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Bit error rate (BER)-based constrained optimization of average spectral efficiency for adaptive Multi-level Quadrature Amplitude Modulation (MQAM) with service rate and power constraint is studied under composite Gamma-Lognormal fading channel condition. We obtain the corresponding optimal schemes for power and rate adaptation for continuous and discrete rate MQAM. The optimal power for continuous rate QAM is shown to be a combination of two functions; one of which with water-filling nature and the other proportional to log(1/BER), whereas for discrete rate QAM the solution is proportional to log(1/BER) over each rate region. We have also shown that transmission rate is a monotonically increasing function of BER.