Random Access Preamble Detection for OTFS

Random-access preamble detection (RAPD) is considered to enable the contention-based random-access procedure for rectangularly-pulsed orthogonal time frequency space (OTFS) systems operating on linear time-varying multipath (LTV) channels in uplink high-mobility multiple-access environments. Particularly, a new preamble signaling format is designed by adopting the reduced-cyclic-prefix OTFS waveform format, cyclically shiftable zero-autocorrelation (ZAC) sequences, and multiple scalable preamble frame intervals to represent requestable access channels and enable reliable RAPD over LTV channels. A ZAC-sequence-measure (ZACSM) -based RAPD approach is also developed to identify multiple requesting preamble signals at the base station receiver. The ZACSM-based RAPD system is analytically studied in terms of false alarm, outage, and false identification probabilities for asynchronous reception of multiple requesting signals over deterministic LTV channels. When operating over random LTV channels exhibiting fractional delay and Doppler shifts, the ZACSM-based RAPD system can provide higher reliability than conventional RAPD systems in the sense of achieving the smaller average false identification probability while constraining upper bounds to false alarm probability and average outage probability. Meanwhile, the ZACSM-based RAPD system can provide a scalable capacity of requestable access channels by allocating nearly the same spectral-temporal resource for preamble signaling.