Closed-form solutions for the correlated Rayleigh fading channel capacity under maximum ratio combining(MRC)or selection combining(SC)diversity reception are obtained in this paper.A comparison between the correlated Rayleigh fading channel capacity and independent Rayleigh fading channel capacity is presented.The performance of constant-power adaptive M-ary quadrature amplitude modulation (M-QAM) schemes over correlated Rayleigh channels under MRC or SC diversity reception is investigated.Closed-form expressions for spectral efficiency assuming perfect channel estimation and negligible time delay are derived.