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Link adaptation (LA) can significantly increase the spectral efficiency and meantime provide services of various qualities, both of which are highly desirable in today's high-speed communication systems. However how to perform precise switching optimally in practical systems involving non-flat fading channels and several adaptive techniques is seldom treated. We therefore investigate this problem and propose a general optimal switching scheme. This paper gives a framework of such a scheme for link adaptation and a detailed designing procedure. We present a vigorous proof of the optimality condition and show that the optimal switching boundaries have a linear relationship, which is independent of coding, modulation and channels. Also, we extend this scheme to multicarrier, MIMO and multiservice systems to ensure global optimality. With low complexity, optimality, and generality the proposed general …