DRX Timing Synchronization Recovery in LTE Active State
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Solution Overview
Problem
In LTE networks, DRX timing de-synchronization between the eNB and UE in the LTE_ACTIVE state leads to increased downlink message delivery latency and wastage of radio resources, as the eNB misinterprets discontinuous transmission (DTX) feedback, causing loss of MAC-PDUs and inefficiencies in resource management.
Innovation Solution
The solution involves detecting DRX timing de-synchronization and employing methods such as broadcasting the UE's RNTI in system information for continuous reception notification or pre-configuring an absolute wake-up time to synchronize the UE's DRX, ensuring timely data transmission and recovery from synchronization losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the UE automatically increments DRX length according to a rule, then the UE can save battery resources by extending idle periods, but the eNB and UE become desynchronized in DRX timing
Solution Approach 1:
The patent applies preliminary action by having the eNB pre-configure an absolute wake-up time for the UE before DRX operation begins. This absolute wake-up time serves as a reference point that both the eNB and UE use to synchronize their DRX cycles. By establishing this synchronization baseline in advance, the system prevents timing drift that would otherwise occur when the UE independently increments its DRX length, thus maintaining reliability while still allowing battery savings through DRX operation.
2Productivity
If the eNB maintains current DRX value while UE increments its own DRX value, then the UE can operate independently to save energy, but downlink message delivery latency increases
Solution Approach 1:
The patent implements feedback mechanisms where the eNB monitors whether the UE is awake or asleep during expected DRX wake periods. When the eNB detects that the UE is asleep (through lack of acknowledgment or specific feedback signals), it can trigger a wake-up signal to immediately awaken the UE. This feedback loop allows the system to maintain independent DRX operation for energy savings while providing a corrective mechanism to reduce latency when downlink messages need urgent delivery.
3Reliability
If the eNB sends probing messages to recover DRX synchronization, then the UE can be awakened to regain synchronization, but radio resources are wasted
Solution Approach 1:
The patent applies preliminary action by pre-configuring the absolute wake-up time that serves as a common reference for both eNB and UE. This prevents the need for probing messages in the first place, as both parties already know when the UE should be awake. By establishing synchronization in advance through pre-configured timing information, the system avoids the resource-wasting probing and wake-up signal exchanges that would otherwise be necessary to recover from desynchronization.
Data Source
AI summary
A method for recovering from discontinuous reception (DRX) timing de-synchronization between the UE and the eNB in an LTE_ACTIVE state having the steps of: the eNB detecting DRX timing de-synchronization; transmitting an indicator to a User Equipment (UE) to resume continuous reception; and waiting for an indication from the UE of whether a Continuous Reception Response or Continuous Reception Notification was received.