OFDM Receiver Guard Interval Reuse for ICI Cancellation

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Solution Overview

Problem

OFDM receivers in mobile TV applications face performance limitations due to inter-carrier interference (ICI) in time-varying channels, especially in mobile environments like cars and buses, where accurate channel estimation is challenging, and conventional ICI cancellation methods may degrade signal-to-noise ratio (SNR) and increase error rates.

Innovation Solution

The proposed solution involves a GI combiner that reuses the guard interval (GI) of an OFDM signal by combining it with a duplicate section, using weighting coefficients to maximize the signal-to-noise ratio (SNR), and incorporates an equalizer with ICI cancellation circuits like MMSE or DFE to effectively cancel ICI, allowing simultaneous use with conventional ICI cancellation schemes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a long guard interval is used to handle multi-path delay spread, then reliability is improved, but loss of time increases due to transmission of redundant data

Engineering Contradiction:

ImprovereliabilityVSAvoidloss of time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent recovers and reuses the guard interval data that would otherwise be discarded. The GI combiner combines the guard interval with a duplicate section of the active symbol, allowing the receiver to utilize the redundant GI data for improving channel estimation and ICI cancellation rather than simply discarding it as conventional receivers do.

Inventive Principle:

Principle #34Discarding and recovering

2Object-affected harmful factors

If conventional ICI cancellation methods are used, then inter-carrier interference is reduced, but signal-to-noise ratio deteriorates and error rates increase

Engineering Contradiction:

Improveinter-carrier interferenceVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent merges the guard interval data with a duplicate section of the active symbol in the GI combiner. This combining operation creates a enhanced signal that preserves useful information from both sources, allowing subsequent ICI cancellation to operate on improved signal data rather than degraded data, thus maintaining higher SNR while still canceling ICI.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If guard interval is reused by combining with duplicate section, then signal-to-noise ratio is improved, but device complexity increases

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the received signal processing into distinct functional blocks: a GI combiner that combines guard interval data with duplicate sections, and an equalizer with ICI cancellation circuits. This segmentation allows the complexity to be organized and managed through modular components, making the enhanced processing achievable without overwhelming system complexity.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8000417B1Methods and OFDM receivers providing inter-carrier interference cancellation with guard interval reuse scheme

Publication Date: 2011.08.16 SAMSUNG ELECTRONICS CO LTD

AI summary

An OFDM (orthogonal frequency-division multiplexing) receiver circuit can include a GI (Guard Interval) combiner circuit that is configured to adaptively combine data in the GI of an OFDM formatted signal with data included in a predetermined section of an active OFDM symbol.