Wireless Device Handover Delay Reduction via Stored DRS Data
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Solution Overview
Problem
In wireless communication systems operating in unlicensed spectrum, handover delays are prolonged due to uncertainties in downlink subframe availability caused by Listen-Before-Talk (LBT) failures, leading to service interruptions and increased latency, especially in congested network conditions.
Innovation Solution
A method where a wireless communication device performs a random access procedure for handover directly after receiving a handover command based on data associated with a discovery reference signal (DRS) subframe, without waiting for further periodically provided target cell DRS, using stored data validated by signal quality and age, to initiate the handover process within a configured or predetermined time frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the wireless communication device waits for periodically provided target cell DRS before performing random access procedure, then the handover can be executed with accurate frame timing information, but the handover delay increases due to LBT failures and DRS unavailability
Solution Approach 1:
The wireless communication device performs preliminary actions by storing DRS subframe data and validation criteria in advance during normal operation. When handover is needed, the device can immediately retrieve and validate stored data without waiting for new periodic DRS transmissions, thereby reducing handover delay while maintaining timing accuracy through pre-acquired information.
Solution Approach 2:
The patent introduces stored DRS subframe data as an intermediary element between the periodic DRS transmissions and the random access procedure. This intermediary allows the device to proceed with handover using cached information when new DRS is unavailable due to LBT failures, effectively bridging the gap between timing accuracy requirements and handover speed needs.
2Productivity
If the wireless communication device performs random access procedure immediately after receiving handover command without waiting for target cell DRS, then the handover delay is reduced, but the service interruption increases due to potential LBT failures
Solution Approach 1:
The device performs preliminary validation of stored DRS subframe data against predefined criteria before initiating the random access procedure. This preliminary action ensures that the cached data is still valid and suitable for handover, allowing immediate execution without waiting for new DRS while minimizing the risk of service interruption through data quality verification.
Solution Approach 2:
The patent implements a feedback mechanism where the device continuously monitors and validates the quality of stored DRS subframe data against predefined criteria. This feedback loop ensures that the device only proceeds with handover when the cached data meets quality thresholds, balancing rapid execution with reliable service by preventing premature handover due to poor data quality.
3Reliability
If the wireless communication device validates stored DRS data using multiple criteria including signal quality and age, then the handover reliability is improved, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by establishing specific validation criteria for stored DRS subframe data, including signal quality thresholds and age limitations. By defining concrete parameter ranges for validity assessment, the system achieves reliable handover selection without complex validation logic, as the criteria are straightforward comparisons against predefined values rather than complex algorithms.
Data Source
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AI summary
A method performed by a wireless communication device for reducing handover delay, wherein the wireless communication device is arranged to operate in a cellular communication system and to operate in a cell using unlicensed spectrum. The method comprises receiving a downlink, DL, signal from network node operating a neighbouring cell operating in the unlicensed spectrum, wherein the DL signal comprises a discovery reference signal, DRS, subframe holding data associated with the DRS subframe, receiving a handover command from a network node operating a serving cell where the neighbouring cell is a target cell, and performing a random access procedure for handover to the target cell. The performing of the random access procedure is performed directly after the reception of the handover command based on data associated with the DRS subframe without trying to receive the periodically provided target cell DRS. A device performing the method and a computer program for implementing the method are also disclosed.