Secondary Cell Random Access Failure Control via Timer Deactivation
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Solution Overview
Problem
In LTE communication systems, there is no effective method to prevent infinite re-attempts of random access procedures on Secondary Cells (SCells), leading to potential network and user equipment overload, as there is no Radio Link Monitoring (RLM) for SCells, and declaring Radio Link Failure (RLF) on a PCell due to SCell failure is not a suitable solution.
Innovation Solution
A method where a base station initiates a random access procedure on an SCell and starts a timer; if the procedure is not completed before the timer expires, the base station sends a command to the user equipment to deactivate the SCell, thereby stopping the random access procedure and preventing infinite re-attempts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If random access procedure is continuously re-attempted on SCell, then connection reliability may be improved, but network and user equipment overload occurs
Solution Approach 1:
The base station proactively initiates a random access procedure on the SCell and starts a timer before actual data transmission is needed. This preliminary action allows the system to detect potential access failures early and deactivate the SCell beforehand, preventing the harmful effect of infinite re-attempts and subsequent overload while maintaining connection reliability.
Solution Approach 2:
The system implements a feedback mechanism where the base station monitors the completion status of the random access procedure on the SCell. If the procedure is not completed before the timer expires, the base station sends a deactivation command to the UE, creating a closed-loop control that prevents overload while ensuring reliable connection establishment.
2Reliability
If timer-based deactivation is implemented, then infinite re-attempts are prevented, but system complexity increases
Solution Approach 1:
The base station autonomously manages the random access procedure initiation and timer management without requiring complex external coordination. The system serves itself by automatically detecting timer expiration and sending deactivation commands, simplifying the overall system architecture while effectively preventing infinite re-attempts.
3Reliability
If SCell is deactivated upon timer expiry, then random access failures are stopped, but access speed is reduced
Solution Approach 1:
The timer is configured to expire after a reasonable duration that allows successful random access completion but prevents infinite re-attempts. This preliminary timing action balances the need to stop failures with maintaining acceptable access speed, deactivating the SCell only when necessary rather than immediately.
Data Source
AI summary
A method in a base station for controlling a Random Access, RA, procedure is provided. The base station initiates (201) an RA procedure on a Secondary Cell, SCell, in a User Equipment, UE, by sending to the UE a Physical Downlink Control Channel, PDCCH, order for a RA procedure on the SCell. At initiation of RA, the base station starts (202) a timer in the base station. The timer is a timer for random access failure detection associated with said initiated RA procedure. If the RA procedure has not been completed before expiry of said timer, the base station sends (205) a command to the UE, commanding the UE to deactivate the SCell, and thereby stopping the RA procedure on the SCell.