DMRS Port Selection for 2-Step Random Access
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Solution Overview
Problem
The existing 2-step random access procedure in wireless communications faces challenges in defining the behavior and methods for Demodulation Reference Signal (DMRS) design for Physical Uplink Shared Channel (PUSCH) in msgA, particularly in minimizing DMRS collisions and ensuring reliable transmission across multiple wireless devices.
Innovation Solution
The proposed solution involves determining a subset of DMRS ports based on code-division multiplexing groups, where the selection interleaves antenna ports starting from the smallest index value within each group, and using specific DMRS sequence initializations tied to PRACH occasions or PUSCH resource units to minimize interference and maximize orthogonality among DMRS signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DMRS ports are allocated without systematic selection from CDM groups, then DMRS configuration is simple, but DMRS collisions increase and reliability decreases
Solution Approach 1:
The DMRS ports are segmented into multiple CDM (Code Division Multiplexing) groups, where each group contains specific ports. The method systematically selects one port from each CDM group based on the WD's identifier, ensuring diversified port selection across groups. This segmentation approach reduces collisions by distributing WDs across different port subsets while maintaining manageable complexity through standardized selection rules within each group.
Solution Approach 2:
The invention changes the parameter selection approach by using WD-specific parameters (such as WD ID, PRACH occasion index, or PUSCH resource unit index) to determine which DMRS port from each CDM group should be used. This parameter-based selection dynamically assigns ports based on WD characteristics, reducing the probability of collisions while following systematic procedures that control complexity.
2Productivity
If the number of DMRS sequences is limited, then sequence initialization is simple, but the capacity to support multiple WDs simultaneously decreases
Solution Approach 1:
The invention extends the DMRS sequence differentiation from a single dimension to multiple dimensions by combining: (1) different CDM group selections, (2) different port selections within groups, and (3) different sequence initializations based on WD-specific parameters. This multi-dimensional approach exponentially increases the number of unique DMRS configurations available, supporting more simultaneous WDs without requiring a proportional increase in base sequence count.
Solution Approach 2:
The DMRS configuration space is segmented into multiple CDM groups, each offering independent port selection. This segmentation creates multiple pathways for WD differentiation, where each WD can be uniquely identified by its combination of selected ports across groups and its sequence initialization parameters, thereby increasing system capacity through structured diversity.
3Ease of operation
If DMRS ports are selected without considering CDM groups, then port allocation is straightforward, but mutual interference among DMRS signals increases
Solution Approach 1:
By segmenting DMRS ports into CDM groups and systematically selecting one port per group for each WD, the invention ensures that WDs are distributed across different orthogonal code resources. This segmentation approach maintains operational simplicity through rule-based selection while inherently reducing interference by exploiting the orthogonal properties of CDM groups.
Solution Approach 2:
The invention applies local quality differentiation by assigning WDs to specific ports within CDM groups based on their unique parameters. Each WD receives a locally optimized port assignment that minimizes its interference with others, while the overall system maintains simplicity through the standardized local selection rule applied uniformly across all WDs.
Data Source
AI summary
Methods and apparatuses are disclosed for Physical Uplink Shared Channel (PUSCH) Demodulation Reference Signal (DMRS) design in, e.g., 2-step random access. In one embodiment, a wireless device configured to communicate with a network node is provided. The wireless device is configured to: receive an indication indicating at least one Demodulation Reference Signal, DMRS, parameter for a physical uplink shared channel, PUSCH in a 2-step random access procedure where the at least one DMRS parameter indicating a plurality of DMRS ports, and determine a subset of the plurality of DMRS ports for the PUSCH in the 2-step random access procedure.