Improved multi-channel ranging precision bound for narrowband LPWAN in multipath scenarios

Accurate range estimation with narrowband low power radio devices is challenging due to limited signal bandwidth and high frequency offsets of low-cost oscillators. The present paper provides new results concerning the Cramer Rao bounds of narrowband ranging systems applying a multi-channel coherent processing approach. Particularly, compared to existing literature, oscillator frequency offsets and multipath influence are taken into account. By numerical simulation it is shown, how the radio channel frequency selectivity degrades the ranging precision. Finally, a few guidelines for the design of new long range low-cost ranging systems are provided.