WLAN Receiver Early Power Down via Center Frequency Offset Detection

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Solution Overview

Problem

In WLAN infrastructure mode, receivers consume excessive power waiting for packet destination address verification, as they cannot determine if a packet is intended for them until the layer 2 destination address is read, leading to unnecessary power usage for non-intended packets.

Innovation Solution

A power-saving receiver that measures and compares the center frequency offset (CFO) during the preamble interval with a stored CFO table, powering down if the difference exceeds a threshold, thereby reducing power consumption by determining non-intended packets earlier than traditional methods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the receiver processes packets until the layer 2 destination address is verified, then the packet can be correctly identified, but power consumption increases significantly

Engineering Contradiction:

Improvepacket identification accuracyVSAvoidreceiver power consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The receiver performs preliminary actions during the preamble interval by measuring the center frequency offset and comparing it with stored CFO values to determine early whether a packet is intended for this station. This preliminary frequency-based filtering allows the receiver to power down before fully processing the packet header, thereby reducing power consumption while maintaining accurate packet identification through the CFO table lookup mechanism

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The packet processing is segmented into distinct phases: preamble processing with CFO measurement, CFO table comparison, and full packet processing. By segmenting the processing and enabling early termination based on CFO mismatch, the receiver avoids unnecessary processing of non-intended packets, resolving the contradiction between complete packet verification and power consumption

Inventive Principle:

Principle #1Segmentation

2Reliability

If the receiver processes all packets fully to verify destination address, then no packets are missed, but power consumption increases for non-intended packets

Engineering Contradiction:

Improvepacket reception reliabilityVSAvoidenergy wasted on non-intended packets

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system performs preliminary verification using the center frequency offset measurement during the preamble interval and compares it against the CFO table. This preliminary check provides a reliable early indication of whether a packet is intended for this station, allowing the receiver to maintain high reliability by only fully processing packets with matching CFO values while minimizing energy waste on non-intended packets

Inventive Principle:

Principle #10Preliminary action

3Use of energy by moving object

If the receiver powers down earlier to save power, then energy consumption decreases, but packet identification may be inaccurate

Engineering Contradiction:

Improvereceiver power consumptionVSAvoidpacket destination identification accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The receiver performs preliminary packet screening based on center frequency offset measurement during the preamble interval and compares the measured CFO with stored values in the CFO table. This preliminary action enables early power down for non-matching packets while maintaining accurate packet identification through the CFO-based filtering mechanism, thus resolving the contradiction between early power saving and identification accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The CFO table acts as an intermediary structure that stores pre-measured center frequency offset values for intended transmitters. By using this intermediary table for comparison during preamble processing, the system achieves accurate packet identification without requiring full packet processing, enabling early power down while maintaining reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11627531B2WLAN receiver early power down based on center frequency offset detection

Publication Date: 2023.04.11 SILICON LABORATORIES INC

AI summary

A wireless local area network (WLAN) station receiver has a center frequency offset (CFO) estimator and an CFO table with an association between a CFO value from a recently received access point packet for which the station is associated according to 802.11. The receiver performs a comparison between the CFO estimate of the received packet and the CFO value from the CFO database, and powers the receiver down if the comparison exceeds a threshold. The threshold may be an absolute value in parts per million, or may include a time drift compensation component.