Uplink DMRS Orthogonality via RB Portion Segmentation
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Solution Overview
Problem
In multi-user multiple-input multiple-output (MU-MIMO) systems, non-orthogonal demodulation reference signals (DMRS) due to varying resource block (RB) grants among users cause interference, affecting decoding performance.
Innovation Solution
The proposed solution involves dividing the RB grant into overlapping and non-overlapping portions, generating distinct DMRS sequences for each portion to ensure orthogonality, and using resource allocation types and indicators in downlink control signaling to manage the DMRS sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single DMRS sequence is used for all RBs in MU-MIMO, then device complexity is reduced, but orthogonality is lost causing interference between users
Solution Approach 1:
The patent divides the RB grant into multiple portions (first portion and second portion) and generates separate DMRS sequences for each portion. This segmentation ensures that orthogonal DMRS sequences are maintained for different user equipments while managing complexity through structured sequence generation using different root indices for different RB portions
2Object-affected harmful factors
If multiple DMRS sequences are generated for different RB portions, then orthogonality is improved reducing interference, but device complexity increases
Solution Approach 1:
The patent applies different DMRS sequence generation parameters (different root indices) to different RB portions locally. The first RB portion uses one root index while the second RB portion uses another root index, creating locally optimized orthogonal sequences that reduce interference without requiring complete reconfiguration of the entire DMRS system
3Reliability
If resource allocation type 1 is used to enable multiple DMRS sequences, then orthogonality is achieved, but control signaling complexity increases
Solution Approach 1:
The patent performs preliminary configuration by indicating the resource allocation type and DMRS sequence parameters in advance through downlink control signaling. The network device pre-configures which root indices and RB portions should be used, allowing the terminal to generate orthogonal DMRS sequences without real-time complex calculations, thereby improving decoding performance while managing control signaling complexity
Data Source
AI summary
The present disclosure includes systems and methods for reducing intra-cell interference during uplink MU-MIMO. An uplink grant that allocates a plurality of resource blocks is obtained. A first portion of the plurality of RBs that are overlapping with a set of RBs granted to a second UE is determined. A second portion of the plurality of RBs that are non-overlapping with the set of RBs granted to the second UE is also determined. A first demodulation reference signal (DMRS) sequence is generated for the first portion of the plurality of RBs. A second DMRS sequence is generated for the second portion of the plurality of RBs, where the second DMRS sequence is different than the first DMRS sequence. An uplink transmission (e.g., PUCCH, PUSCH) is generated that includes RBs having different DMRS sequences.