Multi-pilot Reference Signals for Grant-free Collision Reduction
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Solution Overview
Problem
In wireless communication systems, especially in grant-free transmissions, the high probability of preamble collisions among users leads to increased overhead and detection complexity, reducing the efficiency of data demodulation and increasing the difficulty of implementation as the number of users grows, due to the need for larger preamble pools which occupy more time-frequency resources and reduce payload capacity.
Innovation Solution
The use of uncorrelated and independently generated pilot sequences, selected from multiple predetermined pools, including PRACH preamble and DMRS sequence pools of LTE and NR standards, reduces the likelihood of collisions by allowing each user to autonomously select unique preamble sequences, thereby reducing the complexity of blind detection and improving spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional single-pilot schemes are used, then implementation complexity is low, but collision probability increases and detection reliability deteriorates as user count grows
Solution Approach 1:
The patent divides the single pilot signal into multiple uncorrelated pilot sequences (W≥2) that are independently generated or selected. Each pilot sequence can be independently detected, which segments the detection process and improves reliability through diversity while maintaining manageable complexity through standardized generation methods
Solution Approach 2:
The patent changes the parameter of pilot sequence correlation from correlated (traditional) to uncorrelated. By using uncorrelated sequences generated through different methods (different Zadoff-Chu roots, different cyclic shifts, different scrambling sequences), the system improves detection reliability under high user loads while the generation methods remain within existing standard frameworks
2Reliability
If larger preamble pools are used to reduce collisions, then collision probability decreases, but time-frequency resource occupation increases and payload capacity is reduced
Solution Approach 1:
The patent segments the collision avoidance function across multiple pilot sequences rather than relying on a single large pool. Each user transmits W uncorrelated sequences, and the receiver can detect any of them, effectively distributing the collision resistance across multiple smaller sequence sets rather than requiring one large pool
Solution Approach 2:
The patent adds the dimension of sequence uncorrelation and independent selection. Instead of expanding the pool size in one dimension, it creates multiple independent detection paths through uncorrelated sequences, effectively increasing the detection space without proportionally increasing resource occupation
3Measurement precision
If multiple uncorrelated pilot sequences are used, then demodulation performance improves, but signal processing complexity increases
Solution Approach 1:
The patent segments the channel estimation and demodulation process into W independent parallel paths, each processing one uncorrelated pilot sequence. This segmentation allows for independent estimation that can be combined, improving precision while keeping each processing path manageable through standardized operations
Solution Approach 2:
The patent merges the results from W independent pilot sequence detections through combining operations at the receiver. By coherently or non-coherently combining the detection results from multiple uncorrelated sequences, the system achieves improved demodulation performance while the processing complexity is distributed and managed through systematic combining algorithms
Data Source
AI summary
Disclosed are methods, apparatuses, systems, and computer readable media. In one aspect, a wireless communication method is disclosed. The method includes generating, at a first radio terminal, a signal comprising a pilot signal, wherein the pilot signal includes W pilot sequences, wherein W is an integer, and wherein the W pilot sequences are uncorrelated; and transmitting, from the first radio terminal to a second radio terminal, the signal.