PRACH Transmission Beam Selection and Contention Resolution
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Solution Overview
Problem
Current 5G systems face challenges in efficiently managing the random access channel (RACH) procedure, particularly in selecting the optimal beams for transmission and ensuring reliable contention resolution.
Innovation Solution
The proposed method involves a user equipment (UE) transmitting a first message with randomly selected preambles using distinct beams, receiving a second message with control information, and then transmitting a third message with data using the same beams. This process includes measuring signal power and interference to determine the strongest beams for transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple random preambles are transmitted using distinct beams, then the reliability of RACH procedure is improved, but the device complexity increases
Solution Approach 1:
The UE performs beam measurement and identifies the N strongest beams before initiating the RACH procedure. This preliminary action ensures that when multiple preambles need to be transmitted, the UE already has a pre-determined set of optimal beams to use, reducing decision complexity during the actual RACH procedure while maintaining high reliability through diverse beam transmission
2Productivity
If beam measurement and selection is performed before RACH transmission, then the productivity of RACH procedure is improved, but the loss of time increases
Solution Approach 1:
Beam measurement and identification of N strongest beams is performed in advance during normal operation, so that when RACH transmission is needed, the UE can immediately proceed with multiple preamble transmissions using the pre-identified beams. This separates the measurement phase from the transmission phase, improving RACH productivity without permanently increasing time loss
3Measurement precision
If N strongest beams are determined based on signal power measurement, then the measurement precision is improved, but the object-affected harmful factors increase
Solution Approach 1:
The patent measures both signal power and interference power for each beam. By converting the harmful interference into a measurable parameter, the system can identify beams with high signal power relative to their interference levels. This approach transforms interference from a purely detrimental factor into useful information for beam selection, improving measurement precision while accounting for harmful effects
Data Source
AI summary
A method of random access channel (RACH) procedure performed at a user equipment (UE) includes certain steps. The method in one form includes transmitting a first message, including one or more random preambles selected from a set of preambles, to a base station (BS) employing distinct beams, receiving, from the BS, a second message including control information required for establishing communication between the UE and the BS indicating reception of at least one of the one or more of the selected random preambles, transmitting, to the BS, a third message employing the distinct beams used for the transmission of the first message at the BS, wherein the third message includes data required for establishing communications between the UE and the BS and receiving, from the BS, a fourth message that includes a contention resolution process confirming that the BS has correctly identified the UE.