Terminal Equipment Cyclic Shift Alignment for Timing Error Elimination

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Solution Overview

Problem

In LTE mobile communication systems, the existing methods for detecting patterns formed by cyclically shifted Zadoff-Chu sequences result in timing errors due to differences in sampling rates between terminal equipment and base station, complicating channel estimation and demodulation performance.

Innovation Solution

Performing cyclic shifts after inverse fast Fourier transform (IFFT) in terminal equipment and defining cyclic shifts by IFFT output samples ensures that the number of samples for cyclic shifts is an integer, aligning with base station sampling rates, thereby simplifying channel estimation and eliminating timing errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cyclic shifts are performed before inverse Fourier transform (IFFT) in terminal equipment, then the signal processing follows the conventional method, but timing errors occur due to differences in sampling rates between terminal equipment and base station

Engineering Contradiction:

Improvetiming accuracyVSAvoidsignal processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional signal processing order by performing cyclic shifts after IFFT instead of before IFFT. This reversal eliminates timing errors caused by sampling rate differences between terminal equipment and base station, as the cyclic shift is now applied to the time-domain signal at the correct stage in the processing chain

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the processing parameter order by modifying when the cyclic shift operation is applied in the signal processing chain. By changing the sequence from pre-IFFT cyclic shift to post-IFFT cyclic shift, the system achieves accurate timing detection without requiring complex sampling rate synchronization

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If cyclic shifts are defined by non-integer samples, then the terminal equipment can apply flexible cyclic shifts, but timing errors occur in base station detection

Engineering Contradiction:

Improvecyclic shift flexibilityVSAvoidcyclic shift detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent changes the parameter definition by specifying that cyclic shifts must be defined in terms of integer numbers of IFFT output samples. This parameter constraint ensures that the base station can accurately detect cyclic shifts without timing errors, while still maintaining sufficient flexibility for multi-user multiplexing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional approach of applying cyclic shifts in the frequency domain with a time-domain cyclic shift applied after IFFT. This substitution allows the system to use integer sample-based cyclic shifts that are directly detectable by the base station, eliminating the need for complex fractional sample interpolation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If frequency region crosscorrelation method is used for detecting multiple patterns, then the number of circuits is reduced, but timing errors from sampling rate differences complicate the detection

Engineering Contradiction:

Improvedetection circuit complexityVSAvoidpattern detection accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent inverts the detection approach by performing crosscorrelation in the time domain after IFFT rather than in the frequency domain. This time-domain crosscorrelation using integer sample-based cyclic shifts eliminates timing errors and simplifies the detection process while maintaining the ability to detect multiple patterns simultaneously

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent substitutes frequency-domain crosscorrelation with time-domain crosscorrelation. By detecting cyclic shifts in the time domain after IFFT, the system achieves accurate timing detection with simpler circuitry, as the integer sample-based cyclic shifts produce distinct time-domain signatures that are easy to detect

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP1919149B1Mobile communication system transmitting equipment and transmission signal generation method

Publication Date: 2017.04.12 NEC CORP

AI summary

A transmitting equipment is used in a mobile communication system in which a signal obtained by cyclically shifting a predetermined sequence is used for communication. An inverse fast Fourier transform device of the transmitting equipment converts a signal obtained by signal processing on a predetermined sequence in a frequency region into a time region by inverse fast Fourier transform. A cyclic shift device cyclically shifts by a predetermined amount of shift the sequence in the signal converted into the time region by the inverse fast Fourier transform device.