CAP Signal Modulation for Bandwidth Efficiency
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Solution Overview
Problem
Existing signal modulation methods waste baseband bandwidth and have low resistance to dispersion due to high bandwidth requirements and inefficient spectral utilization, particularly in high-order modulation techniques like PAM-4, which also face challenges with carrier synchronization and algorithm complexity in OFDM.
Innovation Solution
The method involves demultiplexing an input signal into 2N sub-signals, grouping them into pairs for CAP modulation, and modulating these pairs to different frequency bands with orthogonal sub-signals, ensuring non-overlapping center frequencies, and performing electro-optic modulation, which reduces bandwidth waste and improves dispersion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-order modulation (PAM-4) is used to improve single-channel rate, then spectral efficiency is improved (2 bit/Hz to 4 bit/Hz), but bandwidth requirements increase and baseband bandwidth is wasted
Solution Approach 1:
The patent divides the baseband signal into multiple sub-signals with different center frequencies through filtering operations. Each sub-signal is modulated independently and then combined, creating a segmented frequency-domain representation that reduces bandwidth waste while maintaining high spectral efficiency
Solution Approach 2:
The patent transitions from time-domain modulation to frequency-domain modulation by applying filtering operations that create signals with different center frequencies. This dimensional change from time to frequency domain allows for more efficient bandwidth utilization
2Reliability
If conventional modulation with center frequency greater than spectral width is used, then modulation effect is achieved, but bandwidth waste in low frequency part occurs
Solution Approach 1:
The patent applies different filtering operations to create sub-signals with different local frequency characteristics. Each filtered sub-signal has a specific center frequency tailored to its spectral content, optimizing local bandwidth utilization while maintaining overall modulation effectiveness
Solution Approach 2:
The patent changes the frequency domain parameters of the modulated signal by applying filtering operations that shift center frequencies and adjust spectral distribution, thereby eliminating low-frequency bandwidth waste while preserving modulation integrity
3Productivity
If 400 GE/1 TE is implemented with excessively large quantity of parallel channels (400 GE/16 channels, 1 TE/40 channels), then channel quantity is increased, but reliability problem occurs
Solution Approach 1:
The patent segments the high-rate data stream into multiple lower-rate sub-signals that are modulated onto different frequency carriers. This segmentation reduces the complexity and reliability issues associated with excessively large quantities of parallel channels while maintaining high aggregate throughput
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach optimizes bandwidth utilization by reducing spectral waste and enhancing resistance to dispersion, allowing for more efficient data transmission with improved signal processing complexity.
Implementation Method 1
performing optical-to-electrical conversion on a received optical signal, to obtain N pairs of CAP signals by means of the conversion
Data Source
AI summary
The present invention discloses a signal modulation method, including: demultiplexing an input signal into 2N sub-signals; grouping every two of the 2N sub-signals into a pair; performing filtering on two sub-signals in each pair; performing carrierless amplitude phase (CAP) modulation on the two sub-signals in each pair; modulating the two sub-signals in each pair to a same frequency band, to generate N pairs of CAP signals, where frequency bands of different pairs of sub-signals are different, and a spacing between center frequencies of two neighboring frequency bands is greater than or equal to an average value of baud rates of sub-signals corresponding to the two neighboring frequency bands; and combining the N pairs of CAP signals, and performing electro-optic modulation on a signal obtained after the combining. A signal demodulation method corresponding to the signal modulation method is further disclosed.