RACH Signal Phase Pattern Vector Selection for mmWave Random Access
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Solution Overview
Problem
In mmWave wireless communication systems, the high pathloss and potential RACH signal collisions between user equipment and base stations pose challenges for establishing a stable random access procedure, particularly in areas with radio shadows and multiple user equipment connections.
Innovation Solution
A method is introduced that involves selecting a phase pattern vector from a set for repetitive transmission of RACH signals, using orthogonal or quasi-orthogonal sequences, and determining the repetitive transmission count based on pathloss to minimize signal collisions and complexity, while maintaining backward compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repetitive transmission of RACH signal is increased to overcome pathloss in mmWave band, then connection stability is improved, but device complexity and signaling overhead increase
Solution Approach 1:
The patent changes the parameter of phase pattern vectors applied to RACH signals. By selecting different phase pattern vectors from a predefined set based on transmission count, the system achieves diverse signal characteristics for repetitive transmissions without increasing complexity. The phase pattern vectors are mathematical transformations (e.g., Hadamard, DFT) that modify the signal phase in a structured way, allowing the base station to distinguish between different repetitive transmissions while maintaining manageable device complexity.
2Productivity
If multiple user equipments transmit RACH signals simultaneously, then access efficiency is improved, but signal collision between user equipments occurs
Solution Approach 1:
The patent segments the RACH signal space by introducing phase pattern vectors as an additional dimension. Instead of relying solely on time-division or frequency-division multiplexing, the system divides the signal space using orthogonal or quasi-orthogonal phase patterns. This allows multiple user equipments to transmit simultaneously on the same time-frequency resources while maintaining distinguishable signals through their unique phase patterns, thereby improving access efficiency while reducing collisions.
Solution Approach 2:
The patent adds a phase dimension to the RACH signal structure. By multiplying RACH signals with phase pattern vectors from sets such as Hadamard or DFT matrices, the system creates signals that differ in phase characteristics rather than just time or frequency. This dimensional expansion allows multiple UEs to share the same time-frequency resources without collision, as the base station can separate signals based on their phase patterns through correlation detection.
3Reliability
If phase pattern vector set is expanded to resolve RACH signal collision, then collision resistance is improved, but device complexity and processing load increase
Solution Approach 1:
The patent employs universal mathematical transforms (Hadamard, DFT) that serve multiple functions. These transforms provide orthogonal or quasi-orthogonal phase patterns that inherently offer collision resistance, while also enabling efficient signal processing through well-established algorithms. The same mathematical framework supports both the generation of diverse phase patterns for collision avoidance and the detection/separation of multiple signals at the base station, reducing overall processing complexity despite the expanded signal space.
Data Source
AI summary
Disclosed are a method for performing a random access and a terminal, the method comprising: acquiring information on a sequence set and information on a phase pattern vector set to be used during a random access step; selecting, from among a plurality of phase pattern vectors included in the phase pattern vector set, any one phase pattern vector corresponding to the repeating transmission frequency of an RACH signal; transmitting, to a base station, the generated RACH signal for a time period up to the repeating transmission frequency by using the selected phase pattern vector and any one sequence selected from among a plurality of sequences included in the sequence set; and receiving, from the base station, an RACH response signal indicating an estimated sequence and an estimated phase pattern vector.