Multi-user round-trip delay ranging scheme with sparsely allocated OFDM signals

Ranging performance is a fundamental and crucial figure of merit for any position estimation technique. Cooperative positioning requires accurate range estimation with low latency. Common solutions employ time slots to sequentially range among all possible mobile nodes. In this case the number of ranging links increases quadratically with the number of users which increases latency significantly. We propose a subcarrier-interleaved round-trip delay ranging scheme with amplify and forward relaying to overcome this drawback. We show that we can reach linear complexity and significantly reduce latency. The obtained low latency allows higher flexibility and higher scalability compared to existing solutions. Furthermore, we study theoretical performances with derived Cramér-Rao lower-bounds for signals with orthogonal frequency division multiplex. Simulation results with 3GPP-LTE system parameters and our proposed sparse allocation show that our approach is well suited for low-latency and highly accurate range estimation.