SRAP Control PDUs for QoS and Feedback in UE Relay Links
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Solution Overview
Problem
The introduction of Layer 2 UE-to-UE (U2U) relay in NR Release 18 requires further specification of the sidelink relay adaptation protocol (SRAP) sublayer, particularly for handling bearer quality of service (QoS), next hop feedback, delay measurement, and packet discard status, which are not adequately addressed in existing technologies.
Innovation Solution
The implementation of SRAP control PDUs for bearer QoS control, next hop feedback control, delay measurement, and packet discard status within the SRAP layer to enhance QoS handling, scheduling adjustments, and traffic prioritization between remote UEs in the L2 U2U relay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If L2 UE-to-UE relay operation is established with multiple remote UEs, then relay assistance and extended coverage are achieved, but protocol complexity and signaling overhead increase
Solution Approach 1:
The patent segments the relay operation into distinct phases (setup phase with path selection messages, data transfer phase, and teardown phase) and defines specific PDU types for each phase. This segmentation allows the protocol to manage complexity by handling different aspects of relay operation separately rather than requiring a single complex protocol mechanism.
Solution Approach 2:
The relay UE acts as an intermediary between source and target remote UEs, forwarding data and control messages. The patent defines specific message formats for this intermediary function, including path selection requests/responses and data forwarding PDUs, which simplify the interaction between end devices while enabling extended communication ranges.
2Productivity
If SRAP control PDUs are implemented for QoS control and feedback, then QoS management and scheduling efficiency are improved, but signaling overhead and processing complexity increase
Solution Approach 1:
The patent merges multiple control functions into the SRAP control PDU structure, which can carry path selection information, QoS parameters, and feedback messages in a unified format. This reduces the number of separate signaling messages needed while maintaining comprehensive control capabilities for relay operations.
Solution Approach 2:
The patent implements feedback mechanisms where the relay UE and remote UEs exchange status information, QoS metrics, and path quality measurements through control PDUs. This feedback enables dynamic scheduling adjustments and QoS optimization without requiring continuous high-level signaling, as the feedback is embedded in the existing data plane messages.
3Reliability
If real-time feedback mechanisms are implemented for delay measurement and packet discard status, then communication reliability is improved, but processing overhead and latency increase
Solution Approach 1:
The patent establishes path selection and QoS parameter configuration in advance during the setup phase, before actual data transfer begins. This preliminary configuration reduces the need for real-time decision-making during data transmission, thereby minimizing processing overhead and latency while maintaining reliability through pre-optimized paths.
Solution Approach 2:
The patent implements continuous monitoring and feedback mechanisms where delay measurements and packet discard status are tracked ongoing through the data transfer process. This continuous action allows for dynamic adjustments without interrupting the data flow, maintaining reliability while minimizing the impact of feedback processing on overall transmission latency.
Data Source
AI summary
A user equipment (UE) establishing a layer 2 (L2) UE-to-UE (U2U) relay operation, wherein the source remote UE and the relay UE communicate via a first sidelink (SL) and wherein the relay UE and the target remote UE communicate via a second SL. The UE generates a SL relay adaptation protocol (SRAP) protocol data unit (PDU) including a SRAP header comprising an identifier for at least the target remote UE or the source remote UE, wherein the SRAP header indicates a request, provides a measurement or provides a status with respect to the first or second SL.