Optical Transmitter Subcarrier Allocation for Multipath Interference
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Solution Overview
Problem
Existing optical transmission systems using the DMT scheme face challenges in securing a communication link due to subcarrier degradation from multipath interference and varying frequency characteristics, leading to unreliable data transmission and reduced capacity.
Innovation Solution
An optical transmission system that includes a control unit to measure and allocate subcarriers based on transmission characteristics, using a measurement signal to select subcarriers with excellent frequency performance and minimal impact on transmission capacity, thereby optimizing the communication link.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If subcarrier allocation is performed without measurement in conventional DMT systems, then device complexity is reduced, but transmission reliability deteriorates due to subcarrier degradation from multipath interference and varying frequency characteristics
Solution Approach 1:
The system performs preliminary measurement signal transmission before actual data communication to assess subcarrier quality. The control unit transmits measurement signals on each subcarrier, evaluates the received signal quality at the optical receiver, and pre-determines which subcarriers are suitable for communication based on measured characteristics such as signal-to-noise ratio and interference levels.
Solution Approach 2:
The optical receiver measures the quality of measurement signals received on each subcarrier and feeds back this information to the control unit. Based on this feedback regarding subcarrier quality (including effects of multipath interference and frequency characteristics), the control unit makes informed decisions about subcarrier allocation, ensuring reliable communication links are established.
2Measurement precision
If measurement signals are transmitted on all subcarriers, then transmission characteristics are accurately measured, but transmission capacity is reduced due to bandwidth consumption by measurement signals
Solution Approach 1:
The system extracts only the necessary measurement information from subcarrier signals to assess transmission characteristics. Rather than requiring continuous measurement signal transmission on all subcarriers, the system performs measurements during initial link establishment or periodic intervals, then uses this extracted information to determine subcarrier allocation for data transmission.
Solution Approach 2:
The system transmits measurement signals on a partial set of subcarriers rather than all subcarriers continuously. The control unit selects representative subcarriers or subsets of subcarriers for measurement based on frequency characteristics and interference patterns, achieving sufficient measurement precision while minimizing the impact on overall transmission capacity.
Data Source
AI summary
An optical transmission system is configured to optically transmit data from an optical transmitter to an optical receiver using a plurality of subcarriers. The optical transmitter includes a control unit configured to transmit a measurement signal using a subcarrier included in a band used for optical transmission when a signal is communicated to the optical receiver, the control unit being configured to calculate transmission characteristics obtained between the optical transmitter and the optical receiver based on the measurement signal returned from the optical receiver, and the control unit being configured to allocate, based on the transmission characteristics, a communication link to a subcarrier excellent in the transmission characteristics and least affecting transmission capacity. The optical receiver is configured to return the measurement signal received thereby to the optical transmitter.