Nearfar

Nearfar is a term used in wireless communications and electromagnetics to describe phenomena that arise from differences in signal strength between nearby and distant transmitters, and to distinguish the near-field and far-field regions around antennas. In telecommunications, the near-far problem refers to a specific interference issue in code-division multiple access (CDMA) systems where a user close to the base station transmits at higher power than a distant user. Because all users share the same spectrum and are multiplexed by spreading codes, the strong signal from the near user can raise the interference floor for the far user, degrading its signal quality.

Mitigation strategies include tight uplink power control so that mobile stations adjust transmit power to achieve a target received power at the base station, as well as soft or hard handoffs, scheduling, and advanced multiuser detection or interference cancellation at the receiver. Modern networks also employ adaptive antenna techniques and beamforming to separate signals spatially and reduce near-far effects.

In electromagnetics, the term near field and far field describe zones around an antenna. The near field is close to the radiating element where reactive energy dominates and the field does not resemble a propagating wave, while the far field is at greater distances where radiated fields behave like traveling waves and the angular field pattern becomes stable. Boundaries between these regions depend on frequency and antenna size and are characterized by rules of thumb such as distance scales on the order of a wavelength or more.

Overall, nearfar encompasses both interference-related challenges in wireless networks and the fundamental transition from reactive to radiating fields in antenna theory.