Downstream Flow Control in xGPON Systems
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Solution Overview
Problem
Current (x)GPON systems lack a downstream flow control mechanism, leading to increased memory size and power consumption in ONUs due to buffering requirements during congestion, as they rely solely on upstream control mechanisms.
Innovation Solution
Introduction of a new PLOAM message, DS_FlowControl_Request, allowing ONUs to request OLTs to inhibit downstream transmission for a specified period, enabling reduced buffer sizes and power consumption by implementing downstream flow control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ONU buffers traffic for 100ms during congestion, then downstream transmission reliability is maintained, but memory size and power consumption increase
Solution Approach 1:
The patent implements a feedback mechanism where the ONU monitors its buffer status and sends DS_FlowControl_Request messages to the OLT when buffer occupancy exceeds a threshold. The OLT responds by suspending downstream transmissions, creating a closed-loop control system that maintains reliability while minimizing buffer requirements and power consumption.
Solution Approach 2:
The patent applies preliminary action by having the ONU proactively send flow control requests before the buffer becomes completely full. This preventive approach allows the system to maintain reliability by anticipating congestion conditions, while avoiding the need for large buffers and reducing power consumption through early intervention.
2Quantity of substance
If ONU supports downstream flow control, then buffer size can be reduced, but system complexity increases due to new message mechanisms
Solution Approach 1:
The patent achieves universality by extending the existing PLOAM message framework to carry flow control functionality. The DS_FlowControl_Request message leverages the established PLOAM infrastructure, allowing the system to reduce buffer sizes while minimizing the increase in complexity through multi-functional use of existing protocols.
3Quantity of substance
If OLT inhibits downstream transmission, then ONU buffer requirements are reduced, but downstream transmission efficiency decreases
Solution Approach 1:
The patent applies periodic action through time-limited flow control suspensions. The OLT inhibits downstream transmissions for specific durations based on the transmission inhibiting period parameter in the DS_FlowControl_Request message, allowing the ONU to drain its buffer. This periodic suspension reduces buffer requirements while minimizing the impact on overall transmission efficiency through controlled, temporary pauses.
Data Source
Figure 1
AI summary
The invention provides a method and apparatus for downstream flow control in an (x)GPON System. First, ONU sends a DS_FlowControl_Request message to OLT, wherein the DS_FlowControl_Request message includes information of transmission inhibiting period and is used for requesting OLT to inhibit downstream transmission for a transmission inhibiting period corresponding to the information of transmission inhibiting period. After receiving the DS_FlowControl_Request message from ONU, OLT inhibits the downstream transmission for the transmission inhibiting period corresponding to the information of transmission inhibiting period based on the information of transmission inhibiting period included in the DS_FlowControl_Request message. After inhibiting the downstream transmission for the transmission inhibiting period corresponding to the information of transmission inhibiting period, OLT résumes the downstream transmission to ONU.