Optical Network Modulation Switching by ONU Channel Quality
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Solution Overview
Problem
Existing optical networks struggle with inefficient modulation format management, as they typically use a single modulation format for all optical network units, leading to suboptimal bandwidth utilization and error correction, without considering the varying channel qualities of individual units.
Innovation Solution
An optical line terminal (OLT) organizes downstream transmission into frames with segments modulated in different formats, requesting channel quality estimation from units using a reference segment in a higher format, and adjusts modulation and FEC codes based on responses, allowing flexible format switching and optimized bandwidth utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single modulation format is used for all optical network units, then device complexity is reduced and ease of operation is improved, but bandwidth utilization efficiency deteriorates and network throughput is suboptimal
Solution Approach 1:
The patent applies local quality by assigning different modulation formats to different optical network units based on their individual channel qualities. Each ONU receives a modulation format tailored to its specific channel characteristics, optimizing bandwidth utilization for each unit rather than using a uniform format across all units.
Solution Approach 2:
The patent implements dynamics by enabling the OLT to dynamically switch modulation formats for each ONU based on real-time channel quality assessments. The system can adaptively change modulation formats in response to varying channel conditions, maximizing network throughput under different operational scenarios.
2Measurement precision
If channel quality estimation is performed based on currently assigned modulation format, then ease of operation is maintained, but measurement precision deteriorates and reliability of format support determination worsens
Solution Approach 1:
The patent applies preliminary action by having the OLT send reference segments modulated with candidate modulation formats before actually assigning those formats to ONUs. This allows the system to pre-assess channel quality for potential modulation formats, ensuring accurate measurements before committing to format assignments.
Solution Approach 2:
The patent uses reference segments as intermediaries to facilitate channel quality estimation. These reference segments, modulated with candidate formats, serve as a medium through which the OLT can accurately assess channel quality without directly assigning the candidate formats to ONUs, thus maintaining measurement precision while managing operational complexity.
3Productivity
If modulation format switching is enabled based on channel quality, then bandwidth utilization and network throughput are improved, but device complexity and difficulty of detecting and measuring channel quality increase
Solution Approach 1:
The patent applies segmentation by organizing downstream transmission into frames with distinct segments, where reference segments are specifically designated for channel quality estimation purposes. This segmentation allows the system to isolate and accurately measure channel quality for candidate modulation formats without interference from data transmission, facilitating informed format switching decisions.
Data Source
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Figure 3A~3B
AI summary
Example embodiments describe an optical line terminal, OLT, configured to communicate with optical network units, ONUs, (103, 104, 105, 106, 107) in a passive optical network (100). The downstream transmission from the OLT to the ONUs are organized in frames (110) comprising segments (111, 112, 113, 114, 115, 116), wherein a respective segment is modulated according to at least a first modulation format (111, 112, 114) or a second modulation format (113, 115, 116). The OLT being configured to perform sending (201), to at least one ONU (103), a request (202) to estimate (203) a channel quality based on at least one reference segment (213) modulated according to the second modulation format, wherein the at least one ONU (103) operates according to the first modulation format. The OLT further being configured to perform receiving, from the at least one ONU, a response (204) comprising an indication of the estimated channel quality; and deciding (205) to switch the segments in the downstream transmission assigned to the at least one ONU to the second modulation format based on the response. Further example embodiments describe an ONU configured to estimate a channel quality upon request by an OLT, a system comprising said OLT and said ONU, and a method for deciding to switch the modulation format assigned to at least one ONU.