To suppress the co-antenna interference in multiple input multiple output (MIMO) systems, an iterative receiver with a linear detector for complex symbols is investigated. We show that the considered generalized MIMO system, i.e., a system that transmits complex conjugate repetitions in addition to the pure data, requires the application of a widely linear (WL) detector. A WL detector consists of four real filters which are represented by two complex filters for the received signal and its complex conjugate, respectively. Furthermore, we present approximations of the detector that significantly reduce computational complexity with only little loss in frame-error rate performance. Simulation results show that the proposed MIMO system achieves large gains over standard solutions. Résumé Pour supprimer l’interférence entre les antennes d’un système à entrées et sorties multiples (MIMO), un récepteur itératif avec un détecteur linéaire pour des symboles complexes est examiné. Nous montrons que pour le système très général que nous considérons, c’est-a-dire un système qui transmet les informations elles-mêmes ainsi que des répétitions conjuguées, un détecteur linéaire au sens large (widely linear, WL) est exigé. Le détecteur WL comprend quatre filtres réels, représentés par 2 filtres complexes, un pour le signal reçu et un autre pour le conjugué du signal reçu. En plus, nous présentons des approximations du détecteur qui réduisent fortement la complexité avec seulement une petite perte en taux d’erreur de bloc. Des résultats de simulations montrent, que le système MIMO proposé a une meilleure performance que les solutions standards.

In this paper, Beam Pattern Scanning (BPS), a transmit diversity technique, is compared with two well known transmit diversity techniques, space-time block coding (STBC) and space-time trellis coding (STTC). In BPS (also called beam pattern oscillation), controlled time varying weight vectors are applied to the an-tenna array elements mounted at the base station (BS). This creates a small movement in the antenna array pattern directed toward the desired user. In rich scattering environments, this small beam pattern movement creates an artificial fast fading channel. The receiver is designed to exploit time diversity benefits of the fast fading channel. Via the application of simple combining techniques, BPS improves the probability-of-error performance and network capacity with minimal cost and complexity. In this work, to highlight the potential of the BPS, we compare BPS and Space-Time Coding (i.e., STBC and STTC) schemes. The comparisons are in terms of their complexity, system physical dimension, network capacity, probability-of-error performance, and spectrum efficiency. It is shown that BPS leads to higher network capacity and performance with a smaller antenna dimension and complexity with minimal loss in spectrum efficiency. This identifies BPS as a promising scheme for future wireless communications with smart antennas.