Minimax Design of Constant Modulus MIMO Waveforms

Waveform optimization is a crucial step in the design of a multiple-input multiple-output (MIMO) system. This paper considers the joint optimization of constant modulus waveforms and mismatched (or matched) receive filters to suppress the auto- and cross-correlations using the minimax (ell-{infty}) design criterion. For practical waveform length and system size, the waveform design problem becomes quite challenging due to the large problem size (more than 10 {5} unimodular complex variables and 10 {6} nonlinear constraints). In addition to the large size, this problem is nonconvex, nonsmooth, and as such, can not be handled effectively by the existing waveform design algorithms or off-the-shelve optimization tools. This paper develops an efficient primal-dual type algorithm with low per-iteration complexity to solve this problem. Numerical comparison shows that the waveforms based on the minimax design outperform those obtained from the existing ell-{2} norm design by 4-5 dBs in terms of peak sidelobe levels (PSL).