Zero-forcing precoding for frequency selective MIMO channels with H∞H∞ criterion and causality constraint

We consider zero-forcing equalization of frequency selective multiple-input multiple-output (MIMO) channels by causal and linear time-invariant precoders in the presence of intersymbol interference. Our motivation is twofold. First, we are concerned with the optimal performance of causal precoders from a worst case point of view. Therefore we construct an optimal causal precoder, where contrary to other works our construction is not limited to finite or rational impulse responses. Moreover, we derive a novel numerical approach to computation of the optimal performance index achievable by causal precoders. This quantity is important in the numerical determination of optimal precoders.