Adaptive Bit Loading in Optical OFDM Systems
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Solution Overview
Problem
In optical OFDM systems, high bit error rates and significant SNR degradation in subcarriers due to noise interference lead to poor system performance, particularly when a large number of subcarriers experience SNR degradation.
Innovation Solution
A communication method where the receive end determines modulation order information and power information for subcarriers experiencing SNR degradation and sends a trimmer request message to the transmit end, which adjusts the modulation and power allocation accordingly, using a trimmer request message that includes subcarrier indices, bit mapping parameters, and power allocation parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fixed modulation and power allocation is used in optical OFDM systems, then system implementation is simple, but system performance degrades when SNR degradation occurs in subcarriers due to noise interference
Solution Approach 1:
The patent implements dynamic modulation order and power allocation for subcarriers based on real-time SNR measurements. The system transitions from fixed to adaptive parameters, where modulation order and power allocation are adjusted according to channel conditions, resolving the contradiction between simple implementation and good performance under varying SNR conditions
Solution Approach 2:
The patent changes the parameters of modulation order and power allocation dynamically based on SNR conditions. When SNR degradation is detected in subcarriers, the system adjusts these parameters to optimize performance, directly addressing the technical contradiction by making parameters adaptive rather than fixed
2Reliability
If adaptive modulation and power allocation is implemented to improve system performance, then bit error rate decreases, but communication overhead increases due to trimmer request messages and signaling
Solution Approach 1:
The patent applies local quality by implementing adaptive modulation and power allocation only for subcarriers experiencing SNR degradation, rather than uniformly across all subcarriers. The trimmer request messages are generated selectively based on local channel conditions, reducing overall communication overhead while maintaining low bit error rates where needed
Solution Approach 2:
The patent implements a feedback mechanism where the receive end monitors SNR conditions and generates trimmer request messages when degradation is detected. This feedback loop enables adaptive adjustment of modulation and power allocation parameters, achieving low bit error rates through selective signaling rather than continuous overhead
3Reliability
If a large number of subcarriers experience SNR degradation, then system performance severely deteriorates, but increasing power allocation to compensate increases total power consumption
Solution Approach 1:
The patent applies local quality by allocating additional power only to subcarriers experiencing SNR degradation, rather than uniformly increasing power across all subcarriers. This selective power allocation maintains system performance in affected subcarriers while minimizing total power consumption increases
Solution Approach 2:
The patent dynamically changes power allocation parameters based on SNR conditions of individual subcarriers. When SNR degradation occurs, power allocation is increased locally for affected subcarriers, optimizing the balance between system performance and total power consumption through parameter adaptation
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AI summary
Embodiments of the present invention disclose a communication method, a transmit end, and a receive end. The method of the embodiments of the present invention includes: in a case in which at least one of conditions that a system bit error rate is lower than a preset threshold, and a quantity of subcarriers, on which signal to noise ratio (SNR) degradation occurs, in an optical signal exceeds a predetermined numerical range is satisfied, determining, by a receive end according to an SNR of a to-be-adjusted subcarrier, modulation order information and power information that correspond to the to-be-adjusted subcarrier; sending, by the receive end, a trimmer request message to a transmit end, where the trimmer request message includes the modulation order information and the power information that correspond to the to-be-adjusted subcarrier; receiving, by the receive end, an effective time point sent by the transmit end; and receiving, by the receive end, a subcarrier at the effective time point by using a demodulation order corresponding to the to-be-adjusted subcarrier. In the embodiments of the present invention, modulation order information and power information that correspond to a subcarrier, on which degradation occurs, in subcarriers of an optical transmit signal are adjusted by using a trimmer request message, thereby improving system performance.