DSP Interleaving for Free Space Optical Link Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Atmospheric turbulence in free space optical communications causes random fluctuations in received optical power, leading to errors in data transmission, even with sophisticated error correction engines, thereby limiting the availability of free space optical links.
Innovation Solution
A digital signal processor (DSP) is used to encode original streams of protocol data units (PDUs) into encoded streams via forward error correction (FEC) encoding and interleaving, decoupling interleaving from the transmission chain and performing FEC at a layer above the physical layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sophisticated error correction engines are used, then error correction capability is improved, but signal power availability is still insufficient due to atmospheric turbulence
Solution Approach 1:
The patent applies preliminary action by performing interleaving before transmission to separate successive data blocks in time by at least 10 milliseconds. This pre-processing arrangement ensures that when atmospheric turbulence causes power fluctuations, the error correction engine can effectively handle the errors because the affected data blocks are separated in time, allowing the system to maintain reliability even when signal power availability varies.
2Productivity
If data blocks are transmitted continuously, then transmission efficiency is improved, but atmospheric turbulence causes successive data blocks to be affected simultaneously
Solution Approach 1:
The patent applies segmentation by dividing the continuous data stream into separate substreams and interleaving them. Successive data blocks from different substreams are separated in time by at least 10 milliseconds. This segmentation maintains transmission efficiency by keeping data flowing continuously while improving reliability by ensuring that atmospheric turbulence affecting one time period does not simultaneously affect all data blocks.
Solution Approach 2:
The patent implements periodic action through the interleaving process, which systematically separates data blocks in time with a period of at least 10 milliseconds between successive data blocks from the same substream. This periodic separation pattern ensures that data transmission continues efficiently while protecting against turbulence-induced errors that occur over shorter time scales.
3Reliability
If interleaving separates data blocks by at least 10 milliseconds, then atmospheric turbulence effects are mitigated, but transmission delay increases
Solution Approach 1:
The patent applies partial action by implementing interleaving with a specific separation period of at least 10 milliseconds, which is sufficient to mitigate atmospheric turbulence effects without excessive delay. This optimized separation duration provides the necessary turbulence mitigation while minimizing the impact on transmission delay, achieving a balanced compromise between reliability and time loss.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A digital signal processor (DSP) for encoding an original stream of protocol data units (PDUs) into one or more encoded streams of PDUs to be transmitted via a free space optical link, wherein the DSP is configured to generate the one or more encoded streams of PDUs from the original stream of PDUs by forward error correction (FEC) encoding and interleaving.