UE-Specific DMRS Configuration for Cellular Interference Reduction
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Solution Overview
Problem
Current methods fail to achieve sufficient orthogonality between demodulation reference signals (DMRS) from different User Equipments (UEs) in cellular networks, leading to interference and degraded channel estimation, especially in dense traffic and closely located UEs, where existing solutions like Coordinated Multipoint Processing and Orthogonal Cover Codes are ineffective.
Innovation Solution
Assigning UE-specific base sequences and cyclic shift hopping patterns to UEs, allowing them to generate and transmit DMRS based on unique configuration parameters, which substitutes default cell-specific configurations, thereby minimizing interference between DMRS transmissions from different cells and within the same cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cell-specific base sequences and cyclic shift hopping patterns are used for DMRS transmissions, then the configuration is simple and cell-wide orthogonality is achieved, but interference occurs between UEs in different cells and within the same cell
Solution Approach 1:
The patent transitions from cell-specific to UE-specific base sequences and cyclic shift hopping patterns. Each UE is individually configured with unique parameters (base sequence index, cyclic shift values, hopping patterns) to achieve localized orthogonality. This allows the system to maintain simple cell-wide configuration while eliminating interference through UE-specific customization of DMRS parameters.
2Productivity
If co-scheduling is enabled for uplink transmissions from multiple UEs, then network capacity increases, but interference occurs between simultaneous transmissions on the same bandwidth
Solution Approach 1:
The patent enables co-scheduling by dynamically changing DMRS parameters for each UE. Base stations assign different base sequence indices, cyclic shift values, and hopping patterns to co-scheduled UEs. These parameter variations ensure that even when UEs transmit simultaneously on the same bandwidth, their DMRS remain orthogonal, allowing the base station to accurately estimate channels for each UE without interference.
3Measurement precision
If DMRS transmissions are made orthogonal within each cell, then channel estimation accuracy improves, but semi-orthogonal DMRS from neighbouring cells still cause interference
Solution Approach 1:
The patent extends orthogonality from the intra-cell dimension to the inter-cell dimension by introducing UE-specific parameters. While traditional methods achieved orthogonality only within a cell using cell-specific sequences, this patent adds another dimension of differentiation through UE-specific base sequence indices and cyclic shift patterns. This multi-dimensional parameter space ensures that DMRS from different cells remain orthogonal, eliminating cross-cell interference and improving channel estimation accuracy.
Data Source
AI summary
Methods and apparatuses for enabling a configured demodulation reference signal to be transmitted from a User Equipment, UE, (202) when served by a base station (200) in a cellular network. The base station sends (2:3) at least one configuration parameter to the UE, which indicates a UE-specific base sequence and/or a UE-specific cyclic shift hopping pattern assigned (2:2) to the UE. The UE then uses thec onfiguration parameters to generate (2:4) and transmit (2:5) the demodulation reference signal based on the UE-specific base sequence and UE- specific cyclic shift hopping pattern. Thereby, orthogonality can be achieved between the transmitted demodulation reference signal and any demodulation reference signals transmitted by other UEs, by using separate UE-specific base sequences and/or UE-specific cyclic shift hopping patterns.