RLC PDU Payload Reduction for HSDPA Congestion Control
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Solution Overview
Problem
Current HSDPA networks face challenges in efficiently handling congestion over transport networks and radio links, as well as providing Quality of Service (QoS) differentiation within the same bearer, due to the reliable transmission protocols that prevent packet dropping or reordering, leading to increased round trip times and inefficient resource utilization.
Innovation Solution
A method is introduced where a radio access node determines and creates replacement RLC PDUs with smaller payloads to handle congestion and enable QoS differentiation by inserting or replacing RLC PDUs in the downlink data flow, allowing for efficient handling of lost packets and prioritization of data based on priority levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RLC AM protocol provides reliable transmission between RNC and UE, then packet loss is avoided and seamless handover is enabled, but round trip time increases significantly and congestion control becomes ineffective
Solution Approach 1:
The patent introduces an intermediary mechanism at the RNC level where a second RLC entity intercepts and manages retransmissions before they reach the UE. This intermediary RLC entity can discard duplicate packets and control retransmission behavior, thereby reducing RTT while maintaining reliability through controlled packet delivery.
Solution Approach 2:
The patent extracts the retransmission function from the end-to-end RLC AM path and relocates it to a local RNC-level RLC entity. By taking out the retransmission responsibility from the UE-side RLC, the system reduces round trip time while maintaining reliable delivery through the intermediary RNC-based retransmission mechanism.
2Reliability
If RLC protocol retransmits lost packets between RNC and UE, then non-congestion related packet loss is avoided, but TCP congestion control mechanism is not triggered and network capacity is inefficiently utilized
Solution Approach 1:
The RNC-level RLC entity acts as an intermediary that can distinguish between congestion-related losses and radio-related losses. By intercepting packets at the RNC, the system can trigger TCP congestion control for TN congestion while maintaining reliable delivery for radio losses, thereby improving network capacity utilization.
Solution Approach 2:
The patent applies different quality handling at different locations: the RNC-level RLC provides reliable delivery for radio link losses, while allowing packet drops to trigger TCP congestion control for transport network congestion. This local differentiation enables both reliability and efficient congestion control.
3Productivity
If all RLC PDUs are transmitted with full payload through Node B, then data throughput is maximized, but congestion over transport network or radio link cannot be efficiently handled and QoS differentiation is impossible
Solution Approach 1:
The patent introduces dynamic payload adjustment at the RNC level, where the second RLC entity can modify packet payloads or discard packets based on real-time congestion conditions and QoS requirements. This dynamic behavior enables adaptive throughput control while maintaining the ability to handle congestion and provide QoS differentiation.
Solution Approach 2:
The system changes the payload parameter of RLC PDUs dynamically at the RNC level. By modifying payload size or discarding packets based on congestion status and priority levels, the system achieves both efficient throughput utilization and adaptive congestion handling with QoS differentiation.
Data Source
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AI summary
The present invention relates to a technique of processing downlink data transmitted in a mobile communication system between a control node of a radio access network and a mobile terminal. A method embodiment of processing downlink data transmitted in a mobile communication system between a control node (100) of a radio access network and a mobile terminal (300) comprises: determining, in a radio access node (200) of the radio access network, at least one Radio Link Control, RLC, Protocol Data Unit, PDU, from a plurality of RLC PDUs transmitted by the control node (100), the determined at least one RLC PDU containing a payload; and creating, in the radio access node (200), at least one replacement RLC PDU to be further used instead of the determined at least one RLC PDU, wherein the at least one replacement RLC PDU contains a payload which size is smaller than the size of the payload of the determined at least one RLC PDU.