MIMO Precoding for Interference Suppression in Base Stations
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Solution Overview
Problem
Current massive MIMO communication systems are limited by interference, which increases with the number of terminals, restricting the number of devices that can be accommodated in a base station without compromising communication speed.
Innovation Solution
The method involves dividing terminals into groups and using orthogonal codes for multiplexing, followed by pre-coding with a specific matrix to suppress interference, allowing for higher-order modulation and increased channel capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of terminals accommodated in a base station is increased, then the system capacity and service coverage are improved, but the interference between terminals increases and communication quality deteriorates
Solution Approach 1:
The patent divides terminals into multiple groups (first group and second group) and assigns different orthogonal codes to each group. This segmentation allows the system to accommodate more terminals by organizing them into structured groups, where interference within groups is managed through group-specific precoding matrices. The channel matrix is also segmented into blocks corresponding to different terminal groups, enabling targeted interference suppression for each group while maintaining overall system capacity.
Solution Approach 2:
The patent introduces orthogonal codes as an intermediary mechanism between terminals to suppress interference. By assigning orthogonal codes to different terminal groups and using these codes in the precoding process, the system creates a structured interference suppression mechanism. The orthogonal codes act as mediators that enable the base station to differentiate between terminal groups and apply appropriate precoding, thereby reducing mutual interference while accommodating a larger number of terminals.
2Reliability
If orthogonal codes are assigned to all terminals for interference suppression, then the communication quality is improved, but the system complexity and resource overhead increase
Solution Approach 1:
Instead of assigning orthogonal codes to every terminal individually, the patent segments terminals into groups and assigns orthogonal codes at the group level. This reduces the total number of orthogonal codes required from Nv (number of terminals) to 2 (number of groups). The precoding matrix is also segmented into blocks, where only diagonal blocks contain orthogonal code-based interference suppression, while non-diagonal blocks are set to zero, significantly reducing computational complexity.
Solution Approach 2:
The patent applies orthogonal code-based interference suppression partially rather than completely to all terminal pairs. By focusing the precoding operation on diagonal blocks (within-group interference suppression) and setting non-diagonal blocks to zero (between-group interference), the system achieves significant interference suppression with reduced computational burden, avoiding the excessive complexity of full orthogonal code assignment to all terminals.
3Object-affected harmful factors
If the number of antennas at the base station is increased to reduce interference, then the interference suppression capability is improved, but the system cost and hardware complexity increase
Solution Approach 1:
The patent changes the parameter of interference suppression from physical antenna multiplication to mathematical signal processing. By using orthogonal codes and block diagonal precoding matrices, the system achieves interference suppression through parameter optimization in the signal domain rather than increasing hardware in the physical domain. This maintains the existing antenna configuration while improving interference suppression capability through clever signal processing techniques.
Data Source
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AI summary
A MIMO communication method for performing MIMO communication between a base station including a plurality of antennas, and a plurality of terminals accommodated in the base station. The method includes, in the base station, dividing the plurality of terminals into a first and a second group, and assigning orthogonal codes with each other to the respective groups, spreading transmission data to the plurality of terminals with the assigned codes, multiplying data obtained by the spreading by a predetermined pre-coding matrix, obtaining a channel matrix representing channels between the plurality of antennas and the plurality of terminals, multiplying data obtained by the multiplying by the pre-coding matrix by a complex conjugate matrix of the channel matrix, and transmitting data obtained by the multiplying by the complex conjugate matrix from the plurality of antennas.