arxiv: 2605.10192 · v1 · submitted 2026-05-11 · 📡 eess.SP

Recognition: 2 theorem links

· Lean Theorem

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

Ali Gorcin, Hasan Atalay Gunel, Mohaned Chraiti

Pith reviewed 2026-05-12 03:15 UTC · model grok-4.3

classification 📡 eess.SP

keywords spatial phase manifold communicationsjoint communication and sensingLO-free receiverdirection of arrivalantenna correlationphase noiseIoT hardware

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The pith

SPMC encodes data and sensing information in inter-antenna phase differences recovered by an LO-free correlator receiver.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper introduces Spatial Phase Manifold Communications as a method for joint communication and sensing that operates without local oscillators. Information is carried in relative phases between antennas, which are extracted through antenna-domain correlations to recover both the transmitted data and direction-of-arrival signatures. This formulation turns the two tasks into inferences on the same unit-circle manifold, removing the need for LO distribution or separate channel estimation steps that dominate power use in conventional systems.

Core claim

SPMC exploits antenna-domain correlation to form a baseband observable that is a function of inter-antenna phase differences. 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. The framework comprises a manifold-domain signal model with phase-alphabet design, an LO-free quadrature spatial-correlator receiver that resolves phase-sign ambiguity without requiring an LO, and analysis of error probability and sensing precision including robustness to phase noise.

What carries the argument

The LO-free quadrature spatial-correlator receiver that forms baseband observables solely from antenna-domain correlations tied to inter-antenna phase differences and DoA.

Load-bearing premise

The LO-free quadrature spatial-correlator receiver can reliably resolve phase-sign ambiguity and form the required baseband observable solely from antenna-domain correlation without any local oscillator or explicit channel estimation.

What would settle it

A measurement campaign or simulation showing that the quadrature spatial correlator cannot resolve phase-sign ambiguity or yields error rates that do not match the predicted manifold-based analysis in the presence of realistic phase noise would falsify the receiver architecture.

Figures

Figures reproduced from arXiv: 2605.10192 by Ali Gorcin, Hasan Atalay Gunel, Mohaned Chraiti.

**Figure 1.** Figure 1: SPMC transmitter and receiver design. where ∆θ1m(t) ≜ αm(k) − α1(k) over the k-th symbol duration and nc,m(t) is an effective low-frequency noise term. Importantly, the phase noise ψ(t) cancels out as shown in (6). Hence, these observables can be formed without an LO. The cosine-only observable does not capture the sign ambiguity when mapping zc,m to ∆θ1m. To resolve this without an LO, a quadrature correl… view at source ↗

**Figure 2.** Figure 2: BER in the absence of phase noise. -5 0 5 10 15 20 25 SNR (dB) 10-6 10-5 10-4 10-3 10-2 10-1 100 BER SPMC BPSK SPMC 16-PSK Coherent BPSK ( =1° ) Coherent 16-PSK ( =1° ) Coherent BPSK ( =3° ) Coherent 16-PSK ( =3° ) Coherent BPSK ( =10° ) Coherent 16-PSK ( =10° ) [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗

**Figure 3.** Figure 3: BER performance as a function of SNR for different phase [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗

**Figure 4.** Figure 4: DoA estimation error distribution for varying values of [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗

**Figure 5.** Figure 5: DoA sensing accuracy under phase noise: RMSE of the [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗

read the original 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.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

SPMC embeds data and DoA in inter-antenna phase differences to skip the LO, but the quadrature correlator's sign resolution without any reference is the part that does not yet hold up.

read the letter

The key point is that this work tries to build joint communication and sensing around relative phases across antennas instead of a shared local oscillator. That moves the problem onto the unit circle manifold, where the same phase values carry both the symbols and the direction information. The receiver architecture is a quadrature spatial correlator meant to extract a signed baseband observable directly from antenna correlations, and the paper works out error rates plus sensing accuracy under phase noise. This targets the real cost of LO distribution in dense mmWave IoT nodes, and the framing avoids separate channel estimation steps, which is a practical simplification if it works.

Referee Report

2 major / 2 minor

Summary. The manuscript introduces Spatial Phase Manifold Communications (SPMC), a framework for joint communication and sensing (JCAS) that operates with a local-oscillator-free receiver. Information is encoded in inter-antenna phase differences, which are recovered via antenna-domain correlation to form baseband observables on the unit-circle manifold. This allows simultaneous data recovery and direction-of-arrival (DoA) sensing without traditional channel estimation. The paper presents a manifold-domain signal model, a phase-alphabet design, an LO-free quadrature spatial-correlator receiver that resolves phase-sign ambiguity, and analyses of error probability and sensing precision, including robustness to phase noise. The approach is positioned for low-power massive IoT applications at millimeter-wave frequencies.

Significance. If the central claims hold, this work could meaningfully advance low-power JCAS by removing the LO and explicit channel estimation requirements, which are major bottlenecks in massive IoT and mmWave deployments. The manifold-inference formulation that unifies data and DoA sensing is conceptually clean and offers a fresh decomposition of the JCAS problem. The provision of an error-probability analysis together with phase-noise robustness gives the proposal a quantitative foundation that many conceptual JCAS papers lack.

major comments (2)

[Receiver architecture and signal model] The resolution of phase-sign ambiguity is load-bearing for the entire baseband observable. The LO-free quadrature spatial-correlator is asserted to produce an odd function of the inter-antenna phase difference without any shared phase reference. Conventional correlators yield even functions (e.g., cos(ϕ)); the quadrature paths must therefore generate a sign-distinguishing statistic. The manuscript should supply the explicit derivation of this statistic (including the RF multiplication and baseband combination steps) and show that residual common-mode phase or path imbalance does not collapse the sign information back to an even function.
[Performance analysis] The error-probability and sensing-precision analysis implicitly assumes that the phase-sign resolution step succeeds with probability 1. If the sign statistic is noisy or biased under realistic RF impairments, both the communication BER and the DoA estimation variance will be affected. The paper should either derive the joint error expression that includes the sign-resolution failure probability or provide Monte-Carlo results that isolate this impairment.

minor comments (2)

[Signal model] The term 'phase-alphabet' is introduced without a compact mathematical definition or an example constellation diagram; adding one would clarify how symbols map to manifold points.
[Numerical results] Several figures would benefit from explicit axis labels indicating whether the plotted quantity is the raw correlator output or the post-processed manifold coordinate.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and insightful comments on our manuscript introducing SPMC for LO-free JCAS. The points raised highlight important aspects of the receiver architecture and performance analysis that merit clarification and expansion. We address each major comment below and indicate the revisions we will make.

read point-by-point responses

Referee: [Receiver architecture and signal model] The resolution of phase-sign ambiguity is load-bearing for the entire baseband observable. The LO-free quadrature spatial-correlator is asserted to produce an odd function of the inter-antenna phase difference without any shared phase reference. Conventional correlators yield even functions (e.g., cos(ϕ)); the quadrature paths must therefore generate a sign-distinguishing statistic. The manuscript should supply the explicit derivation of this statistic (including the RF multiplication and baseband combination steps) and show that residual common-mode phase or path imbalance does not collapse the sign information back to an even function.

Authors: We agree that the explicit derivation of the sign-resolving statistic is necessary to substantiate the central claim of the LO-free quadrature spatial-correlator. While Section III-B of the manuscript describes the architecture and states that it produces an odd function of the inter-antenna phase, the step-by-step derivation from the RF signal model through quadrature multiplications and baseband combining was not fully expanded. In the revised manuscript we will insert a complete derivation, including the mathematical expressions for the RF multiplication and baseband combination steps. We will also add an analysis showing that residual common-mode phase and path imbalance preserve the odd-function property and do not collapse the sign information to an even function. This material will be placed in a new subsection or appendix for clarity. revision: yes
Referee: [Performance analysis] The error-probability and sensing-precision analysis implicitly assumes that the phase-sign resolution step succeeds with probability 1. If the sign statistic is noisy or biased under realistic RF impairments, both the communication BER and the DoA estimation variance will be affected. The paper should either derive the joint error expression that includes the sign-resolution failure probability or provide Monte-Carlo results that isolate this impairment.

Authors: The referee is correct that the closed-form error-probability and sensing-precision expressions in Section IV are derived under the assumption of perfect sign resolution. This simplification was adopted to obtain tractable analytic results, but it leaves open the question of robustness to noisy sign statistics. We will revise the manuscript to include Monte-Carlo simulation results that isolate the effect of imperfect sign resolution under realistic RF impairments (phase noise, path imbalance, and additive noise). These simulations will report the resulting degradation in both communication BER and DoA estimation variance. If space allows, we will also outline the joint error expression that incorporates the sign-resolution failure probability. The new results will be presented in an updated Section IV or a dedicated subsection. revision: yes

Circularity Check

0 steps flagged

No significant circularity in SPMC derivation

full rationale

The paper defines a new signal model based on antenna-domain correlation producing a baseband observable from inter-antenna phase differences, then introduces an LO-free quadrature spatial-correlator architecture to resolve phase-sign ambiguity and recasts JCAS as inference on the unit-circle manifold. These elements are presented as original constructions rather than reductions of prior fitted parameters or self-citations. Error-probability and sensing-precision analyses are derived from the proposed model without evidence of self-definitional loops or load-bearing self-citations that force the central claims. The derivation chain remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 3 invented entities

Review based on abstract only; several new concepts are introduced whose supporting assumptions and parameters are not detailed.

axioms (2)

domain assumption Antenna-domain correlation produces a baseband observable that depends only on inter-antenna phase differences and is independent of local oscillator phase.
This is the central premise enabling LO-free operation.
domain assumption Phase differences between antennas are deterministically tied to direction-of-arrival.
Invoked to link communication and sensing through the same manifold.

invented entities (3)

Spatial Phase Manifold Communications (SPMC) no independent evidence
purpose: New paradigm for embedding and recovering data via spatial phase on the unit circle.
Introduced as the core contribution of the paper.
phase-alphabet no independent evidence
purpose: Discrete set of phases used to encode information.
Part of the manifold-domain signal model.
LO-free quadrature spatial-correlator no independent evidence
purpose: Receiver architecture that resolves phase-sign ambiguity without an LO.
New hardware concept described in the framework.

pith-pipeline@v0.9.0 · 5540 in / 1557 out tokens · 60469 ms · 2026-05-12T03:15:39.078294+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear
Von Mises likelihood p(q|Δθ) ∝ exp(κ Re{q e^{-j(m-1)Δθ}})

Reference graph

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