NOMA WTRU DMRS Subset Selection for Collision Mitigation
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Solution Overview
Problem
In emerging 5G systems, non-orthogonal multiple access (NOMA) transmissions face challenges in collision mitigation and complexity reduction, particularly in scenarios with high path losses and multiple antenna elements, where traditional beamforming techniques are insufficient to ensure reliable communication.
Innovation Solution
A method and apparatus for autonomous transmission in wireless transmit/receive units (WTRUs) that randomly select demodulation reference signal (DMRS) subsets and associated configuration, allowing for grant-based or grant-free transmissions, and using multi-type NOMA request signals (NRS) or scheduling requests (SR) to assist in reducing collisions and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional beamforming techniques are used to compensate severe path loss, then coverage area can be improved, but device complexity and collision likelihood increase in NOMA transmissions
Solution Approach 1:
The DMRS resources are segmented into multiple subsets, where each subset contains multiple DMRS resources. The WTRU randomly selects one subset and then randomly selects one DMRS resource from the selected subset. This segmentation reduces the collision likelihood by distributing the selection space while maintaining comprehensive coverage compensation through beamforming.
Solution Approach 2:
The WTRU performs preliminary random selection of DMRS subset and DMRS resource before actual transmission. This preliminary action with configured subsets reduces collision likelihood at the source, allowing traditional beamforming techniques to effectively compensate path loss without being overwhelmed by collision-related complexity.
2Reliability
If multiple DMRS resources are configured for NOMA transmissions, then reliability can be improved, but collision likelihood increases
Solution Approach 1:
Multiple DMRS resources are organized into multiple subsets. The WTRU first randomly selects one subset and then randomly selects one DMRS resource from the selected subset. This two-stage segmentation maintains reliability by providing multiple diverse options while reducing collision likelihood through the hierarchical selection process.
Solution Approach 2:
The DMRS resource selection is extended from a single-dimension choice to a two-dimensional selection process: first selecting a subset (adding a subset dimension), then selecting a specific resource within the subset. This dimensional expansion increases the total selection space, thereby reducing collision likelihood while maintaining reliability through diverse resource options.
3Productivity
If autonomous transmission type selection is implemented, then spectral efficiency can be improved, but transmission complexity increases
Solution Approach 1:
The WTRU autonomously selects the transmission type (grant-based or grant-free) and the DMRS subset without requiring complex network coordination. This self-service approach improves spectral efficiency by enabling flexible autonomous transmission while the pre-configured DMRS subsets simplify the autonomous decision-making process, thereby reducing the perceived complexity.
Data Source
AI summary
A method and apparatus for performing autonomous transmission for performing collision mitigation and complexity reduction for non-orthogonal multiple access (NOMA) transmissions are disclosed. A wireless transmit/receive unit (WTRU) may receive a configuration with multiple SRs and associated preamble subsets, randomly select a preamble subset and select a SR configuration according to the randomly selected preamble subset based on the received configuration. The WTRU may transmit an SR associated with the selected preamble subset. Next the WTRU may select a preamble from the selected preamble subset, and transmit the selected preamble with a data transmission. Each SR associated with preamble subsets may be distinguished by time and frequency resources, sequence index value, or PUCCH index value.