Cooperative RF pattern matching positioning for LTE cellular systems

Abstract

In this paper, cooperative positioning for Long Term Evolution (LTE) cellular systems using Radio Frequency Pattern Matching (RFPM) is studied. Having the locations of users in a cellular system supports many applications such as location-based services and E911. Although Global Positioning System (GPS) can be found in every smartphone, its poor performance in indoor and dense environments encourages the development of cellular network-based solutions. Cellular localization has emerged in which the user locations can be determined by measurements obtained within the network without the aid of any external sources (e.g., GPS). Several positioning techniques have been considered in Release 9 of the 3rd Generation Partnership Project (3GPP) document such as Observed Time Difference Of Arrival (OTDOA) and Enhanced Cell ID (E-CID). In OTDOA, the User Equipment (UE) measures the time difference of signals from multiple eNodeBs and uses a trilateration algorithm to find its location. However, OTDOA performance can be highly degraded in rich multipath and non-line-of-sight environments particularly when there is strong interference. Hence, many companies and researchers are also evaluating other techniques such as RFPM in which the user location is estimated by comparing UE measurements with a series of reference data. RFPM is independent of line-of-sight conditions and has good performance in dense urban and indoor environments. In the current LTE networks, the UE can only communicate with eNodeBs. However, there are scenarios in which the UE is not able to communicate with a sufficient number of eNodeBs and cannot find its location without ambiguity. In this paper, a cooperative localization technique for LTE systems is proposed in which leveraging the Device-to-Device (D2D) communications protocol the UE communicates not only with eNodeBs but also with other UEs. It will be shown through computer simulations that the proposed positioning algorithm can significantly improve the positioning performance in LTE networks.