Upstream Scheduling in Passive Optical Networks
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Solution Overview
Problem
The coexistence of 10G-EPON and 1G-EPON systems in the upstream direction is inefficient due to overlapping wavebands, requiring conventional pure time-division multiple access (TDMA) techniques, which do not fully utilize the potential for combined TDMA and wavelength-division multiple access (WDMA) scheduling.
Innovation Solution
The system determines which 1G-ONUs transmit in non-overlapping wavebands with 10G-ONUs and schedules them in a combined TDMA and WDMA manner, while scheduling other 1G-ONUs in a pure TDMA fashion to avoid interference, exploiting the fact that 1G-ONUs often occupy narrow wavebands not overlapping with 10G-EPON standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure TDMA scheme is used to separate upstream transmissions of 10G-EPON and 1G-EPON systems, then waveband overlap interference is avoided, but bandwidth utilization efficiency deteriorates
Solution Approach 1:
The patent segments the upstream transmission schedule into different time slots and wavelength assignments based on ONU type (10G-EPON or 1G-EPON) and waveband characteristics. By dividing the transmission opportunity into structured segments with specific time-wavelength combinations, the system achieves both interference avoidance for overlapping wavebands and efficient utilization for non-overlapping ones.
Solution Approach 2:
The patent transitions from pure time-division (one dimension) to a combined time-wavelength division approach (two dimensions). This dimensional expansion allows simultaneous transmissions in different wavelength bands during the same time slot, dramatically improving bandwidth utilization while maintaining interference avoidance through coordinated scheduling.
2Productivity
If 1G-ONUs transmit in narrow wavebands not overlapping with 10G-EPON, then coexistence efficiency improves, but scheduling complexity increases
Solution Approach 1:
The patent changes the scheduling parameters from simple time slots to combined time-wavelength assignments. By introducing wavelength as an additional scheduling parameter, the system can exploit the narrow waveband characteristics of 1G-ONUs to create non-overlapping transmission opportunities with 10G-EPON systems, improving coexistence efficiency while managing complexity through structured parameter assignment.
3Productivity
If combined TDMA and WDMA scheduling is implemented, then bandwidth usage is optimized, but interference management difficulty increases
Solution Approach 1:
The patent incorporates feedback mechanisms where ONUs report their waveband characteristics and transmission requirements to the OLT. This feedback enables the OLT to dynamically adjust the combined TDMA-WDMA schedule, optimizing bandwidth usage while managing interference through adaptive reconfiguration based on actual transmission conditions.
Data Source
AI summary
In general, the 1G-EPON standard specifies its upstream waveband broadly to allow for low cost lasers to be used to transmit upstream. Often, however, the lasers actually used by many 1G-ONUs to transmit upstream only occupy a narrow waveband that does not overlap with the upstream waveband specified by the 10G-EPON standard. The present disclosure is directed to systems and methods that exploit this fact to efficiently provide for the coexistence of 10G-EPON and 1G-EPON over the same set of optical fibers in the upstream direction.