OTN GMP Overhead Encoding via Inversion Patterns and CRC
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Solution Overview
Problem
Existing methods for encoding and controlling count value information in Optical Transport Networks (OTNs) face challenges such as limited overhead bits, complexity in error correction, and inefficiencies in handling changes in count values, particularly in scenarios with burst errors and non-integer client signal and OTN payload byte rate ratios.
Innovation Solution
A method that determines a count value change within a predetermined range, selects an inversion pattern, calculates a cyclic redundancy check (CRC) code, and inserts these into the Generic Mapping Procedure (GMP) overhead of the OTN signal frame, using bit inversion to indicate increments or decrements, and employing CRC for error detection and validation to ensure robustness and efficient communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inversion pattern with CRC code is used for count value encoding, then error detection and robustness are improved, but overhead bits are consumed and device complexity increases
Solution Approach 1:
The count value is encoded using inversion patterns that are segmented into specific bit positions within the GMP overhead bytes. The CRC code is separately calculated and placed in a dedicated byte (JC3), allowing error detection without requiring complex encoding of every individual bit. This segmentation reduces the complexity burden while maintaining robustness.
Solution Approach 2:
The CRC code acts as an intermediary mechanism between the inversion pattern encoding and the received data. Instead of complex error correction coding, the system uses a simpler CRC verification that mediates between the encoded count value and the receiver's interpretation, providing reliable error detection with minimal complexity overhead.
2Speed
If count value changes are handled with predetermined range checking, then synchronization speed is improved, but handling complexity for non-integer rate ratios increases
Solution Approach 1:
The system changes the parameter representation by using inversion patterns to indicate count value changes within a predetermined range (±1 or ±2). This transforms the handling of non-integer rate ratios into a simpler matter of detecting which inversion pattern was used, rather than dealing with complex fractional adjustments. The receiver can rapidly determine the intended change by identifying the inversion pattern, enabling fast synchronization even with non-integer client signal and OTN payload byte rate ratios.
3Reliability
If CRC code is inserted in GMP overhead, then error detection is improved, but available overhead bits for count value information are reduced
Solution Approach 1:
The GMP overhead is segmented into functional components: JC1 and JC2 bytes contain the inversion pattern information for count value changes, while JC3 byte is dedicated to the CRC code. This segmentation allows the system to maintain full count value information capacity in the first two bytes while adding error detection capability in the third byte, minimizing the impact on information transmission.
Solution Approach 2:
Instead of reducing the count value field size to accommodate CRC, the system uses inversion patterns of existing count value bits to encode change information. The actual count value is transmitted unchanged in the payload, while only the inversion pattern (indicating +1, -1, or +2/-2 changes) is encoded in the overhead. This approach preserves full count value information capacity while adding CRC for error detection.
Data Source
AI summary
A method of communicating count value information in an Optical Transport Network (OTN) signal frame. The method comprises determining a count value indicating a number of payload bytes to be sent in a next OTN signal frame; determining that a change in the count value (Δ) with respect to a current count value is within a predetermined range; selecting an inversion pattern indicating the change in the count value; determining a cyclic redundancy check (CRC) code associated with the inversion pattern; and, inserting the inversion pattern and the CRC code in a Generic Mapping Procedure (GMP) overhead of the OTN signal frame.