OLT Terminal Sorting Unit for TWDM-PON Switching
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Solution Overview
Problem
In TWDM-PON systems, dynamic connection switching between OLT and ONU during downlink communication can result in packet loss due to the need for buffering packets during switching, leading to increased circuit size and memory requirements as the number of ONUs increases, which is economically and feasibly problematic.
Innovation Solution
The OLT employs a sorting unit with through queues, switch queues, and a scheduler to manage unicast and broadcast packets, limiting the number of ONUs undergoing simultaneous switching and reducing memory needs by using a learning table to optimize packet routing and buffer usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If buffering packets at OLT during switching time period is implemented to prevent packet loss, then service quality is improved, but circuit size and memory requirements increase
Solution Approach 1:
The patent applies preliminary action by having the OLT buffer packets for switch-target ONUs before switching occurs. The control device identifies which ONUs are undergoing wavelength switching and pre-buffers their packets in the buffer unit, ensuring no packet loss during the switching time period. This resolves the contradiction by preparing buffer allocations in advance based on switching status rather than maintaining large buffers for all possible scenarios.
Solution Approach 2:
The patent implements local quality by allocating buffer resources selectively rather than uniformly. The control device determines which specific ONUs are in switching state and allocates buffer space only for those particular ONUs' packets. This localized buffering approach prevents unnecessary memory consumption while ensuring service quality for affected ONUs, directly addressing the contradiction between reliability and device complexity.
2Adaptability or versatility
If the number of ONUs increases to provide more services, then adaptability is improved, but memory requirements for address management increase
Solution Approach 1:
The patent applies local quality by implementing selective buffering based on switching status. Rather than maintaining buffer allocations for all ONUs regardless of state, the control device identifies only those ONUs currently undergoing wavelength switching and allocates buffer resources specifically for them. This reduces overall memory requirements while maintaining the ability to serve an increasing number of ONUs.
Solution Approach 2:
The patent implements partial action by applying buffering only to the extent necessary - specifically for packets destined for ONUs in switching state. This partial buffering approach avoids the excessive memory consumption that would result from buffering all packets or maintaining buffers for all possible ONUs, thereby supporting system scalability without linearly increasing memory requirements.
Data Source
AI summary
A station-side terminal apparatus comprises terminal devices and a terminal device sorting unit. The terminal devices includes: a buffer unit; a subscriber-side terminal apparatus sorting unit configured to transmit a unicast packet addressed to a switch-target subscriber-side terminal apparatus to the switch queues, and transmit a packet addressed to a plurality of subscriber-side terminal apparatuses to the broadcast queue, and transmit a unicast packet addressed to a non-switch-target subscriber-side terminal apparatus to the through queue; and a scheduler unit configured to read a packet from the switch queues, the broadcast queue, and the through queue. The terminal device sorting unit is configured to transmit a received unicast packet to the terminal device, and transmit a received packet addressed to a plurality of subscriber-side terminal apparatuses, to each of the terminal devices.