RACH Triggering via Buffer Status Changes in LTE
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Solution Overview
Problem
In telecommunications systems, particularly in LTE access technology, the contention-based Random Access Channel (RACH) procedure experiences performance degradation due to increased collisions as the number of users in RRC_CONNECTED state grows, leading to high load on control channels and potential delays in prioritizing high-priority data, especially when users are non-synchronized or lack uplink scheduling request resources.
Innovation Solution
A method where a mobile terminal initiates a RACH procedure based on specific buffer status changes, such as the arrival of higher-priority data, a buffer size increase exceeding a threshold, or a specified time since the last RACH initiation, allowing the base station to quickly identify and allocate resources to prioritized data without unnecessary channel load or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of users in RRC_CONNECTED state is increased to support more simultaneous sessions, then the network capacity and coverage are improved, but the collision probability on RACH channel increases and performance degrades
Solution Approach 1:
The patent implements dynamic RACH resource allocation where the base station scheduler dynamically assigns dedicated RACH resources to specific users based on their buffer status and data priority. This dynamic approach allows the system to support more users simultaneously while maintaining reliable RACH procedures by eliminating collisions through user-specific resource allocation.
2Speed
If RACH procedures are frequently initiated to ensure timely data transmission, then the data transmission timeliness is improved, but the control channel load increases and power consumption rises
Solution Approach 1:
The patent changes the triggering parameters for RACH initiation from time-based or event-based to buffer-status-based. The mobile terminal monitors its buffer status and only initiates RACH procedures when specific buffer status conditions are met (e.g., buffer size exceeds threshold, high-priority data arrives). This parameter change reduces unnecessary RACH transmissions while ensuring timely transmission when actually needed, thereby reducing power consumption and control channel load.
3Speed
If the base station monitors all users in RRC_CONNECTED state for scheduling opportunities, then the scheduling responsiveness is improved, but the processing complexity and resource requirements increase
Solution Approach 1:
The patent extracts and monitors only the buffer status information that is critical for scheduling decisions, rather than monitoring all possible user parameters. The base station receives buffer status reports from users and focuses scheduling attention on users with significant buffer status changes or high-priority data, thereby reducing processing complexity while maintaining scheduling responsiveness.
4Productivity
If dedicated scheduling request resources are allocated to maintain UL synchronization, then the uplink scheduling efficiency is improved, but the number of users that can be supported in session active state decreases
Solution Approach 1:
The patent makes the RACH channel serve multiple functions: it is used both for initial access and for buffer status reporting by users in RRC_CONNECTED state. By this multi-functional use, dedicated scheduling request resources are freed up, allowing more users to be supported in session active state while maintaining uplink scheduling efficiency through the universal RACH mechanism.
Data Source
AI summary
The present invention relates to a method and arrangement for triggering a Random Access Channel (RACH) procedure for requesting uplink resources on a random access channel to a radio base station (600) scheduler based on a change in terminal (700) buffer status as compared to a Buffer Status Report BSR stored in said terminal. In a first method step, the status of the present terminal buffer content, i.e. terminal buffer data, is compared with the status of said stored buffer status report BSR. A second method step involves initiating a RACH procedure for indicating a service request to said base station scheduler upon detecting a change of buffer status at said comparison. The service request includes an indicator of the status change as a trigger for said scheduler to assign uplink resources to said terminal.