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OTFS-IDMA: An Unsourced Multiple Access Scheme for Doubly-Dispersive Channels

Davide Bergamasco, Federico Clazzer, Paolo Casari

TL;DR

This work addresses unsourced random access in high-mobility wireless links by combining OTFS modulation with sparse interleaver division multiple access in the delay-Doppler domain. The proposed two-stage receiver uses a compressive-sensing–based preamble detector to identify active users and estimate channels, followed by a single-user data decoder that leverages multipath diversity through max-ratio combining and SIC. Key contributions include a DD-domain full UMAC scheme, an AMP-based preamble detection method that accounts for DD shifts, and a data-decoding pipeline that integrates MRC, interleaver knowledge, and CRC-aided polar decoding. The results show that the approach can achieve competitive performance in doubly-dispersive channels and can exploit multipath diversity, with tradeoffs related to preamble collisions and design choices for phase separation.

Abstract

We present an unsourced multiple access (UMAC) scheme tailored to high-mobility wireless channels. The proposed construction is based on orthogonal time frequency space (OTFS) modulation and sparse interleaver division multiple access (IDMA) in the delay-Doppler (DD) domain. The receiver runs a compressive-sensing joint activity-detection and channel estimation process followed by a single-user decoder which harnesses multipath diversity via the maximal-ratio combining (MRC) principle. Numerical results show the potential of DD-based uncoordinated schemes in the presence of double selectivity, while remarking the design tradeoffs and remaining challenges introduced by the proposed design.

OTFS-IDMA: An Unsourced Multiple Access Scheme for Doubly-Dispersive Channels

TL;DR

This work addresses unsourced random access in high-mobility wireless links by combining OTFS modulation with sparse interleaver division multiple access in the delay-Doppler domain. The proposed two-stage receiver uses a compressive-sensing–based preamble detector to identify active users and estimate channels, followed by a single-user data decoder that leverages multipath diversity through max-ratio combining and SIC. Key contributions include a DD-domain full UMAC scheme, an AMP-based preamble detection method that accounts for DD shifts, and a data-decoding pipeline that integrates MRC, interleaver knowledge, and CRC-aided polar decoding. The results show that the approach can achieve competitive performance in doubly-dispersive channels and can exploit multipath diversity, with tradeoffs related to preamble collisions and design choices for phase separation.

Abstract

We present an unsourced multiple access (UMAC) scheme tailored to high-mobility wireless channels. The proposed construction is based on orthogonal time frequency space (OTFS) modulation and sparse interleaver division multiple access (IDMA) in the delay-Doppler (DD) domain. The receiver runs a compressive-sensing joint activity-detection and channel estimation process followed by a single-user decoder which harnesses multipath diversity via the maximal-ratio combining (MRC) principle. Numerical results show the potential of DD-based uncoordinated schemes in the presence of double selectivity, while remarking the design tradeoffs and remaining challenges introduced by the proposed design.
Paper Structure (8 sections, 8 equations, 5 figures)

This paper contains 8 sections, 8 equations, 5 figures.

Table of Contents

  1. Introduction
  2. System model
  3. Transmitter
  4. Receiver
  5. CS preamble decoder
  6. Data decoder
  7. Numerical results
  8. Conclusions

Figures (5)

  • Figure 1: Transmission scheme
  • Figure 2: Receiver scheme for data decoding.
  • Figure 3: Preamble miss detection probability versus the number of active users for different system and channel parameters.
  • Figure 4: Overall $E_b/N_0$ required to achieve $P_e = 0.05$ as a function of the number of active users assuming a single-path channel with unitary gain.
  • Figure 5: $E_b/N_0$ needed in the the second protocol phase to achieve $P_e = 0.05$ in the presence of fading as a function of the number of active users for a varying number of multipath components $P_k$.