Synchronous and fractionally-spaced blind equalization in dually-polarized digital radio links

Two-dimensional equalization structures with symbol-rate or fractional tap-spacing are used to counteract the combined effects of selective fading and cross-polarization interference in dually polarized digital radio links. After generalizing the known optimum equalizers to the case of two-dimensional complex signals, steady-state analysis is presented based on the evaluation of a bound on the outage probability. Finite-length structures are considered and compared to the optimum linear receiver. The blind acquisition of two-dimensional T- and T/2-spaced equalizers is also shown by using a stop-and-go decision-directed algorithm in a simulation analysis