CBR Client Signal Transport via Phase Offset Calculation
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Solution Overview
Problem
Existing methods for transporting Constant Bit Rate (CBR) clients over cell/packet networks face challenges such as delay variations, requirement for a common clock reference between source and sink nodes, and high complexity and cost, especially when dealing with multiple CBR clients at intermediate nodes.
Innovation Solution
A method that involves receiving data streams at intermediate nodes, calculating a PHY-scaled stream phase offset, and updating cumulative phase offset reports without requiring a common reference clock or processing new rate reports for each CBR client, using a PHY link input, clock offset circuit, demultiplexer, and multiplexer to manage CBR carrier streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the ITU GMP method is used to transport CBR clients, then a common reference clock is not required, but the complexity and cost increase significantly when handling multiple CBR clients at intermediate nodes
Solution Approach 1:
The patent extracts the rate report processing function from intermediate nodes and concentrates it at the source node. Only a single aggregated rate report is generated at the source, which is then transported through all intermediate nodes without requiring any processing at those nodes. This eliminates the complex per-client rate report processing that would otherwise be required at each intermediate node handling multiple CBR clients.
Solution Approach 2:
The patent creates a universal rate report structure that can represent multiple CBR clients in a single report. This aggregated rate report is universally accepted and processed only at the source node, while intermediate nodes simply forward it without modification. This universal approach eliminates the need for node-specific processing of individual client rate reports.
2Adaptability or versatility
If the sink node uses adaptive monitoring with FIFO buffer to control transmit PLL, then no common clock reference is needed, but the system becomes susceptible to delay variations in the transport network
Solution Approach 1:
The patent generates the rate report at the source node before transport, incorporating timing information that accounts for network delay characteristics. This preliminary generation of accurate rate information at the source eliminates the need for the sink node to perform adaptive monitoring that is vulnerable to delay variations. The rate report is prepared in advance with correct timing data, making the system reliable without requiring delay-sensitive adaptive adjustments at the sink.
3Measurement precision
If a common clock reference is required at source and sink nodes, then accurate CBR client bit rate computation is achieved, but the deployment cost of the transport network increases
Solution Approach 1:
The patent extracts the common clock reference requirement from the transport network and relocates it to only the source node. The source node generates the rate report using its local clock, and this report is transported through intermediate nodes without requiring them to have common clock references. The sink node processes this pre-generated report without needing a common clock, thus achieving accurate bit rate computation while eliminating the need for expensive common clock infrastructure across the entire network.
Solution Approach 2:
The patent introduces the rate report as an intermediary carrier that transports timing and rate information from the source to the sink without requiring a direct clock connection. This rate report acts as a mediator that conveys the necessary timing information through the transport network without requiring intermediate nodes or the sink to share a common clock reference with the source, thereby reducing deployment costs while maintaining measurement accuracy.
Data Source
AI summary
A method and apparatus in which a data stream generated by a previous network node, a cumulative phase offset report (CPOR) and a client rate report (CRR) are received. A counter accumulating a PHY-scaled stream clock (IPSCk) is sampled at a nominal sampling period (Tps) to obtain a cumulative PHY-scaled count (CPSC). A PHY-scaled stream phase offset (PSPO) is calculated that indicates phase difference between a PHY-scaled stream nominal bit count (LPSD) and an incoming PHY-scaled count delta (IPSD), where IPSD indicates CPSC increment between successive CPSC samples. The data stream is demultiplexed to obtain CBR carrier streams that include a previous network node CPOR (CPOR-P) and a previous network node CPO (CPO-P). A CPO is calculated that is a function of CPO-P and the PSPO. CPO-P is replaced with the calculated CPO. The CBR carrier streams are multiplexed into intermediate-network-node data streams that are transmitted from the intermediate-network-node.