Timing Advance Mechanism for RACH-less Handover in IAB Networks
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Solution Overview
Problem
In wireless communication networks, especially those using millimeter wave frequencies, handover processes in integrated access and backhaul networks face challenges such as service interruptions due to sudden radio signal deterioration or blockages, which are not effectively addressed by conventional mobility-based handover techniques, leading to quality of service issues for multiple users.
Innovation Solution
The implementation of a timing advance (TA) mechanism that allows for RACH-less handovers by measuring timing differences between nodes and adjusting transmission times, enabling seamless handovers without the need for random-access channel procedures, thereby minimizing service interruptions and optimizing network topology adaptations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional mobility-based handover techniques are used, then handover procedures can be executed with standard protocols, but service interruptions occur due to radio signal deterioration and blockages in millimeter wave networks
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing timing advance values for multiple target cells before handover is needed. When handover occurs, the UE can immediately use the pre-computed TA value without waiting for random access procedures, thus eliminating service interruptions and reducing handover execution time in millimeter wave networks
2Measurement precision
If random-access channel procedures are used for handover, then timing synchronization can be established, but handover execution time increases and service disruptions occur
Solution Approach 1:
The patent performs timing advance calculation in advance during the handover preparation phase. The source base station computes the TA value based on uplink timing measurements and includes it in the handover command, allowing the UE to achieve timing synchronization immediately upon handover without executing random-access procedures
Solution Approach 2:
The patent extracts the timing synchronization function from the random-access procedure by separately computing and providing the timing advance value through higher-layer signaling. This separates the timing alignment task from the random access protocol, eliminating the need for message exchange while maintaining synchronization accuracy
3Productivity
If RACH-less handover with pre-computed TA values is implemented, then handover execution time is reduced and service interruptions are minimized, but additional signaling overhead is required to provide TA values to UEs
Solution Approach 1:
The patent uses the existing handover command message structure to carry timing advance values, making the signaling mechanism multi-functional. The same RRC reconfiguration message that directs handover also provides the TA value, eliminating the need for separate signaling and reducing overall overhead while enabling fast handover
Data Source
AI summary
A technique of performing a handover procedure involves providing a proper timing adjustment indication for the UE performing RACH-less HO. Even though the discussion herein is on IAB scenarios and the idea takes an advantage of IAB nodes being in fixed locations (i.e., not moving in the network), it can be applied to UEs in general. The timing adjustment provided in performing a HO in an IAB network according to the improved techniques involves computing a timing advance (TA) to be used by an IAB node prior to executing HO to an alternative serving node. Such a use of a TA may enable a bypassing of a RACH procedure when accessing a cell.