Training Sequence Spreading for VHT MIMO AGC Accuracy

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Solution Overview

Problem

Very High Throughput (VHT) wireless communication systems face challenges in maintaining accurate Automatic Gain Control (AGC) power settings due to significant power variations when using Multiple Input or Multiple Output (MIMO) technology with Spatial-Division Multiple Access (SDMA), which affects the accuracy of power settings for multiple antennas beyond the 4-antenna limit.

Innovation Solution

The solution involves generating modified training sequences for VHT wireless communication, where at least a portion of the training sequence in each spatial stream is multiplied with a different spreading sequence, such as an orthogonal Hadamard sequence, to minimize power differences between the preamble and data packets, while maintaining an 800 ns repetition interval, allowing for accurate AGC settings even with more than 4 antennas.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If MIMO technology with SDMA is used to increase bandwidth and throughput, then data throughput is improved, but power variations between spatial streams increase causing AGC errors

Engineering Contradiction:

Improvedata throughputVSAvoidAGC power setting accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies parameter changes by modifying the training sequence parameters through spreading sequence multiplication. Specifically, the training sequence is multiplied by different spreading sequences for different spatial streams, which changes the power distribution characteristics to minimize power variations and improve AGC accuracy while maintaining high throughput capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The spreading sequence acts as an intermediary element between the training sequence and the spatial stream transmission. By introducing this intermediary spreading sequence, the patent mediates the power variations that would otherwise directly affect AGC accuracy, allowing multiple spatial streams to coexist with different power levels while maintaining accurate AGC settings

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If multiple spatial streams are transmitted simultaneously to increase user capacity, then productivity is improved, but correlation between transmitters increases affecting AGC performance

Engineering Contradiction:

Improveuser capacityVSAvoidcorrelation between transmitters

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces asymmetry by assigning different spreading sequences to different spatial streams. This asymmetric treatment of training sequences across spatial streams breaks the correlation symmetry, allowing each stream to be differentiated at the receiver end while maintaining orthogonal properties that minimize interference and correlation between simultaneous transmissions

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The training sequence is segmented and independently processed for each spatial stream by multiplying with different spreading sequences. This segmentation allows each spatial stream to have its own optimized training characteristics, reducing mutual correlation and enabling accurate AGC performance even when multiple streams are transmitted simultaneously

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If training sequence is modified with spreading sequence to reduce power variations, then AGC accuracy is improved, but device complexity increases

Engineering Contradiction:

ImproveAGC power setting accuracyVSAvoidtraining sequence processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The spreading sequence multiplication is performed as a preliminary action during the training sequence generation phase, before the actual data transmission begins. This preliminary processing of the training sequence allows the receiver to pre-compute the expected power characteristics, simplifying the subsequent AGC operation while still achieving high accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameters of the training sequence through spreading sequence multiplication, which transforms the training sequence into a form that naturally compensates for power variations. This parameter transformation achieves AGC accuracy improvement without requiring complex real-time processing, as the spreading sequences are predetermined and can be stored in lookup tables

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8767524B2Training sequences for very high throughput wireless communication

Publication Date: 2014.07.01 QUALCOMM INC

AI summary

Methods and systems for communications that generate a plurality of spatial streams, wherein each of the spatial streams comprises a data packet with a training sequence; and multiply at least a portion of the training sequence in each of the spatial streams with a different spreading sequence. Methods and systems that receive a plurality of spatial streams, wherein each of the spatial streams comprises a data packet with a training sequence; multiply at least a portion of the training sequence in each of the spatial streams with a different spreading sequence; and decode the plurality of spatial streams based on the different spreading sequences.