Rate Adaptation of CBR Data Over Metro Transport Networks
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Solution Overview
Problem
The transmission of constant bit rate (CBR) client signals over Metro Transport Networks (MTN) faces challenges due to differences in clock domains between intermediate nodes, leading to issues with maintaining a constant number of server layer bits per Generic Mapping Procedure (GMP) window, increased overhead bandwidth, and latency caused by packet processing.
Innovation Solution
The method involves incorporating GMP overhead into the CBR client data stream at the source node, using pseudo-Ethernet packets to map encoded blocks of CBR client data, inserting variable idle blocks, and aligning the MTN path overhead with GMP frames to generate rate-adapted GMP frames, which are then transmitted and adapted at intermediate nodes to maintain clock synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If GMP overhead is placed in the server layer channel, then rate adaptation can be performed, but the MTN server channel lacks GMP overhead and requires section layer overhead processing at each node
Solution Approach 1:
The patent introduces an intermediary mechanism by placing GMP overhead in the path layer rather than the server layer, allowing rate adaptation information to be carried without requiring section layer overhead processing at intermediate nodes. This intermediary positioning resolves the conflict between needing rate adaptation and avoiding complex node processing.
Solution Approach 2:
The patent moves the GMP overhead from the traditional server layer dimension to the path layer dimension, creating a new structural arrangement that bypasses the limitation of the MTN server channel lacking GMP overhead while avoiding the complexity of section layer processing.
2Adaptability or versatility
If packet domain methods are used to accommodate clock domain differences, then transmission can proceed, but large overhead bandwidth and latency are required
Solution Approach 1:
The patent extracts the rate adaptation function from the packet domain and implements it directly in the GMP overhead within the path layer. This extraction eliminates the need for packet encapsulation overhead while maintaining clock domain accommodation capabilities through the GMP mechanism.
3Adaptability or versatility
If packet processing is used to accommodate clock domain differences, then transmission can proceed, but significant complexity is added to deriving client signal rate
Solution Approach 1:
The patent introduces GMP overhead as an intermediary that carries rate adaptation information directly in the path layer, eliminating the need for complex packet processing and timestamp analysis. The GMP mechanism provides a straightforward method for deriving client signal rate without the complexity of packet domain operations.
4Adaptability or versatility
If regular Ethernet packet encapsulation is used, then clock domain differences can be accommodated, but undesirable latency is introduced
Solution Approach 1:
The patent extracts the essential rate adaptation function from the packet encapsulation process and implements it directly in the GMP overhead. This extraction eliminates the need for full packet encapsulation and de-encapsulation operations, thereby reducing transmission latency while maintaining clock domain accommodation.
Data Source
AI summary
A system and method for performing rate adaptation of constant bit rate (CBR) client data for transmission over a Metro Transport Network (MTN) by defining a plurality of pseudo-Ethernet packets at a source node, assembling a plurality of Generic Mapping Procedure (GMP) frames by mapping a plurality of blocks from a stream of encoded blocks of CBR client data, a plurality of pad blocks, and GMP overhead into consecutive pseudo-Ethernet packets of the plurality of pseudo-Ethernet packets, inserting a variable number of idle blocks between one or more of the consecutive pseudo-Ethernet packets and inserting an MTN path overhead (POH) frame that is aligned to the plurality of GMP frames to generate a plurality of rate adapted GMP frames for transmission over the MTN to an intermediate node or a sink node.