IntroductionWe discuss techniques for signal separation and parameter estimation, using arrays of sensors, and applied to wireless communications. We start by deriving a signal processing model of the wireless channel. We then recall useful tools from linear algebra: QR, SVD, eigenvalue decompositions, projections. This gives us tools to discuss some more elementary receivers: the matched filter, the Wiener filter. Then we discuss important applications: estimation of angles and delays using ESPRIT, adaptive space-time filters, the constant modulus algorithm. Finally, we look at OFDM and CDMA systems and see how the above techniques can be applied to this.