Cognitive Suppression of Multipath Interference in Angular Domain

This paper deals with a cognitive approach used to reduce the interference generated by/toward another system operating on the same frequency band. A typical scenario is represented by an Underlay Cognitive Networks where a secondary system makes use of the same frequency band of the primary system but should transmit without affecting the primary system reception. However, this situation can arise also when an intentional jammer tries to destroy the primary system communications. In this paper the interference is detected by using a spatial sensing approach instead of the classical spectrum sensing: multiple-antenna technology is considered to exploit the angle dimension as a new spectrum opportunity. In particular Multiple Signal Classification (MuSiC) algorithm is used to detect the Direction of Arrival (DoA) of the interference source. We assume actual propagation environments, with multipath components characterized by large angle spread, and actual antenna size with a limited number of elements. This leads to scenarios in which the number of resolvable directions is higher than the number of antennas that typically limits the DoA estimation capabilities. DoA information is then used in transmission inserting nulls in the estimated directions thus protecting the useful information. The proposed scheme permits to increase the signal to interference ratio at the receiver side thus reducing the achieved error rate.