First Responder Indoor Location Using LTE Direct Mode Operations

University of Cincinnati

Without GPS, indoor location is a difficult problem, especially for emergency first responders since a pre-installed WiFi or beacon transmitter infrastructure may no longer be available in an emergency situation. On the other hand, emergency first responders must carry radios for critical communication needs in emergency response missions. With the advent of Release 12 of the 3GPP specifications, LTE devices now have the capability to support Device-to-Device communications enabling direct mode operations and Proximity Services (ProSe) that allows the devices to detect each other and communicate directly with one another without the aid of a cellular network infrastructure. In this work, we use the LTE ProSe mode and the system information blocks of the LTE sidelink communication signals to measure time of arrivals among a few such communication devices that form an ad hoc wireless network, thereby providing indoor location service that uses no additional hardware device and uses almost no communications payload bandwidth. - July 2019

Meet the Team

Principle Investigator: Howard Fan - University of Cincinnati
Julian Wang - University of Cincinnati

Project Overview

It is well known that GPS signals are very weak so they cannot be received indoors.  Without GPS, indoor location is a difficult problem, especially for emergency first responders since a pre-installed WiFi or beacon transmitter infrastructure may no longer be available in an emergency situation.  Over the  course of this project, the team will work to prove the feasibility of the concept of an ad hoc wireless-network-based location service by implementing it on a software defined radio (SDR) network using generic SDRs and testing it in a real world indoor setting.

With the advent of Release 12 of the 3GPP specifications, LTE devices have the capability to support Device-to-Device (D2D) communications enabling Proximity Services (ProSe) that allows the devices to detect each other and communicate directly with one another (direct mode operations or DMO), without the aid of the cellular network infrastructure. This new ProSe voice service is ideally suited for the team’s method to also provide location services using the same set of hardware devices.

One significant challenge is multipath propagation in an indoor environment. The proposed R&D effort will be spent on multipath mitigation methods and implementation. A network communications protocol also needs to be designed to accommodate not only the proposed location service, but also the mission critical voice service on LTE devices using the ProSe D2D standard. In addition, the increasingly popular standardized building information modeling (BIM) will also be utilized by pulling needed information from it, such as building interior layout, window, door, fire extinguisher and other critical element locations. Finally, the proposed method will be implemented on SDRs, which will transmit over-the-air and be tested inside an actual building, verifying that the network can actually perform localization of all participating nodes without GPS. The expected accuracy will be at meter level, and locations of all nodes will be displayed on a laptop overlaying a building interior layout.

If successful, this will enable location based services on a mission critical voice communications network, without adding another set of devices. This will help to save cost and reduce size, weight, and power of devices that a first responder must carry. This location capability will significantly enhance the mission critical voice communications.  With potential success of the proposed final test, the technology will be ready to be ported into actual LTE D2D software defined radios as a final product. A technology transfer partner has been identified who is able to help commercializing this new technology into an actual product.