MIMO Phase-Shifter Precoding for Low-Cost CSI-Free Transmission

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Solution Overview

Problem

Current MIMO antenna systems face challenges in efficiently managing multiple antenna elements, particularly in reducing costs associated with high-resolution Digital-to-Analog Converters (DACs) and linear power amplifiers, which scale exponentially with the number of antennas, and require innovative solutions for transmission without Channel State Information (CSI) in massive multiuser scenarios.

Innovation Solution

The implementation of finite-resolution RF/baseband phase-shifters and switches for beamforming, enabling constant-envelope precoding and non-linear symbol-level precoding, allowing for joint transmission of unicast and broadcast signals over shared or non-overlapping time-frequency resources using low-resolution components, thereby reducing the complexity and cost of the transmitter architecture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high-resolution Digital-to-Analog Converters (DACs) and linear power amplifiers are used in MIMO antenna systems, then transmission performance is improved, but system cost and power consumption increase exponentially with the number of antennas

Engineering Contradiction:

Improvetransmission performanceVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces expensive high-resolution DACs and linear power amplifiers with inexpensive low-resolution DACs (1-4 bits) and non-linear power amplifiers. Each antenna element uses a cheap low-resolution DAC combined with a phase shifter and switch, eliminating the need for costly high-resolution components while maintaining acceptable transmission performance through digital precoding techniques

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the resolution parameter of DACs from high (traditionally 12-16 bits) to low (1-4 bits), and changes the power amplifier operation mode from linear to non-linear. This parameter change fundamentally alters the system architecture, allowing cost reduction while maintaining performance through digital signal processing compensation

Inventive Principle:

Principle #35Parameter changes

2Reliability

If high-resolution Digital-to-Analog Converters (DACs) and linear power amplifiers are used in MIMO antenna systems, then transmission performance is improved, but power consumption increases exponentially with the number of antennas

Engineering Contradiction:

Improvetransmission performanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent replaces power-hungry linear power amplifiers with efficient non-linear power amplifiers operating in saturation mode. Low-resolution DACs consume significantly less power than high-resolution counterparts, and the combination with phase shifters and switches creates a power-efficient transmitter architecture suitable for massive MIMO systems

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent employs time-division multiplexing where switches connect different antenna elements to the power amplifier in periodic time slots. Each antenna element is activated periodically rather than simultaneously, allowing the use of efficient non-linear power amplifiers that can operate at full power only when needed, reducing overall power consumption

Inventive Principle:

Principle #19Periodic action

3Productivity

If beamforming is implemented in massive MIMO systems, then transmission efficiency is improved, but the requirement for Channel State Information (CSI) increases system complexity

Engineering Contradiction:

Improvetransmission efficiencyVSAvoidCSI requirement

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent performs digital precoding in the digital domain before DAC conversion, pre-processing the signals to account for channel conditions. This preliminary digital signal processing enables beamforming without requiring real-time CSI feedback for analog beamforming adjustments, reducing system complexity while maintaining transmission efficiency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex analog beamforming mechanisms that require continuous CSI feedback and dynamic phase shifter adjustments with digital precoding. The digital domain processing substitutes for analog beamforming, eliminating the need for complex CSI management while achieving similar or better transmission efficiency through algorithmic signal processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP3719927B1Transmitting method in multiple input multiple output antenna system

Publication Date: 2023.10.11 NOKIA TECHNOLOGIES OY

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AI summary

There is provided a method in a network node for controlling multiple input multiple output antenna system, the method comprising: obtaining a plurality of time domain symbols to be transmitted, the plurality of time domain symbols comprising time domain symbols to be broadcasted via the multiple input multiple output antenna system; determining a mapping between the plurality of time domain symbols and parameters of control units associated with respective antenna elements of the multiple input multiple output antenna system, each control unit comprising a phase shifter, wherein the parameters control values of the phase shifters, and wherein the mapping is performed based on an algorithm for minimizing distortion and/or bit error rate at receiving user equipment; causing applying the parameters at the control units; and causing transmission of the plurality of time domain symbols via the multiple input multiple output antenna system.