Multicast HARQ Retransmission Identification via Service ID
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Solution Overview
Problem
Current wireless communication systems face challenges in accurately handling hybrid automatic repeat request (HARQ) retransmissions for multicast services, leading to misunderstandings and errors due to the use of similar HARQ process IDs and data indicators across different transmission schemes, resulting in incorrect decoding and loss of data.
Innovation Solution
The proposed solution involves using specific combinations of radio network temporary identifiers (RNTIs) and service IDs to differentiate between initial and retransmitted transport blocks, ensuring that User Equipment (UE) correctly identifies and decodes retransmissions by employing UE-specific and group-common RNTIs, and incorporating service indices to distinguish between multicast and unicast services.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If group-common RNTI is used for scheduling multicast transmissions, then resource utilization is improved, but identification accuracy deteriorates due to ambiguity between initial and retransmitted blocks
Solution Approach 1:
The patent segments the identification mechanism by introducing service IDs that are specifically associated with multicast services. When a DCI schedules a transport block, the service ID is included to indicate multicast service context. This segmentation allows the system to maintain group-common RNTI for resource efficiency while adding a layer of service-specific identification that resolves ambiguity between initial and retransmitted blocks.
Solution Approach 2:
The patent introduces asymmetry in the identification approach by using different identification mechanisms for different service types. Unicast services use traditional RNTI-based identification, while multicast services use a combination of group-common RNTI plus service ID. This asymmetric approach allows optimized handling for each service type, maintaining resource efficiency for multicast while ensuring accurate identification through the additional service ID parameter.
2Device complexity
If HARQ process IDs are reused across different transmission schemes, then device complexity is reduced, but reliability deteriorates due to misunderstandings in retransmission identification
Solution Approach 1:
The patent introduces service ID as an intermediary element that mediates between the reused HARQ process ID and the actual transport block identification. When multiple transmission schemes use the same HARQ process ID, the service ID acts as a mediator that provides additional context to disambiguate whether a received block is an initial transmission or a retransmission, and which service it belongs to. This intermediary prevents misunderstandings while allowing HARQ process ID reuse.
Solution Approach 2:
The patent adds another dimension to the identification space by incorporating service ID alongside the traditional HARQ process ID. Instead of relying solely on the HARQ process ID (one-dimensional identification), the system now uses a two-dimensional identification approach combining HARQ process ID and service ID. This dimensional expansion allows reliable identification even when HARQ process IDs are reused across different transmission schemes.
3Measurement precision
If UE-specific RNTI is used for retransmissions, then identification accuracy is improved, but resource efficiency deteriorates due to increased signaling overhead
Solution Approach 1:
The patent makes the group-common RNTI multi-functional by enabling it to serve both initial multicast transmissions and retransmissions, unlike traditional approaches where different RNTIs are used for different purposes. By combining this universal RNTI usage with service ID inclusion in DCI, the system achieves both energy efficiency (through RNTI reuse) and accurate identification (through service ID). This multi-functionality reduces signaling overhead while maintaining identification accuracy.
Solution Approach 2:
The patent changes the parameters included in the DCI message to compensate for RNTI reuse. Instead of relying on RNTI to carry identification information, the system changes the DCI parameters by explicitly including service ID and other relevant information that enables accurate identification despite using the same group-common RNTI for multiple purposes. This parameter change approach reduces overhead compared to using UE-specific RNTIs while maintaining identification accuracy.
Data Source
AI summary
Embodiments of the present disclosure relate to HARQ retransmission for a multicast service. According to some embodiments of the disclosure, a method performed by a UE may include: receiving, from a BS, a first DCI for scheduling a first transmission using a HARQ process number, wherein a CRC of the first DCI is scrambled by a first RNTI; receiving, from the BS, a third DCI for scheduling a third transmission using the HARQ process number, wherein a CRC of the third DCI is scrambled by a third RNTI specific to the UE; and determining whether the third transmission is a retransmission of the first transmission or a retransmission of a second transmission scheduled by a second DCI, wherein the second DCI schedules the second transmission using the HARQ process number, a CRC of the second DCI is scrambled by a second RNTI common to a group of UEs including the UE.