Asymmetric Clocking for EPON Line Rate Adaptation
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Solution Overview
Problem
Current Ethernet passive optical networks (EPONs) lack the ability to support asymmetric line rates, which limits the service providers' capability to offer diversified services as they are restricted to symmetric line rates of 1.25 Gbps for both upstream and downstream communications, failing to match the increasing demand for high-bandwidth internet traffic.
Innovation Solution
The implementation of a method and apparatus that utilize different code-group clocks for downstream and upstream transmissions, along with a multi-point control protocol (MPCP) clock, allowing for asymmetric line rates by operating the downstream code-group clock at a higher rate than the upstream code-group clock, enabling faster downstream transmission rates while maintaining the MPCP clock frequency ratio, thereby facilitating data multiplexing and demultiplexing to achieve effective data rates of 2.5 Gbps downstream and 1.25 Gbps upstream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If symmetric line rates of 1.25 Gbps are used for both upstream and downstream communications, then the EPON system maintains simplicity and compliance with IEEE 802.3ah standard, but the system cannot accommodate increasing demand for high-bandwidth internet traffic and diversified services
Solution Approach 1:
The patent applies asymmetry by implementing different line rates for upstream and downstream communications. Specifically, the downstream communication operates at 2.5 Gbps while the upstream communication operates at 1.25 Gbps, breaking the traditional symmetric constraint. This allows the system to provide higher bandwidth for downstream traffic which typically carries more data-intensive content like video and web pages, while maintaining adequate upstream bandwidth for interactive applications.
Solution Approach 2:
The patent implements dynamics by introducing separate code-group clocks for upstream and downstream directions. The downstream code-group clock operates at a higher frequency (2.5 Gbps) compared to the upstream code-group clock (1.25 Gbps), allowing each direction to be independently optimized based on traffic requirements. This dynamic approach enables flexible bandwidth allocation without requiring changes to the fundamental EPON architecture.
2Productivity
If asymmetric line rates are implemented with different code-group clocks for upstream and downstream, then the system can provide diversified services with higher downstream bandwidth, but the system complexity increases due to multiple clock frequencies
Solution Approach 1:
The patent applies segmentation by separating the clocking mechanisms into independent upstream and downstream code-group clocks. Instead of using a single unified clock, the system divides the timing function into two independent clock domains, each optimized for its respective direction. This segmentation allows each clock to operate at its optimal frequency without interfering with the other, simplifying the overall synchronization approach despite the asymmetry.
Solution Approach 2:
The patent uses the MPCP (Multi-Point Control Protocol) as an intermediary to manage the asymmetric clocking. The MPCP clock serves as a mediator that coordinates between the upstream code-group clock and downstream code-group clock, handling frame synchronization and timing alignment. This intermediary approach abstracts the complexity of asymmetric clocking, allowing standard EPON protocols to operate while supporting asymmetric line rates.
Data Source
AI summary
One embodiment of the present invention provides a method for facilitating asymmetric line rates in an Ethernet passive optical network (EPON) which includes a central node and at least one remote node. During operation, the system provides a downstream code-group clock, wherein each cycle thereof corresponds to a code group transmitted from the central node to a remote node. The system also provides an upstream code-group clock, wherein each cycle thereof corresponds to a code group received at the central node from a remote node. In addition, the system provides a multi-point control protocol (MPCP) clock, wherein the frequency ratio of the MPCP clock to the downstream code-group clock is different from the frequency ratio of the MPCP clock to the upstream code-group clock, thereby allowing the downstream transmission to be performed at a faster line rate than the upstream transmission line rate.