C-V2X Preamble Interference Cancellation via Channel Estimation

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Solution Overview

Problem

Vehicular communication systems face interference issues when different protocols, such as IEEE 802.11p and C-V2X, operate in the same frequency channel, leading to packet collisions and decoding challenges due to rich multipath channels and large delay spreads.

Innovation Solution

Incorporating a preamble with IEEE 802.11p elements into C-V2X packets to reserve channel time, and employing signal processing techniques like blanking IQ samples and channel estimation to mitigate inter-symbol interference and improve decoding accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If preambles of IEEE 802.11p are incorporated into C-V2X packets to reserve channel time, then co-channel coexistence is improved, but inter-symbol interference increases when multiple vehicles transmit simultaneously

Engineering Contradiction:

Improveco-channel coexistenceVSAvoidinter-symbol interference

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful inter-symbol interference caused by simultaneous preamble transmissions into a beneficial mechanism by having receivers blank out (zero out) the interfering portions of the signal. This allows the receiver to identify and exclude the interference from decoding, thereby maintaining reliable communication while enabling multiple vehicles to use the same channel simultaneously.

Inventive Principle:

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

Solution Approach 2:

The patent introduces an intermediary signal processing technique where the receiver actively manages the interference by blanking out specific portions of the received signal. This intermediary processing step allows the system to handle the harmful interference from simultaneous transmissions without requiring physical separation or temporal scheduling, thus enabling co-channel coexistence.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If multiple vehicles transmit simultaneously in the same geographical region, then communication productivity increases, but packet collision probability increases

Engineering Contradiction:

Improvecommunication productivityVSAvoidpacket collision probability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent transforms the harmful effect of simultaneous transmissions (which cause packet collisions) into a beneficial feature by using the interference pattern itself as a signal. The receiver uses channel estimation and blanking techniques to identify and extract the intended message from the interfering signal, allowing multiple vehicles to transmit simultaneously without collisions.

Inventive Principle:

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

Solution Approach 2:

The patent employs feedback mechanisms where the receiver continuously monitors the channel conditions and adjusts its processing accordingly. By estimating the channel characteristics and using this feedback information to guide the blanking and decoding processes, the system maintains reliable communication even under high productivity conditions with multiple simultaneous transmissions.

Inventive Principle:

Principle #23Feedback

3Reliability

If rich multipath channels and large delay spread are present, then signal transmission reliability is improved through diversity, but decoding accuracy deteriorates

Engineering Contradiction:

Improvesignal transmission reliabilityVSAvoiddecoding accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent converts the harmful effect of multipath interference and delay spread on decoding accuracy into a benefit by using these channel characteristics to improve signal discrimination. The receiver uses channel estimation to characterize the multipath effects and applies blanking techniques that leverage the delay spread information to identify and exclude interfering components, thereby maintaining both reliability and decoding accuracy.

Inventive Principle:

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

Data Source

PatentUS20230421413A1Vehicular communication protocols with co-channel coexistence and inter-symbol interferance calculation

Publication Date: 2023.12.28 BV NXP BV

AI summary

RF signal is received (1006). The received RF signal includes a first RF signal encoding a first orthogonal frequency-division multiplexing (OFDM) symbol of a first long-term evolution (LTE) V2X data packet. A channel estimation in the time domain is determined (1012) using the received signal and an as-transmitted time domain version of an L-LTF symbol is determined (1014). The channel estimation in the time domain is applied to the as-transmitted time domain version of the L-LTF symbol to determine an as-transmitted version of the L-LTF symbol that exhibits channel fading (1018). A first portion of the as-transmitted version of the L-LTF symbol that exhibits channel fading is subtracted from a second portion of the received RF signal (1022) to remove inter-symbol interference from the received signal to generate a second received RF signal.