Free-Space Optical Receiver Circuit Size Reduction
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Solution Overview
Problem
In free-space optical communication systems, the increase in transmission capacity is limited by the circuit size and cost of the digital signal processing unit, which grows proportionally with the number of eigenmodes processed, making it impractical to maintain communication stability with higher eigenmode counts.
Innovation Solution
A receiving device with multiple digital signal processing units, recording means, and an SN ratio estimating mechanism that dynamically controls signal processing based on the number of input signals and required combinations, optimizing processing order and reducing unnecessary processing to minimize circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of eigenmodes to be received is increased to reduce bit error rate, then communication reliability is improved, but the circuit size and cost of digital signal processing unit increases proportionally
Solution Approach 1:
The digital signal processing unit is divided into multiple independent processing channels, each handling a specific eigenmode. This segmentation allows parallel processing of multiple eigenmodes without requiring a proportional increase in the overall circuit size, as each segment can be independently optimized and reused.
Solution Approach 2:
The patent introduces a time-dimensional processing approach by implementing a buffer memory system that stores received signals and enables sequential reprocessing. This transforms the problem from a spatial complexity issue (more circuits for more eigenmodes) to a temporal processing issue (reusing the same circuits over time), effectively reducing the required circuit size while maintaining the ability to process multiple eigenmodes.
2Reliability
If the number of eigenmodes to be received is increased to reduce bit error rate, then communication stability is improved, but the cost of digital signal processing unit increases proportionally
Solution Approach 1:
The digital signal processing unit is designed with universal, reusable components that can process multiple eigenmodes through time-division multiplexing. The same processing circuits are reused across different time periods for different eigenmodes, eliminating the need for dedicated expensive hardware for each eigenmode and significantly reducing overall system cost.
Solution Approach 2:
The patent implements a buffer memory system that creates temporal copies of received signals, allowing the same processing circuits to be reused multiple times for the same or different eigenmodes. This copying approach in the time domain replaces the need for expensive parallel hardware copies, reducing manufacturing cost while maintaining processing capability.
3Productivity
If multiple digital signal processing means are used to process multiple input signals, then processing capability is improved, but circuit size increases
Solution Approach 1:
The patent implements periodic processing where a limited number of digital signal processing circuits repeatedly process different input signals over time cycles. The buffer memory enables the system to store incoming signals and feed them to the processing circuits in sequential batches, allowing the same circuits to handle multiple eigenmodes through periodic operation rather than requiring simultaneous dedicated circuits for each mode.
Data Source
AI summary
The objective of the present invention is to reduce the size of a receiving device circuit in an optical space communication system while maintaining communication stability. A data receiving device which decodes one item of data from a plurality of input signals includes: two or more digital signal processing means for subjecting the plurality of input signals to signal processing; a first recording means for temporarily recording the plurality of input signals; a SN ratio estimating means for estimating S/N ratios of each of the plurality of input signals and determining the number of the plurality of input signals to be combined, and the signals to be combined; and a scheduling means for carrying out overall control on the basis of the results from the SN ratio estimating means.