Adaptive R-PHY MAP Advance Timing for Cable Modem Scheduling
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Solution Overview
Problem
In R-PHY distributed access architectures, synchronously coordinating transmissions between the CCAP core and cable modems is challenging due to unpredictable latency in the packet switched network, making it difficult to calculate the delay between sending MAP messages and their receipt at the cable modems.
Innovation Solution
A method using data from MAP messages to estimate delay and adjust MAP advance time, involving synchronization of clocks and utilization of latency measurement protocols like DEPI or PTP, with adaptive adjustment of MAP advance times based on measured latency thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If R-PHY distributed access architecture is used to spread CMTS functionality throughout the network, then network congestion at head end is reduced and digital signal transmission is extended deeper into the network, but synchronously coordinating transmissions between downstream cable modems and CCAP core becomes much more difficult due to unpredictable latency in packet switched network
Solution Approach 1:
The patent implements feedback mechanisms where the R-PHY device measures actual latency between receiving MAP messages and when the corresponding transmission window occurs, then reports this measured latency back to the CMTS. The CMTS uses this feedback to dynamically adjust the MAP advance time, creating a closed-loop system that adapts to changing network conditions and maintains synchronous coordination despite packet switched network variability.
Solution Approach 2:
The patent makes the MAP advance time dynamic rather than static. The CMTS adjusts the MAP advance time based on measured latency conditions, allowing the system to adapt to changing network states. This dynamic adjustment enables the system to maintain proper synchronization coordination under varying packet switched network latency conditions.
2Reliability
If MAP advance time is increased to ensure reliable transmission scheduling, then cable modems have sufficient time to receive and process scheduling messages, but excessive MAP advance time increases processing overhead and reduces user throughput
Solution Approach 1:
The patent applies partial action by adjusting the MAP advance time to be just sufficient for reliable scheduling rather than consistently using excessive advance time. The system dynamically determines the minimum necessary MAP advance time based on actual measured latency, using only the required amount of advance notification while avoiding unnecessary processing overhead and throughput reduction.
Solution Approach 2:
The patent changes the MAP advance time parameter dynamically based on measured latency conditions. Rather than using a fixed conservative value, the system adjusts this timing parameter in response to actual network conditions, optimizing the balance between reliable scheduling and maintaining high user throughput by avoiding excessive advance time adjustments.
3Reliability
If adaptive adjustment of MAP advance times is implemented based on measured latency, then reliable transmission scheduling is maintained under varying network conditions, but processing overhead increases due to continuous measurement and adjustment operations
Solution Approach 1:
The patent implements periodic measurement and adjustment of MAP advance time rather than continuous adjustment. The system measures latency at periodic intervals and adjusts the MAP advance time based on these periodic measurements, maintaining synchronization reliability while reducing processing overhead compared to continuous adaptation. This periodic approach balances reliability with acceptable processing complexity.
Data Source
AI summary
Systems and methods for dynamically adjusting a MAP advance time for a MAP message sent from a CCAP core to an RPD, based on a comparison of at least one measured latency value against at least one threshold.