MU-MIMO Precoding for Diversity Gain
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Solution Overview
Problem
Existing MU-MIMO downlink precoding methods, such as BD and NL-BMD, suffer from reduced signal-to-noise power ratio (SNR) when users close in distance are excluded for IUI cancellation, leading to decreased transmission diversity gain.
Innovation Solution
A transmission device and communication system that employs a precoding computation method allowing the next user as the IUI user, hierarchizing the multi-user space by selecting an additional user for IUI cancellation, thereby enhancing transmission diversity gain through block bi-diagonalization and non-linear processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If block diagonalization (BD) method is used for IUI cancellation, then inter-user interference is eliminated, but desired power is greatly reduced
Solution Approach 1:
The patent applies partial action by selectively canceling IUI only for specific users rather than all users. The base station identifies users experiencing strong IUI and applies precoding cancellation only to those cases, preserving desired power for users who do not require cancellation while still eliminating IUI where needed.
Solution Approach 2:
The patent implements local quality by applying different processing strategies to different users based on their specific channel conditions. Users with strong IUI receive precoding cancellation processing, while other users receive standard precoding, optimizing the balance between IUI elimination and desired power preservation for each user individually.
2Reliability
If block multi-diagonalization (BMD) method is used to secure diversity gain, then transmission diversity is improved, but residual IUI occurs
Solution Approach 1:
The patent employs feedback mechanisms where user terminals report channel state information and IUI levels back to the base station. Based on this feedback, the base station dynamically determines which users require IUI cancellation and adjusts precoding matrices accordingly, enabling adaptive balance between diversity gain and IUI suppression.
Solution Approach 2:
The patent implements dynamic processing where the precoding strategy changes based on current channel conditions. The base station continuously updates precoding matrices based on reported channel states, switching between BMD for diversity and BD for IUI cancellation as conditions require, rather than using a fixed approach.
3Ease of operation
If precoding is applied to all users for complete IUI removal, then receiver configuration can be simplified, but antenna degree of freedom is consumed
Solution Approach 1:
The patent applies partial action by providing simplified receiver configuration only to users who experience strong IUI, while other users can use more advanced interference cancellation techniques. This selective approach reduces the overall antenna degree of freedom consumption compared to applying precoding to all users.
Data Source
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AI summary
A transmission device to be applied to a communication system configured to carry out multi-user MIMO downlink communication, includes a precoder configured to apply transmission precoding processing, a nonlinear processor configured to carry out successive interference cancellation, a beam forming controller configured to form a plurality of beams and to control a beam radiation direction, and a user ordering processor configured to estimate a positional relationship among the plurality of user terminals from radiation direction information on each of the beams, order users in ascending order of a distance from a specific user, and determine a pairing of a transmission target user and an interference permissible user. The precoder determines two users of the transmission target user and the interference permissible user for each user based on the pairing result, and carries out null steering for users other than the two users, to thereby carry out the transmission precoding processing.