Asynchronous Bidirectional Cell-Free Network Power Optimization

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Solution Overview

Problem

Existing schemes for asynchronous bidirectional communications in cell-free networks are limited, as they are either applicable only to single-carrier or multi-carrier systems, and lack a unified method to mitigate inter-symbol interference (ISI) across both types of modulation.

Innovation Solution

A bidirectional communication method is proposed that uses cyclic prefix (CP) assisted block transmission and joint pre- and post-channel equalizers at both transceivers to mitigate ISI, while employing an amplify-and-forward (AF) technique at access points and power control at transceivers to optimize beamforming matrices and transmit powers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If existing single-carrier or multi-carrier schemes are used, then ISI mitigation is achieved for specific modulation types, but the solution is not unified and cannot be applied to both single-carrier and multi-carrier systems

Engineering Contradiction:

Improveapplicability to both single-carrier and multi-carrier systemsVSAvoidsystem configuration complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent proposes a unified communication scheme that can operate in both single-carrier and multi-carrier modes using the same system architecture. The joint pre- and post-channel equalizers at TRs and beamforming matrices at APs are designed to work universally across both modulation types, eliminating the need for separate optimized schemes for each mode and thereby resolving the contradiction between versatility and complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If block-wise single-carrier communications with cyclic prefix are used, then ISI between successive information blocks is eliminated, but intra-block interference remains and requires complex optimization

Engineering Contradiction:

ImproveISI elimination between blocksVSAvoidoptimization problem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the communication into blocks with cyclic prefixes to eliminate inter-block ISI, while simultaneously addressing intra-block interference through joint pre- and post-channel equalization. This segmentation approach allows the system to handle ISI in manageable portions while using equalizers to clean up residual interference within blocks, resolving the contradiction between reliability and complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces joint pre- and post-channel equalizers as intermediary components that process the signal between the transmitter and receiver. These equalizers act as mediators to compensate for the intra-block interference caused by the multi-tap channel, enabling the system to achieve both inter-block ISI elimination through cyclic prefixes and intra-block interference mitigation through equalization, thus resolving the complexity-reliability contradiction.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If decode-and-forward strategy is used at APs, then error correction is performed, but computational complexity increases significantly

Engineering Contradiction:

Improveerror correction capabilityVSAvoidcomputational complexity at APs

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the computationally intensive decode-and-forward strategy with an amplify-and-forward strategy at APs. Instead of decoding and re-encoding signals (which requires complex error correction operations), the system amplifies and forwards the received signals using optimized beamforming matrices. This substitution maintains system reliability while significantly reducing the computational burden on APs, resolving the contradiction between error correction capability and computational complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Device complexity

If amplify-and-forward strategy is used, then computational complexity at APs is reduced, but the system must deal with intra-block interference from multi-tap channels

Engineering Contradiction:

Improvecomputational complexity at APsVSAvoidintra-block interference

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250133511A1Asynchronous bidirectional communications in cell free networks

Publication Date: 2025.04.24 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method to minimize a total transmit power in a bidirectional asynchronous cell free network where at least two transceivers, TRs, exchange their information using a number of amplify and forward, AF, based access points, APs, the total transmit power subject to quality of service, QoS constraints on TR data-rates, where the method includes estimating channels between the at least two TRs and the AF-based Aps. The method includes calculating a total power consumption for each channel tap. The method includes determining a single non-zero channel tap which results in a lowest total power consumption. The method includes, based on the single non-zero channel tap determined: calculating beamforming matrices for the APs; calculating a total power transmission of each transceiver of the at least two transceivers; calculating precoding matrices at each transceiver of the at least two transceivers; and calculating post-channel equalizers at the at least two transceivers.