Timestamp Estimation in P802.15.4z Amendment

Abstract

Due to the known issue that the ranging in the 802.15.4™-2015 standard is prone to external attacks, the enhanced impulse radio (EiR), a new amendment still under development, advances the secure ranging protocol by encryption of physical layer (PHY) timestamp sequence using the AES-128 encryption algorithm. This new amendment brings many changes and enhancements which affect the impulse-radio ultra-wideband (IR-UWB) ranging procedures. The timestamp detection is the base factor in the accuracy of range estimation and inherently in the localization precision. This paper analyses the key parts of PHY which have a great contribution in timestamp estimation precision, particularly: UWB pulse, channel sounding and timestamp estimation using ciphered sequence and frequency selective fading. Unlike EiR, where the UWB pulse is defined in the time domain, in this article, the UWB pulse is synthesized from the power spectral density mask, and it is shown that the use of the entire allocated spectrum results in a decrease in risetime, an increase in pulse amplitude, and an attenuation of lateral lobes. The paper proposes a random spreading of the scrambled timestamp sequence (STS), resulting in an improvement in timestamp estimation by the attenuation lateral lobes of the correlation. The timestamp estimation in the noisy channels with non-line-of-sight and multipath propagation is achieved by cross-correlation of the received STS with the locally generated replica of STS. The propagation in the UWB channel with frequency selective fading results in small errors in the timestamp detection.

Experimental Evaluation of IEEE 802.15.4z UWB Ranging Performance under Interference

“…While the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4a-2015 standard [20] suffers from not providing methods to counter these synchronization issues, the newly introduced IEEE 802.15.4z-2020 standard [21] provides measures to reduce these effects. Next to many improvements in the allowable Physical Layer (PHY) configuration [22,23] and reduced ranging times [24], another cryptographic spreading sequence, Scrambled Time Sequence (STS) is introduced to detect and mitigate erroneous TOA estimation [25][26][27].…”

Antennas and Propagation: A Sensor Approach

“…The work in [ 5 ] proposes a random spreading of the scrambled timestamp sequence (STS) in ultra-wide-band (UWB) pulse communications. The timestamp estimation is improved by reducing the side lobes of the correlation.…”