DSL Transceiver Flow Control via Buffer Segmentation
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Solution Overview
Problem
Existing DSL transceivers face challenges in managing varying data rates among multiple subscribers connected to a single fiber link, leading to potential packet drops and quality of service issues due to lack of effective flow control and back pressure mechanisms.
Innovation Solution
The implementation of a DSL transceiver with a processing unit that determines and communicates average data rates to a passive optical network element, using signaling mechanisms like Xon/Xoff signals and ITU standards to manage buffer storage and allocate memory dynamically based on subscriber data rates, enabling seamless connectivity and quality of service.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a common pool memory is shared for multiple interfaces in the PON element, then memory utilization is improved, but packet loss increases when one interface experiences a link drop
Solution Approach 1:
The patent segments the common pool memory into dedicated buffer regions for each interface/port. When a link drop occurs on one interface, only that interface's buffer is affected while other interfaces continue to operate normally using their dedicated buffer space, preventing packet loss on healthy interfaces.
Solution Approach 2:
The patent pre-allocates buffer space for each interface within the common pool memory before link drops occur. This preliminary allocation ensures that when a link drop happens, the affected interface has its own reserved buffer space ready, preventing it from consuming memory that would be needed by other active interfaces.
2Reliability
If the PON element accumulates packets for an interface with a link drop, then packet delivery is improved, but memory storage is bloated and affects other services
Solution Approach 1:
The patent segments the memory storage into interface-specific buffer regions. When packets need to be accumulated due to a link drop, they are stored only in the affected interface's dedicated buffer region, not in the entire common pool. This segmentation prevents memory bloat from affecting other services while still ensuring reliable packet delivery for the affected interface.
3Device complexity
If the DSL transceiver operates without knowledge of individual subscriber data rates, then device complexity is reduced, but flow control precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the DSL transceiver measures and determines the actual data rate for each subscriber connection, then communicates this information to the PON element. This feedback loop enables the PON element to perform precise flow control and buffer allocation based on real-time data rate information, improving flow control precision without significantly increasing device complexity.
4Reliability
If a back pressure mechanism is established between OLT and PON element, then quality of service is improved, but device complexity increases
Solution Approach 1:
The patent establishes a back pressure mechanism through feedback signaling between the OLT and PON element. When the PON element's buffers are approaching capacity or when flow control is needed, it sends feedback signals to the OLT to slow down or pause data transmission. This feedback-based back pressure mechanism improves quality of service by preventing buffer overflow and packet loss, while maintaining relatively simple device architecture by using existing signaling channels.
Data Source
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AI summary
A Digital Subscriber Line, DSL/G.fast/G.hn, transceiver comprising a plurality of first interfaces configured to transmit data packet streams in a downlink direction to different subscribers and to receive data packet streams from the different subscribers, a second interface configured to transmit data packet streams in an uplink direction to a passive optical network element, and at least one processing unit configured to detect a physical layer indicator of a loss of signal of one of the first interfaces received at a physical layer at said one first interface, wherein when the at least one processing unit detects the physical layer indicator for said one first interface, the second interface transmits the physical layer indicator in the uplink direction to the passive optical network element.