Estimating Spatial Expansion Matrix in MIMO Systems

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Solution Overview

Problem

In MIMO wireless communication systems, especially in IEEE 802.11n, the method for spatial expansion of spatial streams is not defined for high throughput transmissions, limiting the utilization of transmitter resources and hindering beamforming and adaptive rate selection without knowledge of the spatial expansion matrix at the receiving device.

Innovation Solution

A wireless communication device derives and estimates the spatial expansion matrix from received transmissions, using channel estimate information and transmit rate data to determine the number of spatial streams, allowing for improved beamforming and rate selection by storing and distributing this information across a centralized controller for use by other devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If spatial expansion is not defined for HT transmissions, then transmitter resources are not fully utilized, but the receiving device cannot improve beamforming or adaptive rate selection without knowledge of the spatial expansion matrix

Engineering Contradiction:

Improvetransmitter resource utilizationVSAvoidspatial expansion matrix information

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The receiving device estimates the spatial expansion matrix by analyzing feedback information from the transmitting device, specifically using the relationship between the number of spatial streams, number of antennas, and transmit rate. This feedback mechanism allows the receiving device to derive the spatial expansion matrix without direct transmission of this information, thereby resolving the contradiction between resource utilization and information availability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The receiving device performs self-service by autonomously estimating the spatial expansion matrix using available channel estimate information and transmit rate data. Instead of relying on the transmitting device to provide this information directly, the receiving device independently derives the spatial expansion matrix through evaluation of the relationship between spatial streams, antennas, and transmission parameters.

Inventive Principle:

Principle #25Self-service

2Productivity

If the number of spatial streams is less than the number of antennas, then spatial expansion is needed to fully utilize transmitter resources, but the spatial expansion method is not defined in IEEE 802.11n

Engineering Contradiction:

Improvetransmitter resource utilizationVSAvoidspatial expansion method definition

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent changes the parameter from explicitly defining spatial expansion methods to estimating spatial expansion matrices based on observable transmission parameters. Instead of specifying fixed spatial expansion methods in the standard, the system dynamically determines spatial expansion matrices by evaluating the relationship between spatial streams, antennas, and transmit rates, thereby avoiding the need for complex standard definitions while maintaining resource utilization.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If spatial expansion matrix information is not known at the receiving device, then beamforming and adaptive rate selection cannot be improved, but transmitting this information increases system complexity

Engineering Contradiction:

Improvebeamforming performanceVSAvoidspatial expansion matrix information management

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary estimation process that derives the spatial expansion matrix from existing transmission parameters rather than directly transmitting the matrix itself. This intermediary approach uses channel estimate information and transmit rate data as mediators to obtain the spatial expansion matrix, improving beamforming performance without the complexity of direct information exchange.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8295384B2Estimating spatial expansion matrix in a MIMO wireless communication system

Publication Date: 2012.10.23 CISCO TECHNOLOGY INC

AI summary

Techniques are provided to derive the spatial expansion matrix used when one wireless communication device sends a transmission with a number of spatial streams less than the number of its transmit antennas to another wireless communication device. These techniques involve, at the receiving wireless communication device, generating channel estimate information for received transmissions sent with different numbers of spatial streams and to determine when sufficient information is available to estimate a spatial expansion matrix for different spatial expansion scenarios.