Description
Do Not Use (DNU) is a designation applied within 3GPP technical specifications to flag certain parameters, information elements, or values as deprecated, reserved for future use, or erroneous. Its primary appearance is in TS 38.305, which defines the stage 2 functional specification of User Equipment (UE) positioning in NG-RAN. In this context, DNU may be applied to specific positioning methods, measurement types, or signaling parameters that are no longer recommended for implementation or that were incorrectly defined in earlier releases. The marker instructs implementers to avoid using the flagged item in new deployments or designs, though it may still be present in the specification to ensure backward compatibility with existing systems or to prevent reuse of the identifier for a different purpose. The specification typically clarifies the reason for the DNU designation, such as replacement by a superior method, discovery of technical flaws, or alignment with updated architectural principles. From a protocol perspective, a network element or UE receiving a message containing a DNU-marked parameter should either ignore it, treat it as an error, or apply a defined fallback behavior as specified. The handling of DNU elements is crucial for interoperability, as it prevents the propagation of deprecated features into new network implementations while allowing legacy equipment to continue operating. The 3GPP standardization process uses DNU as a tool for managing the evolution of protocols, ensuring that the specification remains clean and unambiguous over multiple releases.
Purpose & Motivation
The DNU marker was created to address the challenge of managing protocol evolution and maintaining specification clarity over multiple 3GPP releases. As mobile standards evolve, certain features, parameters, or measurement methods become obsolete due to technological advancements, are found to be technically flawed, or are superseded by more efficient alternatives. Simply removing these elements from specifications could break backward compatibility and cause interoperability issues with legacy equipment already deployed in the field. The DNU designation provides a formal mechanism to deprecate such elements without physically deleting them, signaling to implementers that they should not be used in new developments. This helps prevent the perpetuation of outdated or incorrect implementations, reduces testing complexity, and guides the industry towards recommended practices. It is particularly important in complex areas like positioning, where multiple methods coexist and precision is critical. By marking elements as DNU, 3GPP ensures that the specification remains a reliable reference while accommodating the natural lifecycle of protocol features.
Key Features
- Marks specific parameters, information elements, or values within 3GPP specs as deprecated or reserved
- Primarily documented in TS 38.305 for NG-RAN UE positioning parameters
- Instructs implementers to avoid using the flagged item in new designs or deployments
- Maintains backward compatibility by retaining the element in the specification
- Prevents reuse of identifiers for conflicting purposes in future releases
- Clarifies protocol evolution by formally indicating obsolete features
Evolution Across Releases
Introduced the DNU marker within 3GPP specifications, specifically in TS 38.305 for NG-RAN positioning. It was defined to formally deprecate certain positioning-related parameters or methods that were deemed obsolete, incorrect, or replaced by enhanced alternatives, ensuring implementer guidance while preserving protocol structure.
Defining Specifications
| Specification | Title |
|---|---|
| TS 38.305 | 3GPP TR 38.305 |