Cooperative UTDOA Positioning in LTE Cellular Systems

This paper studies cooperative user positioning using uplink time-difference-of-arrival (UTDOA) measurements for 4G Long Term Evolution (LTE) cellular networks. Many applications in a cellular network, such as location-based services and E-911, rely on accurate locations of users in the network. Although the Global Positioning System (GPS) is widely used in cellphones, their poor localization performance in indoor and dense environments leads to the emergence of network-based localization techniques as a backup solution. In such techniques, the locations of users are determined via measurements obtained within the network without the aid of any external sources (e.g., GPS). UTDOA is a network-based localization technique introduced in Release 10 of the 3GPP LTE specification. In the UTDOA technique, the time difference of LTE uplink signals sent from the User Equipment (UE) to a set of several eNodeBs (base stations in LTE) are used as the means to estimate the UE's position. The location of the UE is then estimated through a trilateration algorithm. Currently, network-based localization techniques only rely on communications with eNodeBs. In this paper, a cooperative localization technique using UTDOA measurements is developed for LTE systems in which inter-UE communications are used to significantly improve the localizability and accuracy in the network. The performance of the proposed cooperative technique is evaluated through a series of computer simulations where the 3GPP simulation parameters are assumed.