Random Access Preamble Repetition for Cell-Edge Coverage Extension
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Solution Overview
Problem
Terminals located at the edge of a base station's coverage often experience degraded communication quality, leading to failed initial access procedures, necessitating improved methods for data transmission to enhance coverage.
Innovation Solution
A method for terminals to determine a repetition factor based on synchronization signal block measurements, allowing repeated transmission of random access preambles in specific RO groups, and a base station to configure threshold sets and RO groups for optimal preamble transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a terminal is located at the edge of coverage, then the coverage area is extended, but the communication quality is degraded
Solution Approach 1:
The patent implements periodic retransmission of the random access preamble multiple times at different power levels. The terminal transmits the preamble initially at a first power level, and upon not receiving a random access response, retransmits it at a second power level higher than the first. This periodic action with increasing power levels enables terminals at coverage edges to successfully establish connection despite degraded signal conditions.
2Reliability
If repeated transmission of random access preamble is performed, then the initial access success rate is improved, but the transmission time is increased
Solution Approach 1:
The patent dynamically adjusts the transmission power level based on the transmission attempt number. The terminal uses a first power level for the initial transmission and switches to a second power level for retransmissions. This dynamic power adjustment strategy improves the probability of successful access while managing the time loss by potentially reducing the number of retransmission attempts needed.
Solution Approach 2:
The terminal autonomously determines when to retransmit the random access preamble by monitoring for the absence of a random access response from the base station. The terminal self-manages the retransmission process by comparing timing expectations and automatically initiating power-adjusted retransmissions without requiring external control, thereby reducing overall access time.
3Area of stationary object
If the repetition factor is increased for coverage extension, then the coverage range is extended, but the power consumption is increased
Solution Approach 1:
The patent changes the power level parameter dynamically based on transmission attempts. Instead of continuously transmitting at maximum power, the terminal transmits at a lower first power level initially and only increases to a second power level when necessary for retransmissions. This parameter change strategy extends coverage to edge terminals while minimizing overall power consumption by avoiding unnecessary high-power transmissions.
Data Source
AI summary
A method of a terminal may comprise: receiving system information from a base station; identifying a threshold set including one or more threshold values from the system information; comparing a measurement result of a synchronization signal block (SSB) received from the base station with one threshold value of the threshold set; determining a repetition factor based on a result of comparison between the measurement result and the one threshold value; and repeatedly transmitting a random access (RA) preamble to the base station based on the repetition factor.