In this paper, the beamforming design and power allocation problem for MIMO-OFDM cognitive radio broadcast channel is investigated. Due to the non-convexity of this problem, the Block Diagonalization is proposed as beamforming strategy which converts the problem to only a power allocation problem. The power allocation problem is solved based on the standard convex optimization framework, and iterative algorithms with a closed form power allocation are proposed to search optimal dual variables based on KKT conditions. As a comparison, suboptimal solutions with lower complexity are proposed based on resolving combinatorial constraints to individual constraints. Simulation results validate proposed algorithms and evaluate their performance over various scenarios.
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