Wireless Array Gain Reduction via Subcarrier Power Allocation

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Solution Overview

Problem

Wireless communication devices with multiple antennas face challenges in complying with emission/radiation regulations due to directional gain from beamformed transmissions, leading to potential radiation violations, especially as the number of transmit chains increases.

Innovation Solution

The techniques involve allocating power and applying orthogonal precoding vectors across multiple transmitters to reduce array gain, allowing for efficient use of all transmitter chains while minimizing directional gain, using methods that allocate maximum power to fewer transmitters per subcarrier, apply orthogonal precoding to adjacent subcarriers, and duplicate signals with orthogonal precoding to achieve reduced array gain.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If beamformed transmission from multiple antennas is used, then directional gain and receiver signal strength are improved, but radiation levels in certain directions exceed regulatory limits

Engineering Contradiction:

Improvereceiver signal strengthVSAvoidradiation levels

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The transmission signal is segmented across multiple transmitters and subcarriers, with each subcarrier allocated to only one transmitter at maximum power, preventing constructive interference that would cause high directional gain and radiation levels

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the power allocation parameters by allocating maximum power to only one transmitter per subcarrier rather than distributing power across multiple transmitters, thereby reducing array gain while maintaining total power transmission capability

Inventive Principle:

Principle #35Parameter changes

2Productivity

If multiple transmitter chains are used, then data rates and total power transmission are improved, but array gain increases leading to regulatory compliance issues

Engineering Contradiction:

Improvedata ratesVSAvoidarray gain

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent segments the frequency spectrum into multiple subcarriers and assigns each subcarrier to a different transmitter for maximum power transmission, allowing all transmitter chains to operate at full power without creating harmful array gain effects

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from spatial domain beamforming to frequency domain power allocation, using orthogonal frequency division multiplexing to distribute signals across subcarriers, thereby eliminating directional array gain while maintaining multi-transmitter productivity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS9112555B2Transmit correlated array gain reduction

Publication Date: 2015.08.18 CISCO TECHNOLOGY INC

AI summary

Techniques are presented herein to achieve reduced array gain associated with a transmission made from multiple antennas of a wireless communication device. In accordance with one technique, a wireless communication device is provided having a plurality of transmitters each configured to transmit via a corresponding one of a plurality of antennas. Subcarriers of at least one transmit signal to be weighted across the plurality of transmitters are allocated power so that for each subcarrier, only one transmitter is allocated a maximum power.