PDCP Discard Reporting for XR Buffer Management
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Solution Overview
Problem
Extended Reality (XR) services in mobile networks face challenges in managing data bursts, which require timely scheduling and resource allocation to avoid delay and resource waste, especially due to the high data traffic and stringent delay budgets in 5G systems.
Innovation Solution
A method is introduced for a terminal in a mobile communication system to receive RRC messages with PDCP parameters, establish a Data Radio Bearer, and trigger a PDCP discard report when data units are discarded due to a timer expiry, including information on discarded SDUs to optimize resource management and scheduling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If uplink transmission is performed frequently to report buffer status and delay status for XR services, then scheduling timeliness and resource allocation accuracy are improved, but power consumption increases
Solution Approach 1:
The patent implements periodic discard timer mechanisms at both PDCP and RLC layers to periodically report discard status instead of continuous reporting. The PDCP discard timer (tDiscard) and RLC discard timer (tRLC-Discard) create periodic reporting intervals, allowing the system to balance scheduling timeliness with reduced power consumption by transmitting uplink control information only when discards occur or at periodic intervals rather than continuously
Solution Approach 2:
The system uses event-triggered reporting where discard status reports are automatically generated when specific conditions are met (SDU discard at PDCP layer, RLC PDU discard at RLC layer). This self-service mechanism eliminates the need for continuous network-configured reporting, allowing the terminal to autonomously determine when reporting is necessary based on actual discard events, thereby reducing unnecessary uplink transmissions and power consumption
2Loss of substance
If discard reporting is enabled for all SDUs, then resource waste is reduced through better scheduling, but device complexity increases
Solution Approach 1:
The patent applies discard reporting selectively at different protocol layers (PDCP and RLC) based on local conditions rather than uniformly across all data units. The PDCP layer reports discards for SDUs that meet specific criteria (e.g., tDiscard expiry), while the RLC layer independently reports discards for PDUs that meet its own criteria (e.g., tRLC-Discard expiry, max SDU discard count). This localized, condition-based reporting reduces overall reporting complexity compared to reporting all SDUs
3Reliability
If discard timer is started for each SDU, then delay budget compliance is improved, but processing overhead increases
Solution Approach 1:
The patent segments the discard monitoring function across multiple protocol layers (PDCP and RLC) rather than implementing a single centralized timer mechanism. Each layer maintains its own discard timer (tDiscard at PDCP, tRLC-Discard at RLC) and independently monitors its own data units. This segmentation distributes the processing overhead across layers, making the system more manageable while ensuring delay budget compliance at each layer for the specific SDUs/PDUs it handles
Data Source
AI summary
A method and apparatus for supporting XR services is provided. The method of a terminal includes receiving from a base station a Radio Resource Control (RRC) message, wherein the RRC message comprises a set of Packet Data Convergence Protocol (PDCP) parameters for a Data Radio Bearer (DRB), establishing a DRB based on the set of PDCP parameters, starting a discard timer for a Service Data Unit (SDU) of the DRB and triggering a PDCP discard report for the DRB in case that a parameter related to the PDCP discard report is comprised in the set of PDCP parameters for the DRB and one or more SDUs are discarded due to expiry of the discard timer and at least one SDU of the one or more SDUs has not been transmitted. The PDCP discard report comprises information on one or more discarded SDUs.