Inter-RAT Handover Multicast Service Continuity via Bearer Switching
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Solution Overview
Problem
During inter-radio access technology (inter-RAT) handover in wireless communication systems, multicast or broadcast (MB) services often experience interruptions or packet loss due to delays in configuring multicast radio bearers (MRBs) or switching to unicast dedicated radio bearers (DRBs).
Innovation Solution
A method where a user equipment (UE) receives system information identifying frequencies and MB services available via different radio access technologies (RATs), triggers a switch from a multicast radio bearer (MRB) to a unicast DRB before handover, and transmits an indication to the source base station about the MB service and frequency availability via the target base station, allowing for an MRB configuration to be received and applied after handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inter-RAT handover is performed without MB service continuity support, then handover procedure is simple, but MB service is interrupted and packet loss occurs
Solution Approach 1:
The UE triggers a switch from MRB to unicast DRB before handover occurs, preparing the alternative transmission path in advance. The UE also transmits an indication of MB service and frequency availability to the source base station prior to handover, enabling the network to prepare the target cell for MB service continuity. This preliminary action ensures that when handover happens, the MB service can be maintained without interruption.
Solution Approach 2:
The UE transmits an indication to the source base station about MB service and frequency availability via the target base station. This feedback mechanism allows the network to be aware of the UE's MB service requirements and the availability of suitable frequencies at the target cell, enabling coordinated preparation for seamless handover.
2Loss of time
If the UE waits for MRB configuration after handover, then handover execution is simple, but MB service continuity is lost due to delays
Solution Approach 1:
The UE switches from MRB to unicast DRB before handover and transmits the MB service indication to the source base station in advance. This preliminary preparation eliminates the need to wait for MRB configuration after handover, as the alternative transmission path is already established and the network is prepared for the transition.
3Reliability
If the UE switches to unicast DRB before handover, then MB service continuity is maintained, but additional signaling and configuration are required
Solution Approach 1:
The UE triggers the switch from MRB to unicast DRB before handover occurs, preparing the alternative transmission path in advance. This preliminary action reduces the complexity during the actual handover execution, as the bearer switching is completed before the handover event rather than during it.
Solution Approach 2:
The unicast DRB acts as an intermediary transmission path between the MRB and the target cell. By switching to this intermediary bearer before handover, the UE ensures continuous MB service reception while the network prepares for the final transition to the target cell's MRB.
4Reliability
If MB service indication is transmitted to source base station, then target cell can be properly configured, but additional signaling messages are required
Solution Approach 1:
The UE transmits an indication to the source base station about MB service and frequency availability. This feedback message contains crucial information about the UE's MB service requirements and the availability of suitable frequencies at the target cell, enabling the network to accurately configure the target cell for seamless handover.
Solution Approach 2:
The indication message serves multiple functions: it notifies the source base station of the UE's MB service requirements, provides frequency availability information for the target cell, and triggers the necessary network preparations for handover. This multi-functionality reduces the need for separate signaling messages.
Data Source
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AI summary
In some aspects, a user equipment (UE) may receive, via a first radio access technology (RAT), system information that identifies a set of frequencies of a second RAT and one or more available multicast or broadcast (MB) services. The UE may trigger a switch from a first multicast radio bearer (MRB), of the first RAT, to a first unicast dedicated radio bearer (DRB), of the first RAT, for reception of an MB service via the first RAT. The UE may transmit an indication that indicates the MB service or a frequency via which the MB service is available via the second RAT. The UE may receive an MRB configuration associated with receiving the MB service via a target base station using the second RAT. The UE may switch from a second unicast DRB, of the second RAT, to a second MRB, of the second RAT, after handover.