Literature presents many approaches for location detection of a mobile user using IEEE 802.11b wireless communication standard; generally localisation is limited to indoor scenarios, where GPS cannot be used, and is based on pattern matching algorithm. The paper aims to reach two different goals. The first is the proposal of the use of IEEE 802.11b standard for outdoor location detection; this choice is mainly justified by the large availability of communication cards at very low costs and by the limits of GPS, which may introduce not negligible errors in location detection. The second aim of the paper is the proposal of a new approach for outdoor wireless localisation, aimed to reduce the complexity featuring by the well-known localisation approaches based on pattern matching algorithm