LO-Free Receiver: Next-Gen Low-Power Joint Communication and Sensing

TL;DR

This paper proposes a novel LO-free receiver paradigm using spatial phase differences for joint communication and sensing, reducing hardware complexity and power consumption, especially suitable for massive IoT deployments.

Contribution

It introduces SPMC, a new framework that encodes data and sensing information via inter-antenna phase differences without LOs, along with a receiver architecture and analysis.

Findings

LO-free quadrature correlator effectively resolves phase ambiguity

Framework supports robust joint communication and sensing

Suitable for low-power, high-frequency IoT applications

Abstract

This paper introduces and analyzes Spatial Phase Manifold Communications (SPMC), a paradigm that facilitates joint communication and sensing (JCAS) over Local Oscillator (LO) free receiver. Information is embedded in, and recovered from, the relative spatial phase between antennas. In contrast to conventional coherent receivers that rely on LOs and on channel estimation/equalization, SPMC exploits antenna-domain correlation to form a baseband observable that is a function of inter-antenna phase differences. Since these phase differences are fundamentally tied to Direction-of-Arrival (DoA) and vice-versa, the formulation recasts communication and sensing as inference over the unit-circle manifold and thus naturally supports JCAS decomposition, i.e., data and spatial sensing are encoded and recovered through DoA signatures. We develop a comprehensive framework comprising: (i) a manifold-domain signal model and corresponding phase-alphabet design; (ii) an LO-free quadrature spatial-correlator receiver architecture that resolves the phase-sign ambiguity without requiring an LO; and (iii) an analysis of error probability and sensing precision, including robustness to phase noise. The proposed paradigm is particularly suited to massive Internet-of-Things (IoT) deployments, for which hardware simplicity, LO distribution cost, power consumption, and seamless sensing integration are critical, especially at millimeter-wave and higher carrier frequencies.