Multi-Flow HSDPA Congestion Control via Link Segmentation
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Solution Overview
Problem
Current congestion control methods in high-speed downlink packet access (HSDPA) systems, such as active queue management based congestion control (ABCC), fail to fully utilize the aggregated capacity of multiple links during multi-point transmission, leading to inefficient data flow and packet loss due to TCP congestion mechanisms being triggered by link congestion.
Innovation Solution
The method involves distributing data units between primary and secondary communication links based on calculated weights, where ABCC is only applied to the primary link, and the secondary link is not informed of congestion, allowing for TCP-compatible congestion control without packet loss on the secondary link, thereby optimizing data flow across multiple links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ABCC is applied to multiple links in multi-point HSDPA transmission, then congestion control is provided for all links, but TCP congestion avoidance mechanisms are triggered causing packet loss and preventing full utilization of aggregated capacity
Solution Approach 1:
The patent segments the multi-link transmission system into primary and secondary links with different congestion control treatments. The primary link receives full ABCC congestion control while secondary links are excluded from ABCC, allowing them to maintain higher data rates without triggering TCP congestion mechanisms, thus resolving the contradiction between reliable congestion control and maximum throughput.
Solution Approach 2:
Different congestion control qualities are applied to different links based on their roles. The primary link gets aggressive ABCC congestion control for reliability, while secondary links get lenient or no ABCC to maintain high throughput. This local differentiation allows the system to achieve both reliable congestion control where needed and maximum productivity where possible.
2Quantity of substance
If ABCC is used for congestion control on all links, then buffer management is improved, but end-user IP packets are destroyed triggering TCP retransmission and reducing effective data flow
Solution Approach 1:
The patent segments the buffer management approach by applying ABCC buffer control only to the primary link while excluding secondary links from ABCC buffer management. This allows the system to maintain buffer capacity utilization through ABCC on the primary link while avoiding packet destruction on secondary links, thereby preventing TCP retransmission triggers and reducing overall packet loss.
Solution Approach 2:
The primary link acts as an intermediary that absorbs the aggressive ABCC buffer management, protecting the secondary links from packet loss. By concentrating ABCC buffer control on the primary link, the system maintains buffer management benefits while the secondary links continue to deliver data without triggering TCP congestion mechanisms.
3Ease of operation
If data is transmitted over multiple links with equal weighting, then link utilization is balanced, but the system cannot adapt to dynamic congestion conditions on individual links
Solution Approach 1:
The patent implements dynamic weight adjustment for multi-link transmission based on real-time congestion detection. When congestion is detected on a link, the system dynamically adjusts the weight distribution to favor non-congested links. This dynamic adaptation allows the system to maintain both load balancing under normal conditions and congestion adaptation when needed, resolving the contradiction between operational simplicity and adaptability.
Solution Approach 2:
The system uses feedback from congestion detection mechanisms to adjust transmission weights on different links. When congestion is detected on a primary link, the feedback triggers a reconfiguration that shifts more traffic to secondary links. This feedback-driven weight adjustment enables the system to adapt to dynamic congestion conditions while maintaining ease of operation through automated control.
Data Source
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AI summary
In a multi flow HSDPA system comprising a RNC (402) and a plurality of NodeB's (404, 406), the present disclosure includes (re-) use of original active queue management, AQM, based congestion control, ABCC for a primary link (421). For every detected congestion, an end-user IP packet is destroyed. ABCC is not used for the secondary link (422), which means that application level TCP will not be informed about congestion on the secondary link (422). The radio link control, RLC, protocol data units, PDU, (432) are distributed among links based on the congestion status of the links. If secondary link (422) is congested then more packets will be transmitted on the primary link (421). This makes it possible to use TCP compatible congestion control for multi flow HSDPA, without the drawback that would result from TCP reacting unnecessarily on flow bitrate decrease.