Implementation and performance evaluation of cellular NB-IoT OTDOA positioning

This contribution describes the first implementation of an integrated modem supporting NB-IoT OTDOA positioning. The integration of a dedicated hardware accelerator provides the necessary processing power for time-domain cross-correlations of OFDM signals and enables successful position fixes at highly negative SINR. The presented HW/SW partitioning scheme allows to minimize the HW overhead, keeping it below 2% of the System on Chip (SoC)'s area, while allowing for flexible algorithms taking advantage of the integrated processor system. Measurements with fabricated silicon in a laboratory environment prove that 3GPP accuracy requirements are easily met. The achieved Root Mean Square (RMS) positioning accuracy of 48.5 m and 65.5 m in normal and extended coverage, respectively, shows the potential of NB-IoT positioning as a complement to GNSS. Potential use cases are indoor applications and the improvement of cyber-physical systems' security by adding redundancy to their positioning capabilities.