A time division duplexing (TDD) system operates half-duplex on a single channel, creating the illusion of full-duplex communication by rapidly switching back-and-forth between transmit and receive.
It consists of a combination of leakage (the signal traveling directly from the transmitter to the receiver) and local reflections.
In addition, transmitter components (such as mixers and power amplifiers) introduce non-linearities that generate harmonics and noise.
Finally, the self-interference cancellation solution must detect and compensate for real-time changes caused by temperature variations, mechanical vibrations, and the motion of things in the environment.
The precise amount of cancellation required will vary depending on the power of the transmit signal that is the source of the self-interference and the signal-to-noise ratio (SNR) that the link is expected to handle in half-duplex mode.
Both the analog and digital cancellers consist of a number of “taps” composed of attenuators, phase shifters, and delay elements.
The signal on the transmit frequency, known as the blocker, may be so strong that it desensitizes a receiver listening on an adjacent channel.
[5][6] SIC enables satellite repeaters to extend coverage to indoor, urban canyon, and other locations by reusing the same frequencies.
Likewise, the indoor-facing radio listens for indoor users and must be isolated from the transmitter repeating their signals to the satellite.
Cable Labs developed the Full Duplex DOCSIS 3.1 standard to enable symmetrical service at speeds up to 10 Gbit/s in each direction.
The headend must support simultaneous transmission and reception across the full duplex band, which requires SIC technology.
SIC can enable wireless mesh nodes to reuse frequencies so that the data is retransmitted (relayed) as it is received.
Most tri-band routers use the same pair of 80 MHz channels (at opposite ends of the 5 GHz band) to minimize interference.
The military frequently requires multiple, high power radios on the same air, land, or sea platform for tactical communication.
These new capabilities have been recognized as a potential 'superpower' for armed forces that may bring about a paradigm shift in tactical communications and electronic warfare.
Spectrum sharing is a topic of great interest to the mobile phone industry as it begins to deploy 5G systems.
Radios that dynamically select idle channels to make more efficient use of finite spectrum resources are the subject of considerable research.