UE Cell Reselection for MBMS Service Continuity
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Solution Overview
Problem
User equipment (UE) in 3GPP LTE systems faces challenges in maintaining continuous multimedia broadcast multicast service (MBMS) reception due to limitations in supporting FeMBMS, which requires cell reselection to ensure uplink transmission capabilities, especially when receiving paging messages on MBSFN-dedicated frequencies that only allow downlink transmission.
Innovation Solution
The UE adjusts priority information to perform cell reselection, ensuring that frequencies supporting both downlink and uplink transmissions have higher priority, and establishes an RRC connection with a candidate cell that supports unicast transmission to maintain MBMS service continuity, including acquiring necessary system information directly from the candidate cell if configuration information is insufficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE camps on an MBSFN-dedicated frequency to receive MBMS service, then the MBMS service reception is enabled, but the UE cannot perform uplink transmission
Solution Approach 1:
The UE dynamically adjusts cell reselection behavior based on operational state. When in RRC idle state, the UE prioritizes camping on MBSFN-dedicated frequencies for MBMS reception. When uplink transmission is needed (e.g., receiving paging message), the UE triggers cell reselection to a frequency supporting uplink, demonstrating dynamic adaptation between different operational requirements
Solution Approach 2:
The UE changes the priority parameter of MBSFN-dedicated frequency based on service continuity needs. The network provides initial priority information, and the UE modifies this priority to ensure MBMS service continuity while allowing reselection to frequencies with uplink capability when necessary, effectively using parameter adjustment to resolve the contradiction
2Adaptability or versatility
If the UE performs cell reselection to a frequency supporting uplink transmission, then uplink transmission capability is enabled, but the MBMS service reception may be interrupted
Solution Approach 1:
The UE performs measurements and identifies candidate frequencies with uplink capability in advance while camping on MBSFN-dedicated frequency. When uplink transmission becomes necessary, the UE can quickly reselect to a pre-identified suitable frequency, minimizing service interruption. The network also provides priority information in advance to guide this process
3Ease of operation
If a UE not supporting FeMBMS excludes FeMBMS frequencies from MBMS interest frequencies, then the UE avoids camping on incompatible frequencies, but the MBMS service continuity cannot be maintained
Solution Approach 1:
The UE dynamically adjusts its frequency selection strategy based on service state. When MBMS service continuity is prioritized, the UE includes FeMBMS frequencies in its MBMS interest frequencies list despite not supporting FeMBMS. The UE then relies on priority information from the network and cell reselection mechanisms to ensure it camps on suitable frequencies, demonstrating dynamic adaptation of selection criteria
Solution Approach 2:
The network acts as an intermediary by providing priority information for different frequencies. The UE uses this priority information to guide its cell reselection process, allowing the network to control which frequencies the UE camps on, thereby ensuring service continuity even when the UE includes incompatible frequencies in its interest list
Data Source
AI summary
Provided are a method for performing cell reselection procedure in a wireless communication system and an apparatus supporting the same. A user equipment (UE) receives an information of a multicast-broadcast single-frequency network (MBSFN)-dedicated frequency; adjusts priority information on candidate frequencies such that the MBSFN-dedicated frequency has a lowest priority among the candidate frequencies on which the UE is allowed to camp; and performs cell reselection based on the adjusted priority information.