MU-MIMO Pilot Orthogonality via Four-Dimensional Walsh Codes
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Solution Overview
Problem
In MU-MIMO communication systems, pseudo-orthogonality of pilots occurs when the number of streams exceeds two, leading to interference issues, and existing solutions like Scrambling identity (SCID) and Walsh codes are insufficient to maintain orthogonality, especially for more than two streams, resulting in reduced performance.
Innovation Solution
Constructing k streams of SU-MIMO pilot and data based on the total number of MU-MIMO streams, modifying demodulation pilot port parameters, and transmitting these streams to terminals, where virtual demodulation pilot ports and synchronized SCID values ensure orthogonality, avoiding pseudo-orthogonality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of MU-MIMO streams exceeds two, then the system throughput is improved, but pseudo-orthogonal pilots occur due to the combination of SCID and two-dimensional Walsh code, leading to interference
Solution Approach 1:
The patent changes the dimensionality parameter of the Walsh code from two-dimensional to four-dimensional. This parameter change enables the system to support more orthogonal pilot ports (up to 4) while maintaining pilot orthogonality, thereby allowing more MU-MIMO streams to be transmitted without generating pseudo-orthogonal pilot interference
Solution Approach 2:
The patent transitions from using two-dimensional Walsh codes to four-dimensional Walsh codes. This dimensional expansion provides additional orthogonal sequences, enabling the system to distinguish more terminal signals on the same time-frequency resource without interference, thus resolving the pseudo-orthogonality problem when streams exceed two
2Manufacturing precision
If four-dimensional Walsh code is used to distinguish more than two streams, then orthogonal demodulation pilot ports are obtained, but the terminal cannot recognize the four-dimensional Walsh code for transparent MU-MIMO
Solution Approach 1:
The patent performs preliminary configuration by pre-defining the mapping relationship between codewords and demodulation reference signal ports. This preliminary action enables terminals to recognize and correctly identify the four-dimensional Walsh code patterns without requiring complex real-time processing, thus maintaining both pilot orthogonality and terminal recognition capability
Solution Approach 2:
The patent introduces a predetermined mapping relationship as an intermediary between the four-dimensional Walsh code and terminal recognition. This mapping acts as a bridge that translates the complex four-dimensional code structure into recognizable patterns for terminals, enabling transparent MU-MIMO operation while maintaining orthogonality
3Object-generated harmful factors
If pre-coding technology is employed to perform pre-processing on data of multiple terminals, then terminal interference is avoided, but the system complexity increases
Solution Approach 1:
The patent segments the interference mitigation function into two parts: (1) using four-dimensional Walsh codes to provide orthogonal pilot sequences for different terminals, and (2) using predetermined codeword-to-port mapping to enable terminal recognition. This segmentation reduces the complexity of pre-processing by leveraging code orthogonality rather than complex signal processing
Data Source
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AI summary
Disclosed are method, device and system for transmitting MU-MIMO pilot and data. The method includes when at least two terminals transmit MU-MIMO pilot and data on one same time/frequency resource, constructing a k-stream SU-MIMO pilot and data; based on the configuration mode of the k-stream SU-MIMO pilot, modifying demodulation pilot port parameters of the at least two terminals; and based on the transmission mode of the k-stream SU-MIMO pilot and data, transmitting the k-stream SU-MIMO pilot and data to the at least two terminals object is to provide method, device and system for transmitting MU-MIMO pilot and data, in which a corresponding k-stream SU-MIMO pilot and data may be constructed and transmitted to at least two terminals, according to the total number of streams k that at least two terminals transmit MU-MIMO pilot and data on one same time/frequency resource, thereby effectively avoiding pseudo-orthogonality of MU-MIMO pilot.