A Hybrid Lateration Time-Fingerprint Position Estimation Technique for Indoor UWB Systems E. Bogdani, D. Vouyioukas, N. Nomikos, D. N. Skoutas, C. Skianis Abstract—This paper presents a hybrid position estimation technique that is based on the integration of Fingerprinting (FP), Time-of-flight (ToF), and Trilateration approach. When empirical channel models are used with Ultra Wideband (UWB) systems, there are plenty of challenges that must be taken into consideration due to their dependence on frequency. Thus, when the position of a Blind Node (BLN) is estimated using the aforementioned techniques and the values deriving from these models, positioning error occurs. In order to minimize the positioning error, the proposed hybrid technique, called Lateration Time-FingerPrint (LTPF), is developed. The efficiency of the proposed positioning scheme is demonstrated through simulation results in terms of error probability and comparisons with other state-of-the-art positioning schemes. I. I NTRODUCTION Services and applications related to position estimation are based on emerging technologies and they are of great im- portance in our everyday life. The position information plays an important role in various applications that are related to industries, health systems, security and emergency services. In [1] a survey of indoor positioning systems in wireless personal networks is presented giving a comprehensive perspective of numerous Indoor Positioning Systems (IPSs), which include both commercial products and research-oriented solutions. Many integrated positioning systems have been developed in this research field, while different technologies, positioning techniques and propagation channels are used. UWB signals offer various advantages for communication and radar systems. Many studies that involve position detection use UWB signals’ capabilities, mainly focusing on locating the position of a target node that is referred as BLN in the network. The location estimation of the BLN, is conducted using various algorithms. In [2] UWB radios are used in order to locate a node in a wireless system, by applying different positioning techniques. In this work, different empirical path loss models, Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB and Positioning techniques are combined in order to specify the positioning error. A hybrid position estimation technique that combines Trilateration, ToF and FP techniques is proposed aiming to improve the estimation’s accuracy i.e. to minimize the localization error. Moreover, the type of UWB system, the positioning schemes and the path loss models that are used in the simulations are given in detail. Eleni Bogdani, Demosthenes Vouyioukas, Nikolaos Nomikos, Dimitrios N. Skoutas and Charalambos Skianis are with the Department of Informa- tion and Communication Systems Engineering, University of the Aegean, Karlovassi 83200, Samos, Greece (E-mails: icsdm14065@icsd.aegean.gr {dvouyiou,nnomikos,d.skoutas,cskianis}@aegean.gr). This paper is organized as follows. In Section II, the state-of-the-art on UWB positioning is presented. Section III describes in detail, the proposed hybrid Lateration Time- Fingerprint (LTFP) based positioning scheme. In Section IV, the system model is described, while Section V includes the numerical results in the area of probabilistic localization error. Finally, conclusions and future directions are given in Section VI. II. STATE- OF- THE-ART &SIMILAR WORKS Many studies in the literature propose localization schemes that are based on time, Received Signal Strength (RSS) and Angle of Arrival (AoA) of the received signals. RSS-based positioning techniques, such as FP, are used in [3], where an analytical model of a positioning system is presented. The main contribution is the probabilistic algorithm that returns the correct fingerprint for localization. In [4], an improved FP technique based on the UWB channel measurement is proposed, which makes use of updated versions of the FP databases. Results show that the accuracy is improved, thus minimizing the effect of the environment. Also in [5], the Trilateration technique is examined in relation with RSS and Time-of-Arrival (ToA) techniques. The results indicate that ToA outperforms RSS-based techniques in terms of positioning accuracy. The same conclusion is given in [2]. Moreover, a survey of the current indoor positioning techniques is presented in [6]. In this study, performance mea- surement criteria are discussed and several trade-offs among them are observed. Many works develop hybrid position estimation techniques aiming to enhance the performance of the criteria, as also described in [6]. In addition, time-based techniques are used in [7], where a modified Round Trip Time (RTT) ToA is used for mea- suring the distance between two UWB nodes. Results proved that localization accuracy is enhanced for all the considered deployments. Similar to this work, hybrid combinations of Channel Impulse Response (CIR)-based FP positioning and an iterative ToA real-time positioning method using UWB signaling is presented in [8] and [9]. It is shown that the proposed Levenberg-Marquardt-based iterative algorithm ef- fectively reduces the Non-Line-of-Sight (NLOS) errors, in both cases. Also, recently, many studies have been conducted in order to develop energy-efficient schemes for bandwidth allocation [10], or energy aware routing of traffic in cognitive radio networks [11]. It must be noted that such localization schemes