Flexible PON Modulation Switchover Using BER-Guided FEC Codewords
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Solution Overview
Problem
Existing communication networks in passive optical networks (PON) struggle to optimize throughput and reliability by adapting modulation formats based on varying channel conditions of individual user-devices, leading to suboptimal performance for both benign and harsh conditions.
Innovation Solution
A method and apparatus for an Optical Line Terminal (OLT) in a PON that dynamically switches between lower and higher order modulations based on bit error rate (BER) thresholds, using a hybrid modulation scheme with mixed FEC codewords to ensure reliable communication, allowing devices under better conditions to utilize higher throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher order modulation is used to increase throughput, then productivity is improved, but reliability deteriorates due to higher bit error rates
Solution Approach 1:
The system dynamically changes the modulation order parameter based on channel conditions. When channel conditions are good (low BER), higher order modulation is used to maximize throughput. When channel conditions deteriorate (high BER), the system switches to lower order modulation to maintain reliability, thus resolving the contradiction between productivity and reliability through adaptive parameter adjustment
Solution Approach 2:
The modulation scheme is made dynamic rather than fixed. The system continuously monitors BER and adjusts the modulation order in real-time based on feedback about channel conditions. This dynamic adaptation allows the system to optimize the trade-off between throughput and reliability according to actual operating conditions
2Ease of operation
If fixed modulation format is used to simplify system operation, then ease of operation is improved, but adaptability deteriorates to varying channel conditions
Solution Approach 1:
The system transitions from a static fixed modulation format to a dynamic adaptive modulation scheme. The OLT automatically adjusts the modulation order based on BER feedback from ONUs, enabling the system to adapt to varying channel conditions while maintaining relatively simple operation through automated decision-making
Solution Approach 2:
The system implements a feedback mechanism where ONUs report their BER measurements to the OLT, which then uses this information to adjust the modulation format. This feedback loop enables adaptability to channel conditions while keeping the control logic centralized and manageable
3Productivity
If modulation switching is implemented to optimize throughput, then productivity is improved, but device complexity increases
Solution Approach 1:
The complexity is managed by focusing on changes in a single key parameter - the modulation order - rather than implementing complex multi-parameter adaptation. The system switches between discrete modulation orders (e.g., PAM4, PAM8) based on BER thresholds, which simplifies the switching mechanism while still achieving significant throughput optimization
Solution Approach 2:
The modulation switching mechanism is segmented into distinct phases: rate determination phase where BER is measured and compared against thresholds, and data transmission phase where the selected modulation is applied. This segmentation of the control logic into manageable phases reduces overall system complexity
Data Source
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AI summary
A network element includes at least one processor and at least one memory. The at least one non-transitory memory including computer program code configured to, when executed by the at least one processor, cause the apparatus to determine whether a bit error rate (BER) of a FEC codeword is at or below a correctable BER, wherein the FEC codeword is transmitted between an OLT and ONU, a first percentage of the FEC codeword is at a lower order modulation, and a second percentage of the FEC codeword is at a higher order modulation, establish, based on a determination that the BER is at or below the correctable BER, a connection between the OLT and the ONU at the higher order modulation, and maintain, based on a determination that the BER is greater than the correctable BER, the connection between the OLT and the ONU at the lower order modulation.