RACH-less Synchronized Handover via Time Advance Pre-calculation
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Solution Overview
Problem
Current wireless communication systems experience interruptions and inefficiencies during handovers due to the need for random access procedures, which cause delays and disruptions in data services as mobile devices transition from one base station to another.
Innovation Solution
A method for performing a synchronized and random access procedure-less handover, where user devices receive a handover command with a specified time to transition from a source base station to a target base station, allowing for seamless data transfer without interrupting services, by determining and using a time advance value to synchronize transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a random access procedure is used during handover, then the mobile device can obtain a time advance value with respect to the target base station, but the handover causes an interruption in data services for the mobile device
Solution Approach 1:
The target base station pre-calculates and provides the time advance value to the mobile device before the handover occurs. This is achieved by the target base station determining the time advance value based on its location and the mobile device's location, then including this value in the handover command message sent to the mobile device. This preliminary provision of the time advance value eliminates the need for post-handover random access procedures, thereby reducing handover interruption time while ensuring reliable time advance value acquisition
2Reliability
If a random access procedure is performed during handover, then the mobile device can synchronize with the target base station, but the handover process becomes more complex and time-consuming
Solution Approach 1:
The patent extracts the time advance value determination step from the random access procedure and performs it in advance by the target base station. Instead of requiring the mobile device to perform uplink transmissions and receive timing adjustments during handover, the system extracts only the essential synchronization parameter (time advance value) and provides it directly in the handover command. This simplifies the handover procedure by removing the random access exchange while maintaining synchronization reliability
Solution Approach 2:
The target base station performs preliminary synchronization preparation by calculating the time advance value before handover execution. This preliminary action includes determining the propagation delay between the target base station and the mobile device, then using this information to compute the appropriate time advance value that will be included in the handover command, thereby eliminating the need for post-handover synchronization procedures
3Reliability
If a random access procedure is used for handover, then the mobile device can establish connection with the target base station, but data transfer is interrupted during the transition
Solution Approach 1:
The system performs preliminary connection establishment preparation by providing the time advance value to the mobile device before handover execution. This allows the mobile device to immediately synchronize and begin data transfer with the target base station without interruption, as the connection parameters are already prepared and provided in advance through the handover command message
Data Source
AI summary
An example technique is provided for receiving, by a target base station (BS) from a source PS, information identifying a source cell or the source BS, and a first time advance value used by the user device to transmit signals to the source BS, receiving a signal by the target BS that was transmitted from the user device based on the first tune advance value, determining, by the target BS based upon the first time advance value and the received signal from the user device, a second time advance value to be used by the user device to transmit data to the target BS, sending the second time advance value from the target BS to the source BS, receiving, by the target BS, a handover of the user device from the source BS to the target BS, and receiving data by the target BS from the user device based on the second time advance value.