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Geolocation aware services are becoming attractive with the deployment of next generation wireless networks and broadband multimedia wireless networks (i.e. ubiquitous and pervasive computing) especially in indoor and campus areas. In order to construct an ad-hoc network the upcoming ultra-wideband (UWB) radio technology holds great promise for revolutionizing wireless communications especially in indoor environments (office, residential, industrial). The two proposals considered in this paper are: a multi band OFDM approach, based on the transmission of non-impulse OFDM signals combined with frequency hopping (FH), and the direct-sequence (DS) UWB approach, based on impulse radio transmission of UWB DS-coded pulses. In this paper, the problem of ranging error estimation in obstructed line-of-sight (OLOS) multipath channels is investigated. A time-of-arrival (ToA) based ranging scheme using UWB radio link is proposed. Results show that the accuracy enhancement depends on two principal factors: the strength of multipath components and the variance of non-line-of-sight (NLOS) delays, which it shows that DS-UWB is best suited for ranging, due to its larger bandwidth and its higher frequencies of operation.