Access Control Mechanism for Wireless System Information Updates
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Solution Overview
Problem
In wireless communication systems like 3GPP UMTS LTE, system information changes can cause UEs to use outdated information during connection establishment, leading to failed RACH attempts and interference, especially when the modification period and RRC connection establishment overlap, resulting in wasted capacity and delays due to the need for UEs to wait until new system information is read before performing UL transmissions.
Innovation Solution
Introducing an 'Offset of Effective Period' and a 'New Access blocking offset' to allow UEs to continue previously started access procedures while preventing new access attempts until the new system information is effective, by transmitting new MIB and SIBs before the modification period and including a 1-bit SI-changing indication in the MIB to ensure UEs wait until the new SI is valid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UEs continue monitoring paging for SI change indication after origination, then they can detect system information changes, but they cannot perform UL transmissions during the SI reading period causing capacity waste and delays
Solution Approach 1:
The network performs preliminary actions by transmitting the SI change indication in the paging message before the UE needs to read the full system information. The UE is preemptively notified of the change and can immediately suspend access procedures without waiting to detect the change during normal paging monitoring, thus avoiding the blackout period while maintaining reliable change detection
Solution Approach 2:
The system dynamically adjusts the UE's access behavior based on the SI change status. When a change is indicated in the paging message, the UE transitions from normal access mode to a suspended state, and can resume immediately after the modification period without needing to wait for SI reading completion. This dynamic adaptation eliminates the capacity waste while ensuring UEs use updated system information
2Reliability
If UEs read new system information before performing RACH attempts, then they use valid system information, but this creates a blackout period of more than a second causing delays and capacity waste
Solution Approach 1:
The network transmits the SI change indication preliminarily in the paging message before the UE initiates or continues RACH procedures. This allows the UE to be aware of the change in advance and adjust its timing accordingly, reading the new system information just in time for the next valid RACH attempt without creating a prolonged blackout period
Solution Approach 2:
The system utilizes the periodic paging structure to deliver the SI change indication at predetermined intervals. By aligning the change notification with the periodic paging occasions, the UE can efficiently obtain the change information without continuous monitoring, and schedule its RACH attempts to coincide with periods when new system information is available, thus minimizing the blackout period while maintaining reliability
3Speed
If UEs send RACH attempts before modification period boundary, then they can establish connections faster, but they may use outdated system information leading to failed attempts and interference
Solution Approach 1:
The network provides feedback to the UE about system information changes through the paging message. When a change is detected, the UE receives explicit feedback indicating that new system information is available, and adjusts its RACH timing accordingly. This feedback mechanism ensures UEs send RACH attempts at the optimal time - after reading new system information but without creating unnecessary delays, thus maintaining both speed and reliability
Solution Approach 2:
The UE performs preliminary checking of the paging message for SI change indications before initiating RACH procedures. This preliminary action allows the UE to determine whether to proceed with immediate RACH attempts using current system information or to wait for the next modification period when new information is available, thereby avoiding failed attempts while minimizing connection establishment delays
Data Source
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AI summary
A method for preventing random access by a mobile station with outdated system information including receiving system information earlier than a time at which the system information is effective, determining that a current time is within a new access blocking offset before the time at which the system information is effective, and delaying random access at least until the time at which the system information is effective.