PRACH Format Dynamic Control for RRC Connection Failures
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Solution Overview
Problem
Wireless communication systems experience access blocks due to UEs being too far from the access node, leading to unsuccessful RRC-connection establishment, which causes delays and impacts user experience.
Innovation Solution
The access node dynamically adjusts the PRACH format based on the rate of access blocks to reduce the effective cell radius, allowing UEs to successfully connect by changing the cyclic-shift intervals, cyclic-prefix length, and guard period of random-access preamble transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the access node uses a larger effective cell radius to cover more UEs, then the coverage area is improved, but the likelihood of access blocks increases due to UEs being too far away
Solution Approach 1:
The patent applies dynamics by making the effective cell radius adjustable rather than fixed. The access node dynamically changes the PRACH format based on the observed rate of access blocks, allowing the effective cell radius to adapt to current network conditions. When access blocks are frequent, the effective cell radius is reduced; when access blocks are rare, it is increased, thus resolving the contradiction between coverage area and access success rate.
Solution Approach 2:
The patent changes physical parameters of the PRACH format (cyclic-prefix length, guard period, cyclic-shift intervals) to control the effective cell radius. By adjusting these parameters, the system can modify the maximum distance for successful random access preamble transmission, thereby controlling the effective cell radius to balance coverage area and access reliability.
2Reliability
If the access node reduces the effective cell radius to prevent access blocks, then the access establishment success rate is improved, but the coverage area decreases
Solution Approach 1:
The system dynamically adjusts the effective cell radius based on real-time monitoring of access block rates. Instead of using a permanently small radius that would limit coverage, the radius is expanded when conditions allow (low access block rates) and contracted when needed (high access block rates), thus maintaining both good coverage and high access success rates at different times.
Solution Approach 2:
The access node monitors the rate of access blocks as feedback and uses this information to adjust the PRACH format. This closed-loop feedback mechanism allows the system to respond to actual access conditions, expanding coverage when access is successful and reducing effective radius when access blocks occur, thereby resolving the contradiction between coverage area and access success rate.
3Device complexity
If the access node uses a fixed PRACH format, then the device complexity is reduced, but the adaptability to different access conditions deteriorates
Solution Approach 1:
The patent implements dynamics by transitioning from a fixed PRACH format to a dynamic one that can switch between different formats. The access node maintains multiple PRACH format configurations and selects the appropriate format based on the observed access block rate, thereby gaining adaptability while keeping the implementation manageable through predefined format options.
Solution Approach 2:
The access node autonomously monitors its own access block rate and self-adjusts the PRACH format without external intervention. This self-service capability allows the system to adapt to changing conditions automatically, improving versatility while maintaining relatively simple operation through automated decision-making based on predefined thresholds and formats.
Data Source
AI summary
A method and system for dynamically controlling random-access-request transmission in a cell provided by an access node, the access node supporting access attempts by user equipment devices (UEs). An example method includes (i) determining an extent to which the cell has experienced access blocks due to connection-request communication failure after successful random-access transmission and (ii) using the determined extent as a basis to dynamically set a physical random access channel (PRACH) format of the cell, wherein the PRACH format defines one or more configuration settings for random-access-request transmission by UEs in the cell and correlates with an effective radius of the cell.