Efficient Bit Flipping-Based Digital Side Lobe Mitigation for Secure UWB Ranging

The IEEE 802.15.4z standard enabled secure ranging based on introducing a ciphered sequence called Scrambled Time Sequence (STS) in the Ultra-Wideband (UWB) packet. The channel impulse response (CIR) estimated by the STS sequence of the UWB packet has some side lobes due to STS sequence pseudo-random structure. The side lobes of a strong Non-Line-of-Sight (NLoS) in the CIR may obscure/distort the weak Line-of-Sight, leading to degradation of the ranging performance. In this paper, we propose an algorithm based on a structured bit flipping, referred to as bit flipping-based digital side lobe mitigation (BP-DSM), that reduces the magnitude of the side lobes in the estimated CIR of STS. BP-DSM improves the precision of the range estimation using the CIR of STS by up to 10 times. Additionally, BP-DSM is fully feedforward, avoiding the need for the time-consuming and computationally expensive re-computation of side lobes for each bit flipping trial, as required by an exhaustive search scheme. Consequently, BP-DSM is well-suited for secure UWB range estimation with limited processing time and power consumption.