Previous works on maximum ratio combining (MRC) diversity have derived a closed-form cumulative distribution function (CDF), referred to as Lee's formula, for spatially correlated Rayleigh fading channels. It is usually believed that (due to its singularity) Lee's formula will result in large numerical error when two eigenvalues of a diversity antenna's covariance matrix are close to each other. This letter shows that the limit of Lee's formula converges to the true CDF as eigenvalues converge to each other, which implies that Lee's formula is robust in determining diversity gains of arbitrary antennas based on stochastic measurements.
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