In radio communication environment, the TX signals tend to be affected by the shadow fading, buildings,
and landforms. The TX signals from the MS arrive at the BTS through various paths, such as
line-of-sight (LOS), reflections, and dispersions. As the MS moves around, Rayleigh fading occurs when
the TX signals passing through various ways are combined.
To suppress Rayleigh fading, four-way receive diversity is implemented in the TRX board, that is, four
receive paths receive the same signal separately. Then, the four RX signals are combined into one
according to the specified algorithm. In this way, a strong useful signal is obtained, and the uplink gain is
enhanced. To ensure that the diversity antennas receive signals separately from each other, the distance
between diversity antennas must be greater than 10 times the radio signal wavelength or the polarization
diversity is adopted.
Four-way receive diversity helps to suppress Rayleigh fading and provide better signal quality on the
uplink, thus improving the quality of service (QoS). In addition, four-way receive diversity can be used to
improve the uplink performance in wide coverage scenarios.

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