DM-RS Group-Hopping Patterns for V2X Interference Management
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Solution Overview
Problem
Existing methods for configuring demodulation reference signals (DM-RS) in vehicle-to-X (V2X) communication systems do not effectively manage DM-RS overhead and minimize interference between neighboring terminals.
Innovation Solution
The proposed solution involves generating and transmitting DM-RS signals using efficient group-hopping patterns, cyclic shifts, and orthogonal cover codes (OCCs) specifically designed for V2X communication, which allows for more symbols to be used in a subframe to account for high Doppler effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DM-RS overhead is increased to improve channel estimation accuracy, then measurement precision improves, but resource overhead increases
Solution Approach 1:
The patent applies parameter changes by modifying the group-hopping pattern parameters specifically for V2X communication. By changing the initialization parameters and hopping patterns of DM-RS sequences, the system achieves better channel estimation accuracy for high-mobility scenarios without simply increasing the number of DM-RS resources, thus resolving the contradiction between measurement precision and resource overhead.
2Reliability
If DM-RS sequences are configured for multiple symbols in a subframe to handle high Doppler effects, then reliability improves, but interference between neighbor terminals increases
Solution Approach 1:
The patent implements dynamics by introducing group-hopping patterns that dynamically change the DM-RS sequence across different symbols and slots. This dynamic variation ensures that neighboring terminals using the same time-frequency resources will have different DM-RS sequences at different times, reducing interference while maintaining reliable channel estimation for high-mobility V2X communication.
Solution Approach 2:
The patent applies periodic action through the group-hopping mechanism that periodically changes DM-RS sequences based on slot and symbol indices. This periodic variation in sequence generation creates time-varying separation between interfering signals from neighboring terminals, allowing reliable communication under high Doppler conditions while managing interference.
3Object-generated harmful factors
If group hopping is applied to minimize interference, then harmful factors reduce, but device complexity increases
Solution Approach 1:
The patent manages device complexity by changing parameters in a structured and standardized manner. The group-hopping pattern uses well-defined parameters (slot index, symbol index, terminal ID) to generate sequences, following existing 3GPP methodology. This approach reduces interference between DM-RS signals while keeping the implementation complexity manageable through parameter-based sequence generation rather than complex algorithms.
Data Source
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AI summary
A method performed by a user equipment, UE (300, 350) comprises determining, based on a first group-hopping pattern ∑i=07c16nssPSSCH+i⋅2imod30, a first group-hopping for a first symbol in a slot of a physical sidelink shared channel, PSSCH, determining, based on a second group-hopping pattern ∑(i=07c16nssPSSCH+8+i. 2i)mod30, a second group-hopping for a second symbol in the slot, transmitting, based on the first group-hopping for the first symbol in the slot, a first demodulation reference signal, DM-RS, for vehicle-to-everything, V2X, communication, and transmitting, based on the second group-hopping for the second symbol in the slot, a second DM-RS for V2X communication. In the first group-hopping pattern nssPSSCH is a number of the slot, c(x) denotes a pseudo-random sequence that is defined by a length-31 Gold sequence and initialized at the beginning of a slot of the PSSCH that satisfies nssPSSCH=0, and x=16nssPSSCH+i for the first symbol in the slot. In the second group-hopping pattern c(x) denotes the pseudo-random sequence, and x = 16nssPSSCH+8+i for the second symbol in the slot.