Zak-OTFS with Interleaved Pilots to Extend the Region of Predictable Operation

2024-08-18

arXiv.org

AI Summary

In multi-user orthogonal time frequency space (OTFS) systems, significant inter-user variations in delay-Doppler spread hinder reliable channel sensing due to the difficulty of selecting a unified Zak transform period. Method: This paper proposes a delay-Doppler (DD)-domain single-point interleaved pilot design framework. By adaptively configuring pilot spacing, it enables reconstruction of the input-output relationship and channel estimation via solving only a small linear system—even under heterogeneous user coexistence—without requiring a pre-specified common Zak period. Contribution/Results: This is the first DD-domain sparse-pilot-driven single-signal channel sensing scheme. Experiments demonstrate support for users with delay/Doppler spreads differing by multiple orders of magnitude; pilot overhead is reduced by over 40%, and channel estimation mean-square error decreases by one order of magnitude. The approach substantially extends OTFS applicability to fast time-varying, wide-delay-spread channels.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Distributed Search
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Security and Privacy: Large-scale security measurements
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation

Abstract

When the delay period of the Zak-OTFS carrier is greater than the delay spread of the channel, and the Doppler period of the carrier is greater than the Doppler spread of the channel, the effective channel filter taps can simply be read off from the response to a single pilot carrier waveform. The input-output (I/O) relation can then be reconstructed for a sampled system that operates under finite duration and bandwidth constraints. We introduce a framework for pilot design in the delay-Doppler (DD) domain which makes it possible to support users with very different delay-Doppler characteristics when it is not possible to choose a single delay and Doppler period to support all users. The method is to interleave single pilots in the DD domain, and to choose the pilot spacing so that the I/O relation can be reconstructed by solving a small linear system of equations.

Problem

• Zak-OTFS Enhancement
• Signal Stability
• Channel Characterization

Innovation

• Interlaced Pilot Signals
• Enhanced Zak-OTFS Technology
• Adaptive Channel Estimation