RLC Non-Persistent Mode Timer-Based Delay Control
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Solution Overview
Problem
Current radio access networks face challenges in maintaining Quality-of-Service (QoS) for delay-sensitive applications like Voice-over IP (VoIP) due to the reliance on sliding window-based approaches for RLC data block retransmissions, which can lead to excessive delay and frame errors, especially under varying radio conditions.
Innovation Solution
Implementing a timer-based packet buffering and retransmission approach that determines the validity of packet data based on a maximum data transfer delay constraint instead of a sliding window size, ensuring that RLC data blocks are deleted or retransmitted only within the specified delay limit, thus adhering to the QoS requirements of delay-sensitive applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sliding window-based approach is used for RLC data block retransmissions, then retransmission reliability is improved, but delay increases excessively for delay-sensitive applications
Solution Approach 1:
The patent implements dynamic adaptation of RLC mode selection based on radio conditions and application requirements. The system dynamically switches between acknowledged mode, non-persistent mode, and unacknowledged mode depending on the service type (delay-sensitive vs. delay-tolerant) and current channel quality, resolving the contradiction by making the retransmission mechanism adaptive rather than static
Solution Approach 2:
The patent changes key parameters including RLC mode selection, timer values (T310, N310), and maximum retransmission limits based on application QoS requirements. For delay-sensitive applications, the system adjusts parameters to limit retransmissions and enforce maximum delay constraints, thereby reducing delay while maintaining appropriate reliability levels
2Reliability
If RLC acknowledged mode is used with sliding window, then data integrity is improved, but complexity of the protocol increases
Solution Approach 1:
The patent applies different RLC mode configurations to different logical channels and application types. Instead of using a uniform acknowledged mode with sliding window across all services, the system applies acknowledged mode selectively to delay-tolerant applications while using simpler non-persistent or unacknowledged modes for delay-sensitive services, thereby reducing overall protocol complexity while maintaining data integrity where needed
Solution Approach 2:
The patent segments the RLC protocol operation into distinct modes (acknowledged, non-persistent, unacknowledged) that can be independently selected based on service requirements. This segmentation allows the system to use complex acknowledged mode only when necessary, while employing simpler modes for other traffic, thus reducing the effective complexity experienced by delay-sensitive applications
3Reliability
If retransmissions are performed without delay constraints, then reliability is improved, but QoS for delay-sensitive applications deteriorates
Solution Approach 1:
The patent implements feedback mechanisms through timers (T310, N310) that monitor transmission status and enforce maximum delay constraints. When the timer expires without successful delivery, the system receives feedback that the maximum delay has been exceeded and stops retransmissions, thereby preventing excessive delay while maintaining reliability within acceptable time bounds for delay-sensitive applications
Solution Approach 2:
The patent employs periodic timer-based checks (T310 timer with N310 counter) to enforce maximum transfer delay constraints. The system periodically evaluates whether the maximum delay has been exceeded and adjusts retransmission behavior accordingly, ensuring that reliability efforts do not exceed the QoS-defined delay budget for delay-sensitive applications
Data Source
AI summary
The transfer delay QoS attribute for delay-sensitive applications is enforced in radio access networks by determining the ongoing validity of incomplete data packets based on a maximum data transfer delay constraint. According to one embodiment, upper-layer packet data units (PDUs) associated with an application having a maximum data transfer delay constraint are transferred by starting a timer responsive to initial transmission of an RLC data block associated with one or more of the upper-layer PDUs. The timer is initialized to a timer value that is based on the maximum data transfer delay constraint. The RLC data block is retransmitted responsive to a received message indicating reception of the RLC data block is unacknowledged so long as the timer has not expired. The RLC data block is deleted from memory responsive to the timer expiring or a received message indicating reception of the RLC data block is acknowledged.