Single-Carrier Receiver Phase Recovery for NLOS Wireless Backhaul

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Solution Overview

Problem

Current wireless backhaul systems face challenges in non-line-of-sight scenarios due to reflections and diffractions, which lead to phase noise, increasing costs and power consumption, especially in high modulation order applications like 6 GHz to 86 GHz links.

Innovation Solution

A single carrier receiver with a decision-feedback equalizer and an auxiliary branch for phase noise recovery is implemented, reducing equalizer length and mitigating loop-delay issues, thereby addressing phase noise and reflections/diffractions in wireless backhaul systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional wireless backhaul systems operate in non-line-of-sight scenarios, then coverage is improved, but phase noise increases leading to high cost and power consumption

Engineering Contradiction:

Improvecoverage in non-line-of-sight scenariosVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The receiver is segmented into multiple functional blocks: equalizer, phase noise estimator, and carrier recovery unit. Each block processes signals independently to handle specific aspects of the channel impairment, allowing efficient power usage while maintaining coverage in non-line-of-sight scenarios

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A feedback mechanism is implemented where the phase noise estimator continuously monitors and estimates phase noise from the received signal, and this estimation is fed back to the carrier recovery unit to adjust and compensate for phase noise in real-time, reducing power consumption while maintaining coverage

Inventive Principle:

Principle #23Feedback

2Reliability

If equalizer length is increased to handle reflections and diffractions, then reliability is improved, but device complexity and power consumption increase

Engineering Contradiction:

Improvetolerance to reflections and diffractionsVSAvoidequalizer length

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The decision-feedback equalizer uses feedback from detected symbols to adjust equalizer coefficients, achieving high reliability in handling reflections and diffractions with a shorter equalizer length compared to traditional forward-only equalizers

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The equalizer adapts its parameters (coefficients) dynamically based on channel conditions through training and detection phases, allowing it to maintain high reliability with optimized length by changing its operational parameters rather than relying on fixed long coefficients

Inventive Principle:

Principle #35Parameter changes

3Productivity

If high modulation order is used to improve spectral efficiency, then data rate is improved, but tolerance to phase noise decreases

Engineering Contradiction:

Improvespectral efficiencyVSAvoidtolerance to phase noise

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The phase noise estimation and compensation feedback loop enables the system to use high modulation orders by continuously correcting phase noise effects, thereby maintaining both high spectral efficiency and tolerance to phase noise through active compensation

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system converts the harmful effect of phase noise into a measurable parameter that can be estimated and compensated, allowing high modulation orders to be used effectively by transforming phase noise from a limiting factor into a correctable distortion

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Productivity

If phase noise compensation is implemented to enable high modulation order, then spectral efficiency is improved, but cost and power consumption increase

Engineering Contradiction:

Improvespectral efficiencyVSAvoidcost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The receiver performs self-service phase noise compensation by estimating phase noise from the received signal itself and using this estimation to correct the signal, eliminating the need for expensive external phase noise correction hardware while maintaining high spectral efficiency

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS10491431B2Wireless backhaul

Publication Date: 2019.11.26 MAXLINEAR ASIA SINGAPORE PTE LTD

AI summary

In the subject system, a receiver includes a feed forward circuit, a phase recovery circuit, and a feedback circuit. The feed forward circuit compensates for near reflections and provides an input to the phase recovery circuit and the feedback circuit. The phase recovery circuit performs phase recovery and provides phase recovery information to the feedback circuit. The feedback circuit adjusts and/or corrects a received symbol based at least in part on the received phase recovery information.