OFDM Transmitter Segmentation for Robust Signal Detection

Solution Overview

Problem

In Orthogonal Frequency Division Multiplexing (OFDM) systems, increasing the number of sub-carriers for improved spectral efficiency can lead to reduced robustness in data recovery, especially in challenging radio environments, due to increased Doppler frequency shifts and multipath propagation, requiring higher signal-to-noise ratios for reliable bit error rates.

Innovation Solution

A transmitter is designed to include a signature sequence combined with the first OFDM symbol carrying signalling data, allowing for improved detection in challenging environments, and a reduced number of pilot sub-carriers for estimating a coarse frequency offset, while the second OFDM symbols carry payload data with a higher number of sub-carriers for spectral efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the number of sub-carriers is increased to improve spectral efficiency, then spectral efficiency is improved, but robustness in data recovery deteriorates due to increased Doppler frequency shifts and multipath propagation

Engineering Contradiction:

Improvespectral efficiencyVSAvoidrobustness in data recovery

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The transmission is divided into two distinct OFDM symbols: a first OFDM symbol with a reduced number of sub-carriers optimized for robustness in challenging radio environments, and a second OFDM symbol with a higher number of sub-carriers optimized for spectral efficiency. This segmentation allows each symbol to serve its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the transmission frame have different qualities optimized for their specific purposes. The first OFDM symbol uses local quality parameters (fewer sub-carriers, higher guard interval) suited for reliable detection in harsh environments, while the second OFDM symbol uses parameters (more sub-carriers, lower guard interval) suited for high spectral efficiency.

Inventive Principle:

Principle #3Local quality

2Productivity

If the number of sub-carriers is increased to improve spectral efficiency, then spectral efficiency is improved, but the signal-to-noise ratio requirement increases for achieving target bit error rate

Engineering Contradiction:

Improvespectral efficiencyVSAvoidsignal-to-noise ratio requirement

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The transmission is divided into two distinct OFDM symbols: a first OFDM symbol with a reduced number of sub-carriers optimized for robustness in challenging radio environments, and a second OFDM symbol with a higher number of sub-carriers optimized for spectral efficiency. This segmentation allows each symbol to serve its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first OFDM symbol acts as a preliminary action that establishes reliable detection and synchronization before the second OFDM symbol carries the main payload data. By first ensuring robust detection with fewer sub-carriers, the system prepares the receiver for the subsequent high-efficiency transmission.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If the guard interval is minimized to increase spectral efficiency, then spectral efficiency is improved, but the ability to cope with multipath propagation deteriorates

Engineering Contradiction:

Improvespectral efficiencyVSAvoidmultipath propagation

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The transmission is divided into two distinct OFDM symbols: a first OFDM symbol with a reduced number of sub-carriers optimized for robustness in challenging radio environments, and a second OFDM symbol with a higher number of sub-carriers optimized for spectral efficiency. This segmentation allows each symbol to serve its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the parameter of guard interval length between the two OFDM symbols. The first OFDM symbol uses a longer guard interval to accommodate multipath propagation, while the second OFDM symbol uses a shorter guard interval to maximize spectral efficiency, as the channel conditions are better established by the first symbol.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11456829B2Transmitter and method of transmitting, receiver and method of receiving

Publication Date: 2022.09.27 SATURN LICENSING LLC

AI summary

A receiver for detecting and recovering payload data from a received signal is provided. The receiver includes a detector, a frequency synchronizer, and a demodulator. The receiver is configured to detect the received signal. The received signal includes the payload data and signalling data for use in detecting and recovering the payload data. The frequency synchronizer is configured to process the received signal so as to compensate for a frequency offset in the received signal. The demodulator is configured to detect the one or more first symbols and the one or more second symbols, to recover the signalling data from the one or more first symbols, and to use the signalling data to recover the payload data from the one or more second symbols. The sequence is a signature sequence associated with a transmitter of the received signal.