Spatial equalization of a radio-mobile channel without beamforming using the constant modulus algorithm (CMA)

The author considers the problem of signal recovery by a multisensor receiver in a multipath propagation channel. She shows that a spatial filtering can recover the transmitted signals under two conditions, namely that both the number of sensors and the number of paths be larger than the length of the intersymbol interference, which is assumed to be finite. Thereby, signal recovery is realized without beamforming, i.e. without forming a beam towards one of the paths while cancelling the others, which would require a number of sensors much larger than the number of paths. Spatial filtering is able to cancel a multipath jammer, provided that an additional number of sensors, equal to the ISI (intersymbol interference) length of the jammer, is available. The spatial filtering is obtained adaptively by a blind algorithm, the CMA, which relies on the property of the transmitted signal to have a constant modulus. Simulation results on the present spatial CMA were compared with results for a temporal single-sensor CMA. The latter failed to recover a correct signal constellation while spatial CMA succeeded, even in a noisy environment plus a jammer.<>