Multi-band OFDM OLT Sub-band Segmentation for Cost Reduction
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Solution Overview
Problem
The existing single-band OFDM PON scheme faces high device costs, compatibility issues with ODN, and non-colorless ONU due to stringent requirements on digital-to-analog and analog-to-digital conversion for downstream data transmission, and upstream signal isolation through wavelength division multiplexing.
Innovation Solution
The proposed solution involves dividing the downstream data transmission frequency band into multiple sub-bands, using a multi-band OFDM PON network framework that employs frequency division multiplexing, allowing each sub-band to perform OFDM modulation independently, and enabling sub-band bandwidth sharing among ONUs, with OLT control for dynamic allocation and guard band management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If single-band OFDM PON is used for downstream data transmission, then spectrum efficiency is improved, but device cost increases due to high sampling rate requirements for digital-to-analog conversion and IQ modulation
Solution Approach 1:
The downstream frequency band is divided into multiple sub-bands, with each sub-band processed by a separate parallel data transmission processing unit. This segmentation allows each unit to operate at a lower sampling rate, reducing the cost of digital-to-analog conversion and IQ modulation devices while maintaining overall high spectrum efficiency through the combined bandwidth of all sub-bands.
2Speed
If high-speed optical devices are used to achieve high data transmission rates, then transmission speed is improved, but device cost increases due to integration level and manufacturing process constraints
Solution Approach 1:
The high data transmission rate is achieved by parallel processing of multiple sub-bands, each at a lower, more cost-effective sampling rate. The aggregate throughput of all parallel units equals or exceeds what a single high-speed device would provide, but at significantly lower cost per unit.
Solution Approach 2:
The system changes the operating parameters of the transmission processing units from high sampling rates to multiple lower sampling rates. This parameter change enables the use of lower-cost devices while maintaining the required overall transmission capacity through parallel aggregation.
3Reliability
If wavelength division multiplexing is used for upstream signal isolation, then signal interference is reduced, but device complexity increases and ONU colorlessness is lost
Solution Approach 1:
The system uses time-division multiplexing with periodic time slots allocated to different ONUs for upstream transmission. Each ONU transmits in its designated time slot, providing signal isolation through temporal separation rather than spectral separation, thereby maintaining ONU colorlessness and reducing device complexity.
Data Source
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AI summary
The present document provides an optical line terminal (OLT), which includes: an OLT control unit configured to divide a downstream data transmission frequency band into a plurality of sub-bands; a serial-to-parallel conversion unit configured to, according to a division of the OLT control unit, perform a serial-to-parallel conversion on data to be transmitted to obtain data of the plurality of sub-bands, and transmit the data of each sub-band to a corresponding downstream data transmission processing unit; a downstream data transmission processing unit configured to map and modulate the corresponding sub-band data and output radio frequency signals; a combiner unit configured to combine a plurality of radio frequency signals and output combined signals; and an optical transmission processing unit configured to convert the combined signals into optical signals and transmit the optical signals. The present document also provides a data transmission method. With the present document, the downstream transmission frequency band is divided into a plurality of sub-bands, the sampling rates of the digital-to-analog conversion and IQ modulation devices required by each sub-band are lower than the sampling rates of devices required by the single-band scheme, thereby reducing the cost of system implementation.