OFDM Timing Synchronization via Deconvolution for Non-Consecutive Pilot Subcarriers

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Solution Overview

Problem

Existing OFDM and OFDMA systems face challenges in reliably determining timing synchronization due to non-consecutive and non-uniformly spaced subcarriers, leading to interference and incorrect time delay estimation, which results in inter-symbol interference (ISI).

Innovation Solution

The method involves using deconvolution to construct the channel impulse response and identify the first arriving path of a ranging signal, allowing for accurate time delay determination by transforming the received signal into the frequency domain and applying inverse FFT and deconvolution techniques with a known pilot position mask.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If peak detection is used to determine time delay in OFDM ranging, then the method is simple, but the first arriving path cannot be reliably identified leading to incorrect timing

Engineering Contradiction:

Improvesimplicity of peak detection methodVSAvoidaccuracy of time delay estimation

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

Instead of directly detecting peaks in the received signal to determine time delay, the patent inverts the approach by using deconvolution to reconstruct the channel impulse response. This allows identification of the first arriving path through the deconvolved signal rather than direct peak detection, resolving the contradiction between simplicity and accuracy.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces deconvolution as an intermediary process between the received signal and time delay determination. By constructing the channel impulse response through deconvolution, the system can accurately identify the first arriving path without directly analyzing the complex received signal peaks, thus improving measurement precision while maintaining operational feasibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If non-consecutive and non-uniformly spaced subcarriers are used in OFDMA, then resource allocation flexibility is improved, but interference and multipath fading make ranging code isolation difficult

Engineering Contradiction:

Improveflexibility of subcarrier assignmentVSAvoidreliability of ranging code isolation

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent extracts the channel impulse response information from the complex received signal by using deconvolution. This allows the system to isolate the first arriving path and determine time delay accurately, even when non-consecutive and non-uniformly spaced subcarriers are used, thus maintaining reliability while preserving subcarrier assignment flexibility.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces traditional peak detection mechanisms with a deconvolution-based approach. This substitution allows the system to handle non-consecutive and non-uniformly spaced subcarriers effectively, as the deconvolution process can reconstruct the channel characteristics without relying on regular subcarrier patterns, thereby maintaining both flexibility and reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If conventional ranging processes are used with non-consecutive subcarriers, then the system can accommodate flexible resource allocation, but inter-symbol interference is generated due to wrong timing

Engineering Contradiction:

Improveflexibility of resource allocationVSAvoidinter-symbol interference

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces conventional peak detection with deconvolution-based time delay estimation. This substitution enables accurate identification of the first arriving path, providing correct timing information that prevents inter-symbol interference while allowing flexible non-consecutive subcarrier allocation for resource distribution.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces deconvolution as an intermediary step that reconstructs the channel impulse response. This intermediary process provides accurate timing information by identifying the first arriving path, thereby eliminating the source of inter-symbol interference while preserving the flexibility of non-consecutive subcarrier resource allocation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7881392B2OFDM/OFDMA timing synchronization using non-consecutive pilot subcarrier assignment

Publication Date: 2011.02.01 TCL COMMUNICATION TECHNOLOGY HOLDINGS LTD

AI summary

Systems and methods which are adapted determine timing with respect to an orthogonal frequency division (OFD) channel, such as may be used with respect to an OFDM or OFDMA systems through reliably identifying timing of a first arriving signal path. Embodiments use deconvolution to construct the channel impulse response associated with a received signal. The first arriving path for the received signal may readily and reliably be determined using the channel impulse response information.