Uplink DMRS Mapping for UL MU-MIMO Orthogonality
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing uplink Demodulation Reference Signals (DMRS) for supporting high-speed data traffic and multiple user connections, particularly in ensuring orthogonality and flexibility for Uplink Multi-User Multi-Input Multi-Output (UL MU-MIMO) scheduling.
Innovation Solution
A method for generating and mapping uplink DMRS sequences, involving the reception of Downlink Control Information for Physical Uplink Shared Channel (PUSCH) scheduling, where the DMRS sequence is mapped with specific spacing within a symbol to Resource Elements (REs), utilizing cyclic shift and Orthogonal Cover Code (OCC) to ensure orthogonality and efficient resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DMRS sequences are mapped with conventional spacing to support high-speed data traffic and multiple user connections, then system capacity and data transfer rates improve, but orthogonality between multiple users deteriorates
Solution Approach 1:
The DMRS sequence mapping is segmented into two independent dimensions: frequency domain spacing (every 2nd RE) and time domain OCC application (length 2 or 4). This segmentation allows each dimension to independently contribute to orthogonality, enabling multiple users to maintain orthogonality even with increased system capacity and user connections.
Solution Approach 2:
The patent introduces a time domain dimension (OCC - Orthogonal Cover Code) in addition to the frequency domain spacing. By applying OCC across multiple symbols in the time domain, the system creates an additional layer of orthogonality that works independently from frequency spacing, thereby supporting more users without sacrificing orthogonality.
2Reliability
If DMRS sequences are mapped with increased spacing to ensure orthogonality, then orthogonality between users is maintained, but resource utilization and data transfer rates worsen
Solution Approach 1:
By segmenting orthogonality into two dimensions (frequency spacing and time-domain OCC), the patent allows the system to use moderate frequency spacing (every 2nd RE) while compensating with OCC in the time domain. This segmentation prevents the need for excessive frequency spacing that would reduce resource utilization.
Solution Approach 2:
The patent changes the parameter of OCC length (supporting both length 2 and length 4) to flexibly adjust orthogonality. This parameter change allows the system to maintain orthogonality with reasonable frequency spacing, thereby preserving resource utilization and data transfer rates.
3Ease of operation
If conventional DMRS mapping methods are used to support basic uplink transmission, then implementation simplicity is maintained, but flexibility for UL MU-MIMO scheduling is insufficient
Solution Approach 1:
The patent creates a universal DMRS mapping framework that works for both single-user and multi-user scenarios. The same mapping rules (frequency spacing every 2nd RE and OCC application) apply universally, whether for UL MU-MIMO or conventional uplink, thereby maintaining implementation simplicity while enabling scheduling flexibility through OCC-based user differentiation.
Solution Approach 2:
The patent introduces dynamic OCC length selection (length 2 or 4) that can be adapted to different scheduling scenarios. This dynamic parameter allows the system to flexibly support UL MU-MIMO scheduling while maintaining a relatively simple implementation based on existing DMRS mapping structures.
Data Source
AI summary
Disclosed are a method for transmitting and receiving an uplink demodulation reference signal (DMRS) in a wireless communication system, and an apparatus therefore. Particularly, a method by which a terminal transmits a DMRS in a wireless communication system comprises the steps of: receiving, from a base station, downlink control information (DCI) for physical uplink shared channel (PUSCH) scheduling; generating a DMRS sequence for the PUSCH; and mapping the DMRS sequence to a physical resource, wherein the DMRS sequence can be mapped with the spacing of a predetermined resource element (RE) within the symbol to which the DMRS sequence is mapped.