NOMA UE ID Division for DMRS Collision Reduction
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Solution Overview
Problem
In wireless communication systems employing non-orthogonal multiple access schemes, collisions occur in codewords due to the mapping of DMRS and C-RNTI, leading to inefficient data transmission and increased collision ratios, especially when the number of UEs exceeds the available DMRS resources.
Innovation Solution
A method is proposed where the UE ID is divided into multiple fields to select different DMRS signals through modulo operations, allowing for sequential transmission attempts using multiple reference signals, thereby reducing collision ratios and optimizing resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If DMRS and codeword are mapped for each index in legacy NOMA scheme, then data transmission is simplified, but collision occurs in codeword when collision occurs in DMRS
Solution Approach 1:
The UE ID is divided into multiple fields (first field, second field, third field, fourth field) to independently select different DMRS signals. This segmentation allows the system to differentiate between multiple UEs even when they share the same time-frequency resource, thereby reducing codeword collision while maintaining simplified mapping procedures.
2Ease of operation
If UE selects DMRS based on C-RNTI, then DMRS selection is simplified, but collision occurs repeatedly when values obtained through module operation with C-RNTI are identical
Solution Approach 1:
The C-RNTI-based DMRS selection is enhanced by segmenting the UE ID into multiple fields. Each field independently selects a DMRS signal through modulo operation, providing multiple selection dimensions. This maintains the simplicity of UE-autonomous selection while significantly reducing the probability of repeated collisions by distributing UEs across multiple DMRS resources.
Solution Approach 2:
The system transitions from single-dimension DMRS selection (based solely on C-RNTI) to multi-dimensional selection by dividing UE ID into multiple fields. Each field operates in a different dimension of the DMRS selection space, expanding the resource allocation dimensionality and reducing collision probability without complicating the selection mechanism.
3Productivity
If multiple UEs use the same time-frequency resource in NOMA, then resource utilization increases, but collision occurs without sufficient DMRS differentiation
Solution Approach 1:
By segmenting the UE ID into multiple fields that independently select DMRS signals, the system can support multiple UEs on the same time-frequency resource with differentiated reference signals. This enables higher resource utilization while maintaining reliable data transmission through reduced collision probability.
Solution Approach 2:
The system changes the parameter of DMRS differentiation by using multiple fields from UE ID instead of a single C-RNTI value. This parameter change allows for finer granularity in DMRS allocation, enabling more UEs to share the same time-frequency resources with sufficient differentiation to avoid collisions.
Data Source
AI summary
Provided are a method and a device for performing communication using a non-orthogonal code multiple access scheme in a wireless communication system. A terminal divides a terminal identifier into a first field, a second field, a third field and a fourth field and selects a first reference signal based on the first field and a maximum number of reference signals, a second reference signal based on the second field and the maximum number of reference signals, a third reference signal based on the third field and the maximum number of reference signals, and a fourth reference signal based on the fourth field and the maximum number of reference signals. Based on the first reference signal, the second reference signal, the third reference signal or the fourth reference signal, the terminal transmits contention-based data to a base station.