Near-End Receiver Flow Control Using AIOOS Codewords
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Solution Overview
Problem
DSL systems lack the capability to control far-end transmitter data transmission when near-end receivers' TC data buffers are at risk of overflowing, leading to data loss and increased latency due to retransmissions detected at higher layers.
Innovation Solution
Implementing a system where the near-end receiver generates an 'All Idle Out-Of-Sync' (AIOOS) codeword when its buffers approach capacity, instructing the far-end transmitter to pause data transmission until buffers clear, using high and low waterline thresholds to manage buffer fullness and prevent overflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the far-end transmitter continuously sends data to the near-end receiver, then the data transmission rate is improved, but the receiver's TC data buffers overflow causing data loss
Solution Approach 1:
The patent implements a feedback mechanism where the near-end receiver monitors its TC data buffer occupancy and sends flow control signals (AIOOS codewords) back to the far-end transmitter when the buffer approaches capacity. This feedback loop allows the receiver to dynamically control the transmitter's data rate, preventing buffer overflow while maintaining high transmission rates during normal operation.
Solution Approach 2:
The patent employs preliminary action by setting high and low waterline thresholds in advance within the receiver's buffer management system. When the buffer occupancy reaches the high waterline, the receiver proactively sends AIOOS signals to the transmitter before overflow occurs, instructing it to pause transmission. This preventive approach avoids data loss and retransmission delays.
2Reliability
If the receiver detects data loss at a higher layer, then data integrity is maintained, but significant latency is introduced due to retransmission
Solution Approach 1:
The patent prevents data loss before it occurs by implementing buffer occupancy monitoring with high waterline thresholds. The receiver proactively sends AIOOS flow control signals to the transmitter when the buffer approaches capacity, stopping transmission before overflow happens. This eliminates the need for later detection and retransmission, thereby maintaining data integrity without introducing retransmission latency.
3Reliability
If the near-end receiver controls the far-end transmitter to pause transmission, then buffer overflow is prevented, but data transmission is interrupted
Solution Approach 1:
The patent implements periodic flow control action rather than continuous interruption. The receiver monitors buffer occupancy continuously and sends AIOOS signals only when the high waterline is reached. Once the buffer level drops below the low waterline, transmission automatically resumes without interruption. This periodic on-off control prevents buffer overflow while minimizing transmission pauses.
Data Source
AI summary
Systems and methods are provided to enable a near-end receiver to control the far-end transmitter's data transmission such that the near-end receiver's TC data buffers do not overflow. In an embodiment, a high waterline and low waterline implemented into a near-end receiver are used to determine when the near-end receiver's TC data buffers are near maximum capacity. In an embodiment, the near-end receiver transmits a Packet Transfer Mode (PTM) All Idle Out Of Sync (AIOOS) codeword to the far-end transmitter when the high waterline is reached, and the near-end receiver stops transmitting the AIOOS codeword when the low waterline is reached.