SNR maximization and modulo loss reduction for Tomlinson-Harashima precoding

Compared to linear precoding, Tomlinson-Harashima precoding (THP) requires less transmit power to eliminate the spatial interference in a multi-user downlink scenario involving a multi-antenna transmitter and geographically separated receivers. However, THP gives rise to certain performance losses, referred to as modulo loss and power loss. Based on the observation that part of the users can omit the modulo operation at the receiver during an entire frame, we present an alternative detector, which reduces the modulo loss compared to the conventional detector. In addition, this contribution compares several existing and novel algorithms for selecting the user ordering and the rotation of the constellations at the transmitter, to increase the SNR at the detector and decrease the modulo loss for the alternative detector. Compared to the better of linear precoding and THP with conventional detector, the optimized alternative detector achieves significant gains (up to about 4 dB) for terrestrial wireless communication, whereas smaller gains (up to about 1 dB) are obtained for multi-beam satellite communication

Multi-user interference mitigation techniques for broadband multi-beam satellite systems

This paper presents a comprehensive evaluation of multi-user interference mitigation techniques for a broadband multi-beam satellite system. More in detail, present multi-beam satellite systems are strongly limited by the effect of inter-beam interference, which has to be necessarily reduced with the adoption of advanced signal processing techniques. The limitation in the bandwidth of the feeder link further exacerbates this problem, forcing gateways to operate only on a fraction of the total beams number, thus limiting the effectiveness of multi-user interference mitigation techniques unless some form of gateway collaboration is not adopted. This paper discusses the possible performance gain achievable by gateway cooperation, as opposed to centralized operations, and results are presented for the return link, based on both analytical considerations and numerical simulations on a realistic scenario

Optimisation de la gestion des ressources voie retour

L'optimisation de l'utilisation des liens satellites est un enjeu majeur pour augmenter la rentabilité des systèmes satellites. L'augmentation de la réutilisation des fréquences est une des approches les plus prometteuses. La réutilisation des fréquences permet de transmettre plus d'informations sur une même fréquence, pour peu que les interférences entre les deux signaux ne soient pas trop importantes. Il est donc capital de contrôler l'impact de ces interférences, que ce soit via l'utilisation de schémas de réutilisation de fréquences, ou encore via des techniques de coordination dynamique des interférences, où la sélection des utilisateurs qui peuvent transmettre sur les mêmes fréquences est faite en prenant les interférences en compt