing intuitive insight into the communication channel. For wireless communication we still do not completely understand the channel behavior. Advances in Channel Modelling will lead to new technologies and have long-term consequences for data transmission. Specific projects may include

Pragmatic codes for channel estimation
Channel model incorporation in code design
Broadband and Ultra-wideband channels
Quantum communication channels
Channels with multiple continuous parameters

More Information

Harry Nyquist biography
3G partnership project Details of mobile and wireless communication channels and standards
Oxford University Research Summary
ADSL demo Simulation of an Asymmetric Digital Subscriber Line ("broadband") modem