OTN Tributary Mapping for Transparent Sub-Wavelength Transmission
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Solution Overview
Problem
Current technologies, such as SONET, fail to transparently transmit client signals that follow the SONET protocol while maintaining timing integrity, especially for sub-wavelength channels, and cannot provide quality of service monitoring without delving into the client's signal.
Innovation Solution
The Digital Wrapper standard is extended to create a tributary group from OTU1 frames, which are mapped onto 64 OTN tributary frames with di-byte interleaving, allowing for synchronization and phase-offset measurement to maintain high clock fidelity, and modified pointer processing is used to minimize jitter and wander.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SONET encapsulates client signals into SPE blocks and injects them into SONET frames, then the provider can monitor quality of service, but the client signal timing integrity is lost and transparent transmission is not achieved
Solution Approach 1:
The patent introduces an intermediary mapping structure where client signals are mapped into the payload area of OTN frames without being encapsulated in traditional SONET SPE blocks. This intermediary mapping layer preserves the original client signal timing while allowing the provider to monitor quality of service through overhead bytes in the OTN frame structure, thus resolving the contradiction between monitoring capability and timing integrity.
Solution Approach 2:
The patent segments the frame structure into distinct areas: overhead area for provider monitoring and payload area for client signal transmission. By separating these functions into different segments of the frame structure, the system can simultaneously achieve quality of service monitoring through overhead bytes and preserve client signal timing integrity through direct payload mapping.
2Reliability
If the provider uses a particular protocol to transmit client signals, then quality of service can be monitored, but the provider cannot transmit client signals that follow the same protocol transparently
Solution Approach 1:
The patent creates a universal mapping mechanism that can handle multiple client protocols simultaneously. The OTN frame structure with its standardized payload area can accommodate various client signals (including SONET, SDH, Ethernet, etc.) without requiring protocol-specific encapsulation, thus achieving both quality of service monitoring and protocol transparency through a single unified structure.
Solution Approach 2:
The intermediary mapping structure acts as a protocol-agnostic layer between the provider's transmission infrastructure and diverse client protocols. This intermediary layer preserves the original client protocol characteristics while enabling provider monitoring capabilities, allowing transparent transmission of client signals regardless of their protocol type.
3Productivity
If SONET multiplexes multiple signals onto a fiber, then bandwidth efficiency is improved, but sub-wavelength channels cannot be transmitted transparently
Solution Approach 1:
The patent transitions from traditional time-division multiplexing in the time domain to a frame-based structure with distinct overhead and payload areas in the spatial dimension. This dimensional change allows multiple sub-wavelength channels to be mapped into payload areas while overhead bytes in the overhead area provide timing and monitoring information, achieving both bandwidth efficiency and timing fidelity simultaneously.
Solution Approach 2:
The frame structure is segmented into overhead area for timing and monitoring functions, and payload area for client signal transmission. This segmentation allows the system to efficiently multiplex multiple sub-wavelength channels in the payload area while preserving timing information through the overhead area, thus achieving both bandwidth efficiency and timing fidelity.
4Ease of operation
If the provider add/drop multiplexes channels without extracting all other channels, then network flexibility is improved, but timing synchronization across channels becomes difficult
Solution Approach 1:
The frame structure segments timing information into the overhead area, separate from the payload area where client signals are transmitted. This segmentation allows individual channels to be added or dropped at intermediate nodes by modifying only their specific payload and overhead portions, while the overall frame timing structure remains synchronized across all channels, thus achieving both network flexibility and timing synchronization.
Solution Approach 2:
The overhead area acts as an intermediary layer that carries timing and synchronization information independent of the payload content. This intermediary overhead structure enables intermediate nodes to perform add/drop operations on specific channels without disrupting the timing synchronization of other channels, as the overhead timing information can be independently managed for each channel.
Data Source
AI summary
An arrangement that allows transmission of client signals with higher clock fidelity is achieved by developing a phase offset measure at an ingress node, communicating it to the egress node, and recovering the client's clock from the received data and from the received phase-offset information. The ability to recover the client's clock with high fidelity is enhanced by adaptive pointer processing in intermediate nodes and the egress node of the network that the client's signal traverses. The adaptive pointer processing filters incoming pointers from upstream nodes and injects new positive and negative pointer justifications in excess of what is minimally necessary to allow them to be filtered by successive nodes and insure proper transmission over a network that employs a protocol involving framing layer frames embedded in communication layer frames. Illustratively, the network protocol is an extended ITU Recommendation G.709 Digital Wrapper protocol, arranged to employ frames of 15240 columns by four rows.