Flow Control Using On-Off Signals in High Delay Networks
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Solution Overview
Problem
Wireless networks face buffer overflows and packet losses due to the lack of sophisticated flow control mechanisms, leading to inefficient queue management and large buffer sizes, which are undesirable for responsive network conditions.
Innovation Solution
Implementing a method that uses time-separated ON-OFF signaling to control traffic flows, approximating credit-based flow control by transmitting FlowON and FlowOFF messages based on link delay to manage per-flow queues efficiently, allowing for smaller buffer sizes and improved responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ON-OFF flow control is used with high bandwidth delay product networks, then buffer size Q must be increased to account for link delay D, but this leads to large queue sizing which is undesirable in the BS
Solution Approach 1:
The patent applies preliminary action by having the BS send FlowON messages to the PGW in advance, allowing the PGW to pre-fetch packets before they are needed at the BS. This anticipatory approach compensates for link delay without requiring large buffers at the BS, as packets arrive just in time for transmission to users.
Solution Approach 2:
The patent implements feedback through the FlowON/FlowOFF message exchange between BS and PGW. The BS monitors its queue status and sends FlowON messages when buffer space is available, and FlowOFF messages when the queue is full. This closed-loop feedback mechanism allows dynamic adaptation to link delay conditions while maintaining small buffer sizes.
2Reliability
If a large per-flow queue is implemented to account for link delay, then buffer overflow is prevented, but the packets in the queue have to be coded in a way that responds to network conditions and a large buffer makes it non-conducive to change the packets mid-stream
Solution Approach 1:
By having the PGW pre-fetch packets in advance using FlowON messages, the system prepares packets ahead of time at the PGW where coding adaptation can occur. This allows network condition responses to be implemented at the PGW rather than requiring large buffers at the BS, maintaining both reliability and adaptability.
Solution Approach 2:
The patent introduces the PGW as an intermediary between the core network and the BS. The PGW handles packet buffering and coding adaptation, while the BS focuses on transmission. This intermediary role allows the system to maintain small BS buffers while still achieving reliable delivery and adaptive coding through the PGW's capabilities.
3Volume of stationary object
If credit-based flow control is used to achieve fine-grained control with small per-flow queues, then queue sizing is optimized, but this cannot always be implemented due to a lack of support between both end-points
Solution Approach 1:
The patent segments the flow control functionality between two distinct components: FlowON/FlowOFF messages for buffer status signaling, and credit-based transmission for actual packet flow control. This segmentation allows each mechanism to operate independently, achieving fine-grained control with small queues while maintaining compatibility with existing network infrastructure.
Solution Approach 2:
The patent changes the parameter representation from traditional credit-based counting to threshold-based FlowON/FlowOFF signaling. By using simple threshold comparisons (is buffer above high watermark? is buffer below low watermark?) instead of maintaining credit counters, the system achieves similar flow control effectiveness with reduced implementation complexity and better compatibility.
Data Source
AI summary
A method and apparatus controlling, either individually or in the aggregate, traffic flows associated with a plurality of queues by transmitting traffic source FlowON messages at first times selected to avoid queue underflow conditions, and traffic source FlowOFF message at second times selected to avoid queue overflow conditions, where the first and second times are determined as a function of delay time D of a link supporting the traffic source.