Central-Office Termination Apparatus for Uninterrupted Path Switching
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Solution Overview
Problem
In TWDM-PON systems, packet loss occurs during adaptive connection switching due to the need for increased buffer capacity and circuit scale as the number of ONUs increases, which is impractical and memory-intensive.
Innovation Solution
The OLT employs a central-office termination apparatus with a scheduler and buffer system that includes through queues and switching queues, where packets destined for ONUs under switching are routed through switching queues, reducing the number of queues and memory required for address management, allowing for uninterrupted switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If buffer capacity is increased to prevent packet loss during switching, then reliability is improved, but device complexity and memory requirements increase
Solution Approach 1:
The buffer is segmented into multiple queues (through queue and switching queues) organized in a tree structure. Each queue handles specific packet types or destination groups, allowing the system to manage buffering requirements selectively rather than providing uniform high-capacity buffering for all packets. This segmentation reduces the total buffer capacity needed while maintaining reliability for critical packets.
Solution Approach 2:
The patent introduces a hierarchical tree structure for organizing queues, adding a dimensional aspect to buffer management. Instead of a flat buffer structure, packets are routed through multiple levels of queues (through queue → switching queues → destination queues), which distributes the buffering burden across different hierarchical levels and reduces peak memory requirements.
2Adaptability or versatility
If the number of queues is increased to handle more ONUs simultaneously, then adaptability is improved, but memory capacity requirements increase
Solution Approach 1:
Multiple destination queues are merged into shared switching queues at intermediate hierarchical levels. Instead of providing dedicated queues for each ONU, the system combines traffic from multiple destinations into shared queues, reducing the total number of queues and their associated memory requirements while maintaining the ability to serve multiple ONUs simultaneously.
Solution Approach 2:
The switching queues serve multiple functions: they act as aggregation points for packets destined for multiple ONUs, provide temporary buffering during wavelength switching, and enable load distribution across different optical transmitter/receiver pairs. This multi-functionality reduces the need for specialized queues for each function, decreasing overall memory capacity requirements.
Data Source
AI summary
A central-office termination apparatus includes plural termination devices and a termination device distributor. Each termination device includes a buffer, a subscriber-terminal terminator distributor and a scheduler. The buffer has a through queue and one or more switching queues. The subscriber-terminal terminator distributor transfers a packet meant for one subscriber-terminal terminator under switching to the switching queue, and transfers another packet meant for another subscriber-terminal terminator not under switching to the through queue. The scheduler reads out packets from the switching and through queues. The termination device distributor transfers a received packet to a termination device having the subscriber-terminal terminator registered for which that packet is meant.