Cyclic Shift Diversity Detection via Channel Impulse Response Analysis

Solution Overview

Problem

Cyclic Shift Diversity (CSD) modes in IEEE 802.11 standards complicate accurate round-trip time (RTT) measurements for mobile device positioning due to multiple possible start times and multipath effects, leading to uncertainties in signal reception and positioning accuracy.

Innovation Solution

A method and apparatus for determining CSD mode using channel impulse response (CIR) analysis, which involves receiving OFDM symbols, computing CIR samples, finding local maxima, and selecting the appropriate CSD mode based on these maxima to differentiate between CSD signals and multipath signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If CSD modes are used to improve signal reception through spatial spreading, then reception quality is improved, but RTT measurement accuracy deteriorates due to multiple possible start times

Engineering Contradiction:

Improvesignal reception qualityVSAvoidRTT measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The system performs preliminary detection of CSD mode presence before conducting RTT measurements. By analyzing the received signal for CSD characteristics (such as cyclic shifts and spatial spreading patterns), the system identifies whether CSD is being used and configures the RTT measurement process accordingly, preventing measurement errors before they occur

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary detection and identification mechanism that acts as a mediator between CSD signal reception and RTT measurement. This intermediary process analyzes signal characteristics to distinguish CSD transmissions from ordinary transmissions, enabling the system to properly interpret RTT measurements even when CSD is employed

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If cyclic shifting is enabled for spatial spreading, then reception reliability is improved, but signal timing identification becomes ambiguous

Engineering Contradiction:

Improvereception reliabilityVSAvoidsignal timing identification accuracy

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary detection of CSD mode presence before conducting RTT measurements. By analyzing the received signal for CSD characteristics (such as cyclic shifts and spatial spreading patterns), the system identifies whether CSD is being used and configures the RTT measurement process accordingly, preventing measurement errors before they occur

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of trying to directly measure timing from CSD signals (which is ambiguous), the system inverts the approach by first detecting the absence of CSD characteristics. When no CSD patterns are detected, the system proceeds with standard timing measurement, effectively using negative detection to resolve the timing ambiguity

Inventive Principle:

Principle #13The other way round (Inversion)

3Area of stationary object

If multipath effects are present in CSD transmission, then signal coverage is improved, but RTT measurement reliability deteriorates

Engineering Contradiction:

Improvesignal coverage areaVSAvoidRTT measurement reliability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent introduces an intermediary detection and identification mechanism that acts as a mediator between CSD signal reception and RTT measurement. This intermediary process analyzes signal characteristics to distinguish CSD transmissions from ordinary transmissions, enabling the system to properly interpret RTT measurements even when CSD is employed

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system uses feedback from signal characteristic analysis to adjust RTT measurement processing. By continuously monitoring for CSD patterns and adapting the measurement approach based on detected signal characteristics, the system maintains RTT measurement reliability despite the presence of multipath effects in CSD transmissions

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP2898338B1Cyclic shift delay detection using a channel impulse response

Publication Date: 2018.11.21 QUALCOMM INC

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AI summary

Systems, apparatus and methods for determining a cyclic shift diversity (CSD) mode are presented. Examples use a channel impulse response (CIR) to determine a current CSD mode. Specifically, a channel impulse response from an orthogonal frequency-division multiplexing (OFDM) symbol, which forms CIR samples. The CIR samples are examined to find a local maxima. A current CSD mode may be selected based on the local maxima found in the CIR samples.