Logical Channel Prioritization Using PDCP Discard Timer Urgency
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Solution Overview
Problem
The priority-based token bucket algorithm in LTE systems does not adequately address the transmission requirements of delay-critical data, leading to potential delays in critical data transmission, especially for applications requiring low-latency communication like extended reality (XR), remote control, and teleoperation.
Innovation Solution
Introduce new logical channel parameters in the LogicalChannelConfig information element to prioritize resource allocation for logical channels with data having a remaining time of the PDCP discard timer less than a threshold, allowing these channels to be allocated resources even if they have a non-positive number of tokens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the priority-based token bucket algorithm is used for UL resource allocation, then PBR-based fairness is achieved, but delay-critical data transmission is not ensured when tokens are insufficient
Solution Approach 1:
The patent segments the resource allocation process into two distinct phases: first allocating resources to logical channels with sufficient tokens based on PBR, then separately allocating remaining resources to logical channels with delay-critical data. This segmentation allows the system to maintain PBR fairness for normal traffic while providing dedicated resource allocation for delay-critical data that would otherwise starve under the traditional token-based approach.
Solution Approach 2:
The patent performs preliminary identification of delay-critical data before resource allocation occurs. By checking the PDCP discard timer status in advance and marking logical channels with delay-critical data, the system prepares a priority list that ensures these channels receive resources first in the second allocation phase, preventing last-minute discards and ensuring timely transmission.
2Productivity
If resources are allocated strictly in decreasing priority order based on tokens, then PBR fairness is maintained, but logical channels with delay-critical data are starved when tokens are non-positive
Solution Approach 1:
The patent introduces dynamic adjustment to the static priority-based allocation by making the allocation process adaptive to real-time data urgency. Logical channels are dynamically re-prioritized based on PDCP discard timer status, allowing the system to flexibly switch between PBR-based allocation for normal traffic and urgency-based allocation for delay-critical data, thereby maintaining both efficiency and reliability.
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring PDCP discard timer status and using this information to adjust resource allocation decisions. The feedback loop ensures that when delay-critical data is detected (timer below threshold), the system responds by allocating resources to these logical channels even if their token buckets are empty, thus preventing data loss while maintaining overall system efficiency.
3Ease of operation
If logical channels without delay-critical data are served first in remaining resource allocation, then priority order is maintained, but in-time transmission of delay-critical data is not ensured
Solution Approach 1:
The patent segments the logical channel selection process into two groups: those with sufficient tokens and those with delay-critical data. This segmentation creates a clear two-phase allocation procedure that maintains simplicity by using straightforward priority-based selection in phase one, then urgent-need-based selection in phase two, avoiding complex real-time priority reordering while ensuring timely delivery of critical data.
Solution Approach 2:
The system performs preliminary classification of logical channels based on PDCP discard timer status before the allocation decision is made. By pre-identifying which channels contain delay-critical data and marking them accordingly, the system simplifies the allocation process by having a ready-made priority list that naturally prioritizes urgent data without requiring complex runtime calculations or dynamic priority adjustments during allocation.
Data Source
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AI summary
Various solutions for enhancements on token bucket algorithm in logical channel prioritization (LCP) are described. An apparatus may select a plurality of logical channels for an uplink (UL) grant. The apparatus may allocate resources of the UL grant to one or more of the plurality of logical channels in a decreasing priority order. Each of the one or more of the plurality of logical channels is associated with a positive number of tokens, or carries data with a remaining time of an associated packet data convergence protocol (PDCP) discard timer less than a threshold. Then, the apparatus may decrement the positive number of tokens by a total size of medium access control (MAC) service data units (SDUs) served to a corresponding logical channel of the one or more of the plurality of logical channels. After that, the apparatus may multiplex the MAC SDUs in a MAC protocol data unit (PDU) for transmission on the UL grant to a network node.