equalgain

Equalgain, in the context of wireless communications, refers to equal-gain combining (EGC), a diversity technique used to coherently combine signals from multiple receive paths. It is one of the classic diversity methods, alongside maximal-ratio combining (MRC) and selection combining (SC), and is valued for offering a good balance between performance and implementation complexity.

In EGC, the receiver aims to align the phases of the signals from all branches and apply equal amplitude weighting before summing. Practically, the receiver estimates the complex channel gains on each branch, compensates the phase of each received signal to make them in phase, and then sums the branches with unit (or equal) gain. The result is a combined signal that benefits from constructive interference across branches without performing amplitude-based weighting.

Compared with MRC, which weights each branch by the conjugate of its channel gain (including magnitude), EGC uses equal magnitudes and primarily adjusts phases. This makes EGC simpler to implement in some receivers while still delivering substantial diversity gains. EGC often approaches the performance of MRC at moderate signal-to-noise ratios but can be more sensitive to phase estimation errors and phase noise, particularly in fast fading environments.

Applications of equal-gain combining appear in mobile and wireless systems, including OFDM and cooperative diversity setups, where multiple antennas or relay paths are available. It is also used in software-defined radios as a practical compromise between complexity and performance.

See also: maximal-ratio combining, selection combining, diversity techniques, fading channel.