Adaptive frequency-domain equalization and diversity combining for broadband wireless communications

We introduce a new kind of adaptive equalizer that operates in the spatial-frequency domain, and uses either least mean square (LMS) or recursive least squares (RLS) adaptive processing. We simulate the equalizer´s performance in an 8 Mb/s QPSK (quaternary phase shift keying) link over a frequency-selective, Rayleigh fading multipath channel with ~3 μs RMS delay spread, corresponding to 60 symbols of dispersion. Our results show rapid convergence and tracking for a range of mobile speeds (up to ~100 mph). Moreover, a 2-branch RLS equalizer requires only ~50 complex operations per detected bit, which, at 8 Mb/s, is close to achievable with state-of-the-art digital signal processing technology