On the equivalence of blind equalizers based on MRE and subspace intersections

Two classes of algorithms for multichannel blind equalization are the mutually referenced equalizer (MRE) method by Gesbert et al. (see ibid. vol.45, p.2307-17, 1997) and the subspace intersection (SSI) method by van der Veen et al. (see ibid., vol. 45, no.1, p.173-90, 1997). Although these methods seem, at first sight, unrelated, we show that certain variants of the SSI and the MRE methods both optimize a new blind criterion, which is referred to as maximum coherence and, thus, are equivalent.