NPRACH Receiver Equalizer for LTE-5G Compatibility

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Solution Overview

Problem

The challenge is to reconstruct NB-IoT PRACH signals without an NB-IoT-compatible LPHY, using only an LPHY capable of processing LTE or 5G-NR signals.

Innovation Solution

An additional processing module, functioning as an equalizer, is introduced between the LTE/5G-NR LPHY and the NB-IoT PRACH receiver. This equalizer processes the output from the LPHY to remove intercarrier interference (ICI) and recover the NB-IoT PRACH subcarriers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If an LPHY capable of processing only LTE or 5G-NR signals is used, then device complexity is reduced and versatility is improved, but the ability to process NB-IoT PRACH signals directly is lost

Engineering Contradiction:

ImproveversatilityVSAvoidNB-IoT PRACH signal processing capability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

An equalizer is introduced as an intermediary component between the LTE/5G-NR LPHY and the NB-IoT PRACH receiver. This equalizer processes the output from the LPHY to remove intercarrier interference (ICI) and recover the NB-IoT PRACH subcarriers, enabling compatibility without requiring a dedicated NB-IoT LPHY

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If different IFFT lengths are used at transmitter and receiver, then system flexibility is improved, but signal reconstruction accuracy deteriorates due to ICI

Engineering Contradiction:

Improvesystem flexibilityVSAvoidsignal reconstruction accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The equalizer serves as a mediator that compensates for the signal degradation caused by using different IFFT lengths. It processes the received signal to remove ICI introduced by the mismatched transform lengths, enabling accurate reconstruction despite the flexibility of using different lengths at transmitter and receiver

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system changes the parameter of transform length independently at transmitter and receiver sides. The transmitter uses one IFFT length while the receiver uses a different FFT length, and the equalizer compensates for this parameter mismatch to maintain signal integrity

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12273866B2Narrow-band internet of things physical random-access channel (NPRACH) receiver

Publication Date: 2025.04.08 MAVENIR US INC

AI summary

A method of Narrow-band Internet of Things physical random-access channel (NPRACH) communication includes: transmitting, from a user equipment (UE), a Narrow-band Internet of Things (NB-IoT) Orthogonal Frequency-Division Multiple Access (OFDMA) symbol using a transmit inverse fast Fourier transform (Tx-IFFT) having a first length; processing, at lower physical layer (LPHY) of a baseband unit (BBU), the NB-IoT OFDMA symbol using a receive fast Fourier transform (Rx-FFT) having a second length different from the first length to generate an Rx-FFT output; sending, from the LPHY of the BBU to upper physical layer (UPHY) of the BBU, a selected number of values of the Rx-FFT output corresponding to desired resources block in the NB-IoT OFDMA symbol; filtering, at the UPHY, intercarrier interference (ICI) from the selected number of values of the Rx-FFT output; and reconstructing, at the UPHY, the NB-IoT OFDMA symbol.