RACH-Less Handover Beam Selection Without PRACH
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Solution Overview
Problem
In wireless communication systems, RACH-less handover procedures face challenges in determining the transmitter/receiver (Tx/Rx) beam for user equipment (UE) due to the absence of a physical random access channel (PRACH) operation, which hinders efficient handover in 3GPP 5G NR networks.
Innovation Solution
The UE receives an uplink grant and an identifier of a reference signal from the source node, measures multiple beams of the target node, generates a measurement report, and selects an appropriate uplink grant based on signal quality to establish a connection, with the option to fallback to PRACH-based handover if necessary, enabling efficient beam selection during RACH-less handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If RACH-less handover procedure is used to reduce handover interruption time, then handover speed is improved, but beam determination becomes difficult due to absence of PRACH operation
Solution Approach 1:
The network node provides the UE with an identifier of a reference signal associated with a beam of the target node before the handover is performed. This preliminary provision of beam information enables the UE to perform RACH-less handover without needing to perform PRACH operations for beam determination, thus reducing handover interruption time while maintaining beam determination capability
Solution Approach 2:
A reference signal identifier acts as an intermediary that carries beam information from the network to the UE. Instead of requiring direct PRACH operations for beam determination, the reference signal identifier mediates the beam selection process by providing the UE with pre-determined beam information, enabling efficient RACH-less handover
2Reliability
If multiple beams are measured and uplink grant selection is performed to ensure reliable connection establishment, then connection reliability is improved, but handover procedure complexity increases
Solution Approach 1:
The patent changes the parameter of beam information representation by providing a reference signal identifier instead of requiring full beam measurement and reporting procedures. This parameter change simplifies the handover procedure while maintaining connection reliability, as the network can select the most appropriate beam based on pre-performed measurements and provide the corresponding identifier to the UE
Data Source
AI summary
This disclosure describes methods, systems, and devices for handover of a user equipment (UE) from a source node of a radio access network (RAN) to a target node of the RAN. In one example, a method involves receiving, by the UE and from the source node, a RACH-498 handover message comprising: (i) an uplink grant for establishing a connection with the target node, and (ii) an identifier of a reference signal associated with a beam of the target node. The method also involves performing, by the UE, a handover based on the RACH-less handover message.