Maximum-ratio combining (MRC) is a simple and effective combining scheme for adaptive antenna arrays to combat fading.However

it requires estimation of the spatial signature (i.e.

the channel gain and phase at each antenna element) of the desired signal across the array.Assuming the channel estimation is obtained by

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symbols' correlation using common pilot channel (CPICH)

we proceed to develop a fully analytical assessment of the impacts of Gaussian error and Doppler spread on the MRC performance.The originality of the approach revolves around the derivation of the closed-form expression for average bit error probability for coherent BPSK.The expression is then applied to find the optimal correlation length of channel estimation.As a result

the computing method of optimal correlation length has been given.It is a

lso proved that the optimal correlation length

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was only correlative with maximal Doppler spread

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d

and symbol duration.