HARQ Process Number Segmentation for 5G Multicast Reliability
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Solution Overview
Problem
In multicast/broadcast services for 5G New Radio (NR) systems, there is a challenge in ensuring reliable data retransmission to multiple user equipment (UEs) due to complexities in the Hybrid Automatic Repeat Request (HARQ) process, leading to potential data loss or misinterpretation by specific UEs.
Innovation Solution
A terminal and radio communication method that includes a reception unit for receiving a downlink data channel common to multiple terminals and a control unit that distinguishes between process numbers for automatic retransmission requests in group-common and terminal-specific channels, using specific identification information for scrambling channels during retransmission to ensure accurate data delivery to specific UEs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is retransmitted to a specific UE via unicast in MBS, then delivery reliability is improved, but the UE cannot properly receive the retransmitted data due to HARQ process ambiguity
Solution Approach 1:
The patent segments the HARQ process into two distinct parts: group-common HARQ processes for initial multicast transmission and UE-specific HARQ processes for unicast retransmission. This segmentation prevents confusion between different transmission types by assigning separate process number spaces, allowing UEs to properly identify and process retransmitted data without mixing up HARQ states between group and individual communications.
Solution Approach 2:
The patent introduces a mapping relationship as an intermediary between the group-common HARQ process number and the UE-specific HARQ process number. This mapping mechanism (stored in UE memory or configured via RRC signaling) acts as a bridge that allows the UE to translate the group-common HARQ process number received in multicast to the corresponding UE-specific HARQ process number for unicast retransmission, ensuring proper data reception without direct exposure to the ambiguity problem.
2Productivity
If the same HARQ process number is used for both group-common and UE-specific channels, then resource utilization is improved, but data loss or misinterpretation occurs at the UE
Solution Approach 1:
The patent segments the HARQ process number space into two independent domains: one for group-common channels and another for UE-specific channels. By maintaining separate process number assignments, the system avoids resource conflicts while ensuring that each channel type has its own dedicated identification space, preventing data misinterpretation at the UE side.
Solution Approach 2:
The patent applies local quality by allowing different HARQ process number assignment rules to apply locally to different channel types. Group-common channels use one set of process numbers optimized for multicast efficiency, while UE-specific channels use another set optimized for unicast reliability. This localized optimization resolves the contradiction between resource utilization and reception accuracy.
3Adaptability or versatility
If multiple HARQ handling methods are used for MBS retransmission, then flexibility in transmission strategies is improved, but UE cannot properly receive retransmitted data
Solution Approach 1:
The patent introduces a mapping relationship as an intermediary that simplifies UE operation while maintaining multiple HARQ handling methods. The mapping table (configured via RRC signaling or stored in UE memory) automatically translates between group-common and UE-specific HARQ process numbers, allowing the UE to handle multiple retransmission scenarios without complex manual configuration or decision-making, thus preserving ease of operation alongside flexibility.
Solution Approach 2:
The patent enables self-service by allowing the UE to automatically manage the mapping between group-common and UE-specific HARQ processes. The UE maintains its own mapping table and uses it to autonomously resolve HARQ process identification, eliminating the need for complex network control or manual intervention. This self-managing approach maintains flexibility in transmission strategies while keeping UE operation simple and automatic.
Data Source
AI summary
A terminal receives a downlink data channel common to a group of terminals in data distribution for multiple terminals. The terminal assumes that a process number of an automatic retransmission request in the downlink data channel is different from a process number of an automatic retransmission request in a terminal-specific downlink channel.