Timestamp Adjustment in MPCP Messages for EPoC Networks
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Solution Overview
Problem
The existing Ethernet Passive Optical Network (EPON) technologies face challenges in accurately measuring Round Trip Time (RTT) in unified optical-coaxial networks due to the lack of consideration for coaxial network delays, leading to timing drift and inefficient upstream bandwidth allocation.
Innovation Solution
The proposed solution involves adjusting Multi-Point Control Protocol (MPCP) message timestamps at a Fiber Coaxial Unit (FCU), Coaxial Network Unit (CNU), or Optical Line Terminal (OLT) to account for coaxial delays, ensuring accurate RTT measurement and incorporation of these delays into the network scheduler for efficient resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If EPON timestamp adjustment mechanisms are applied to EPoC networks without considering coaxial network delays, then the device complexity is reduced by reusing existing protocols, but the measurement precision of RTT deteriorates due to unaccounted coaxial delays
Solution Approach 1:
The patent modifies the timestamp parameter in MPCP messages by introducing a coaxial delay compensation value. The FCU adjusts the timestamp by adding or subtracting the coaxial delay parameter depending on the message direction (upstream or downstream), thereby correcting the RTT measurement accuracy while maintaining protocol reuse
Solution Approach 2:
The FCU acts as an intermediary device between the OLT and CNU that performs timestamp adjustment. It receives MPCP messages, modifies the timestamp field by applying coaxial delay compensation, and forwards the adjusted messages, thereby resolving the measurement precision issue without requiring changes to the core EPON protocol
2Measurement precision
If coaxial delay compensation is implemented in timestamp adjustment, then the measurement precision of RTT is improved, but the device complexity increases due to additional delay measurement and calculation mechanisms
Solution Approach 1:
The patent performs preliminary measurement of coaxial network delay during the initial network setup phase. The FCU measures the one-way delay through the coaxial network and stores this compensation value for subsequent RTT calculations, thereby avoiding repeated complex measurements while improving precision
Solution Approach 2:
The FCU automatically performs the timestamp adjustment using the pre-measured coaxial delay parameter. The device self-manages the delay compensation process by intercepting MPCP messages, applying the stored delay value to adjust timestamps, and forwarding modified messages without requiring external intervention or complex real-time calculations
3Productivity
If upstream bandwidth allocation is performed without accounting for coaxial delays, then the productivity of bandwidth management is maintained through simple scheduling, but the reliability of resource allocation deteriorates due to timing drift
Solution Approach 1:
The patent implements a feedback mechanism where the FCU continuously monitors and measures the actual coaxial network delay, then uses this measured value to adjust upstream bandwidth allocation timing. The OLT receives adjusted MPCP messages with corrected timestamps, enabling accurate RTT-based scheduling that accounts for coaxial delays, thereby improving allocation reliability while maintaining efficiency
Data Source
AI summary
A method performed by a FCU comprising receiving a MPCP request message from a CNU via an electrical network, wherein the MPCP request message comprises a first timestamp, adjusting the first timestamp in the MPCP request message by an electrical network delay, and forwarding the MPCP request message with the adjusted timestamp to an OLT via an optical network. Also disclosed is a method performed by an OLT comprising receiving a MPCP message from a CNU via a FCU and an optical network, obtaining an arrival time of the MPCP message, adjusting a timestamp in the MPCP message by subtracting an electrical network delay from the timestamp, and computing a RTT delay based on the timestamp and the arrival time.