Random Access DMRS Sequence Mapping for Collision Reduction
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Solution Overview
Problem
In 4G and 5G wireless networks, the random access procedure for uplink synchronization between user equipment (UE) and base stations faces challenges such as DMRS collision due to the lack of efficient mapping between preamble and payload indexes, leading to resource inefficiency and potential synchronization failures.
Innovation Solution
The method involves determining a parameter based on the preamble index to generate a de-modulation reference signal (DMRS) sequence for transmitting a payload, using pre-defined mapping methods to select the appropriate DMRS sequence, thereby reducing DMRS collision and improving resource utilization. This is achieved by using parameters like NIDnSCID, nSCID, or nIDRS, and applying transform precoding techniques to ensure unique DMRS sequences for each preamble.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a random access procedure is performed without efficient mapping between preamble and payload indexes, then the random access procedure can be executed, but DMRS collision occurs leading to resource inefficiency and potential synchronization failures
Solution Approach 1:
The patent applies preliminary action by pre-defining mapping relationships between preamble indexes and DMRS sequences before the random access procedure executes. The UE determines the DMRS sequence based on the preamble index it selects, ensuring that the mapping is established in advance rather than during the access procedure, which prevents DMRS collision and improves synchronization reliability
Solution Approach 2:
The patent changes the parameter mapping relationship between preamble indexes and DMRS sequences by introducing specific formulas (e.g., parameter=(preamble root index−1)*64+[Preamble index/NS]*NS) that map preamble indexes to unique DMRS sequences. This parameter transformation ensures that different preambles are mapped to different DMRS sequences, eliminating collisions and improving both reliability and resource efficiency
2Productivity
If multiple preambles are transmitted in an occasion, then the random access capacity is increased, but DMRS collision probability increases without proper mapping
Solution Approach 1:
The patent applies segmentation by dividing the DMRS sequence space into multiple segments, each associated with a specific preamble index range. The mapping formula segments the total number of preambles (Np) into groups that map to different DMRS sequences, ensuring that even when multiple preambles are transmitted in an occasion, each preamble maps to a unique DMRS sequence segment, preventing collisions while maintaining high access capacity
Solution Approach 2:
The patent introduces an additional dimension to the mapping relationship by using both the preamble root index and preamble index to determine the DMRS sequence parameter. This two-dimensional mapping (root index × preamble index) expands the DMRS sequence space, allowing more preambles to be supported without increasing collision probability, thus improving both capacity and reliability
Data Source
AI summary
Wireless communication includes a user equipment that transmits a message to a base station that includes a preamble and a payload corresponding to the preamble in a random access procedure. A parameter is determined based on the preamble, and a de-modulation reference signal (“DMRS”) sequence that is used for transmitting the payload is generated based on the parameter.