Adaptive modulation with power constraint in SC-FDE

Based on the concept of optimal signal subspace, signal spectrum transformation is carried out according to channel state information before transmission, and system performance can be improved considerably. In this paper, we propose an adaptive modulation algorithm that guarantees a desired bit error rate with uniform power allocation, and the algorithm has low complexity and high spectrum efficiency. Our approach is novel in that we optimize both bit allocation and power allocation to maximize spectral efficiency under the constraint of power and bit error rate. The new adaptive modulation algorithm can greatly improve system performance without increasing system complexity significantly.