Optimizing power and resource management for multiuser MIMO/OFDM systems

Fast adaptive transmission has been recently recognized as an essential method to exploit the system diversity and enhance power/spectral efficiency in time-varying channels. In this paper, we propose adaptive transmission algorithms for multiuser MIMO/OFDM systems. The algorithms adaptively control multiple-access, modulation, and transmit power to exploit the channel variation in space, frequency, and user domains. The ultimate objective is to optimize the overall power efficiency while ensuring the fulfillment of every user´s QoS requirements. A major challenge in the problem lies in the optimization complexity due to the presence of non-linear, non-convex constraints. The proposed algorithms successfully reduce the optimization complexity and solve the noise enhancement problem that exists in multiuser systems with non-orthogonal signatures. Numerical results show that significant improvement in power/spectral efficiency is achievable with reasonable computational complexity when the above schemes are applied.