Description
For Further Specification (FFS) is a fundamental administrative and procedural notation within 3GPP Technical Specifications (TS) and Technical Reports (TR). It is not a network function, protocol, or interface, but a tag used by specification writers. When a working group encounters a technical aspect that requires more study, awaits implementation feedback, or is dependent on a decision in another group, they mark it as FFS. This explicitly signals that the current text is incomplete and the detail is intentionally left open.
The use of FFS is governed by 3GPP's specification drafting rules. It is typically applied to parameters, procedures, message fields, algorithms, or even entire functional descriptions. The presence of FFS creates an open issue or "placeholder" that must be resolved before the specification can reach a stable, implementable state. Resolving an FFS item involves technical discussion, consensus-building within the relevant working group, and ultimately the agreement on specific text to replace the FFS marker. This text is then incorporated into a later version of the same specification or, in some cases, a different, referenced specification.
From an architectural and implementation perspective, FFS has a significant impact. Equipment vendors and network operators reading a specification must identify all FFS markers to understand the gaps and risks in the technology. An FFS on a critical parameter can delay product development or lead to interim proprietary solutions. The process of resolving FFS items is a core part of the iterative standardization workflow, ensuring that specifications mature from high-level frameworks to detailed, unambiguous blueprints for interoperable equipment. Its use spans all 3GPP domains, from radio access (e.g., 36-series specs) to core network (29-series) and security (33-series), as indicated by its appearance in dozens of specification documents across releases.
Purpose & Motivation
FFS exists to enable the pragmatic and parallel development of complex telecommunications standards. 3GPP specifications are created by multiple working groups simultaneously, covering different system parts (radio, core, protocols, testing). It is impossible to finalize every minute detail in a single step. FFS provides a formal mechanism to advance the overall specification framework while acknowledging and tracking unresolved technical points.
This solves the problem of specification deadlock. Without FFS, work on a broad section of a spec would halt completely until every minor detail was agreed upon, drastically slowing progress. By using FFS, groups can capture architectural agreements and the majority of a procedure's flow, leaving specific values or algorithmic details for later resolution based on simulation results, implementation experience, or harmonization with other groups. It directly addresses the challenge of managing the interdependence between different parts of a large, system-wide standard. Historically, this notation has been essential from the first 3GPP releases (R99) onwards, allowing the rapid development of foundational specs like the RRC protocol (25.331) while leaving certain parameters for later refinement.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (39 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the "FFS" (For Further Specification) function was addressed through specific actions to resolve and clean up pending items. This included removing the FFS designation for location information in the RRC protocol specification (TS 38.331) and performing a general cleanup of references to Layer 1 specifications. Furthermore, the release introduced further enhancements for existing technologies like CoMP and NB-IoT, moving them from FFS status to concretely specified features.
- Introduction of further enhancements to CoMP TS 36.331CR3251
- Introduction of further NB-IoT enhancements other than EDT in TS 36.331 TS 36.331CR3333
- Correct Kseaf and Kausf length in EF5GAUTHKEYS to align with SA3 specification TS 31.102CR0810
- Cleanup of references to L1 specifications TS 38.331CR0694
- CR to 38.331 on removing FFS of locationInfo TS 38.331CR0783
- Further update of Need codes TS 38.331CR0866
+ 1 more changes
In Release 16, the "For Further Specification" function was updated to introduce "Even further Mobility enhancement in E-UTRAN," which included defining corresponding UE capabilities for this LTE enhancement. This built upon the previous mobility further enhancement work with specific technical corrections to refine the feature set.
In Release 17, the "FFS" function saw updates focused on corrections and alignment for Multi-RAT Dual Connectivity (MR-DC) enhancements, as indicated by multiple Change Requests. These included technical corrections to MR-DC procedures and an alignment of NPRACH preamble descriptions for IoT-NTN parameters with the RAN1 specification. Additionally, a further correction was made to the RRC specification concerning 71 GHz operation on multi-PUSCH.
- Introduction of further multi-RAT dual-connectivity enhancements TS 36.331CR4774
- Introduction of further multi-RAT dual-connectivity enhancements TS 38.331CR2954
- Corrections for further MRDC enhancements TS 36.331CR4813
- Corrections for further MR-DC enhancements TS 36.331CR4867
- Alignment of NPRACH preamble descriptions with RAN1 specification for IoT-NTN parameters TS 36.331CR4930
- Corrections for further MRDC enhancements TS 38.331CR3137
+ 4 more changes
In Release 18, the FFS function saw its scope expanded to include further enhancements in three key areas: NR coverage, NR mobility, and measurement gaps. These were accompanied by the addition of corresponding Protocol Implementation Conformance Statement (PICS) proformas to formally specify testing requirements for these new enhancements. Furthermore, corrections and updates were applied to the specifications for sidelink RRC and sidelink relay RRC to align with these developments.
- Introduction of further measurement gap enhancements TS 38.331CR4063
- Introduction of Further NR coverage enhancements in RRC TS 38.331CR4433
- Introduction of further NR mobility enhancements TS 38.331CR4458
- Alignment to latest ETSI SET specifications TS 31.102CR1038
- Correction on further measurement gap enhancements TS 38.331CR4586
- Miscellaneous corrections on further mobility enhancements in NR TS 38.331CR4606
+ 12 more changes
In Release 19, the primary new development for the "For Further Specification" function was the provision of further corrections to the Non-Terrestrial Networks (NTN) Phase 3 specifications. This work focused on refining and stabilizing the detailed technical procedures and capabilities for NR NTN that were initially outlined for finalization in this release. The corrections ensured the specifications were complete and interoperable for this advanced network feature.
- Further corrections to NR NTN Phase 3 TS 38.331CR5627
Explore further
Broader topics and technologies where FFS plays a role.
Defining Specifications
3GPP specifications that define or reference FFS, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 21.111 vj00 | USIM and UICC Requirements for 3G | Rel-19 |
| TS 21.810 v1300 | Multi-mode UE Issues - Categories, principles and procedures | Rel-4 |
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TR 21.910 v1300 | Multi-mode UE Operation Principles | Rel-4 |
| TS 22.057 vj00 | Mobile Execution Environment (MExE) Stage 1 | Rel-19 |
| TS 22.060 vj00 | GPRS Stage 1 Service Description | Rel-19 |
| TS 22.112 v1800 | USAT Gateway System Specification | Rel-8 |
| TS 22.121 v1400 | Virtual Home Environment Requirements | Rel-5 |
| TS 22.822 vg00 | Satellite Access in 5G Study | Rel-16 |
| TS 23.110 vj00 | Access Stratum Services Specification | Rel-19 |
| TS 23.240 vj00 | 3GPP Generic User Profile (GUP) Architecture | Rel-19 |
| TR 23.923 v1300 | Mobile IP+ Feasibility Study for UMTS/GPRS | Rel-4 |
| TS 25.106 vj00 | UTRA FDD Repeater RF Performance Requirements | Rel-19 |
| TS 25.143 vj00 | UTRA FDD Repeater RF Test Requirements | Rel-19 |
| TS 25.153 vj00 | LCR TDD Repeater RF Requirements & Testing | Rel-19 |
| TS 25.331 vj00 | UTRAN RRC Protocol Specification | Rel-19 |
| TS 25.346 vj00 | MBMS in UTRA Technical Specification | Rel-19 |
| TS 25.401 vj00 | UTRAN Overall Architecture | Rel-19 |
| TS 25.420 vj00 | Iur Interface Introduction for UTRAN | Rel-19 |
| TR 25.931 vj00 | UTRAN Signalling Procedures Examples | Rel-19 |
| TS 26.116 vj00 | TV Video Formats for 3GPP Services | Rel-19 |
| TS 26.265 vj10 | Video Operation Points & Capabilities | Rel-19 |
| TS 26.802 vj20 | Multicast Enhancements for 5G Media Streaming | Rel-19 |
| TR 26.806 vi00 | Technical Report on Smartly Tethering AR Glasses | Rel-18 |
| TR 26.862 vh00 | Immersive Teleconferencing & Telepresence for Remote Terminals | Rel-17 |
| TR 26.925 vj00 | Media Traffic Characteristics for 3GPP Networks | Rel-19 |
| TR 26.926 vj00 | Traffic Models & Quality Evaluation for Media/XR in 5G | Rel-19 |
| TR 26.928 vj00 | Study on eXtended Reality (XR) in 5G | Rel-19 |
| TR 26.998 vj00 | 5G AR/MR Glasses Integration Study | Rel-19 |
| TS 28.820 vc00 | Umbrella Operation Model for Fixed Mobile Convergence | Rel-12 |
| TS 29.060 vj00 | GPRS Tunnelling Protocol (GTP) version 1 | Rel-19 |
| TS 29.332 vj00 | MGCF-IM-MGW Interface Protocol (Mn) | Rel-19 |
| TS 29.415 vj00 | Nb User Plane Protocol Specification | Rel-19 |
| TS 29.424 v801 | H.248 Profile for Trunking Media Gateways | Rel-8 |
| TS 31.102 vj40 | USIM Application Specification | Rel-19 |
| TS 31.103 vj00 | ISIM Application Specification | Rel-19 |
| TS 31.213 vi30 | Test specification for (U)SIM | Rel-18 |
| TS 32.101 vj00 | Management principles and high-level requirements | Rel-19 |
| TS 32.582 vj00 | HNB Management Information Model for Type 1 Interface | Rel-19 |
| TS 32.584 vj00 | HNB OAM&P XML Definitions for Type 1 Interface | Rel-19 |
| TS 32.592 vj00 | HeNB OAM&P Information Model | Rel-19 |
| TS 32.594 vj00 | Data definitions for HeNB to HeMS Type 1 interface | Rel-19 |
| TS 32.816 v800 | UMTS Management Reuse for E-UTRAN/EPC | Rel-8 |
| TS 32.818 v800 | SA5 MTOSI XML Harmonization Study | Rel-8 |
| TS 32.821 v1900 | SON OAM Architecture for Home NodeB | Rel-9 |
| TS 32.826 va00 | Study on Energy Savings Management in LTE/SAE Networks | Rel-10 |
| TS 32.842 vd10 | Management of Virtualized 3GPP Core Networks | Rel-13 |
| TS 36.143 vj00 | E-UTRA FDD Repeater RF Testing | Rel-19 |
| TS 36.331 vj00 | LTE RRC Protocol Specification | Rel-19 |
| TS 36.523 vj00 | UE Conformance Test Spec for Idle Mode | Rel-19 |
| TS 36.579 | 3GPP TR 36.579 | R99 |
| TR 36.927 vj00 | Network Energy Saving for E-UTRAN | Rel-19 |
| TS 37.571 vj00 | UE Conformance for Positioning | Rel-19 |
| TS 37.579 vi40 | Mission Critical services conformance testing | Rel-18 |
| TR 37.901 vf10 | UE Application Layer Data Throughput Performance | Rel-15 |
| TS 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |
| TS 38.508 vj11 | 5G NR UE Radio Transmission & Reception | Rel-19 |
| TS 38.509 vi00 | Special conformance testing functions for UE | Rel-18 |
| TS 38.523 vj20 | 5G NR UE Conformance Testing: Idle/Inactive | Rel-19 |
| TR 38.903 vj00 | Test Tolerances & Measurement Uncertainties | Rel-19 |
| TR 43.901 vj00 | Generic Access to A/Gb Interface Feasibility Study | Rel-19 |
| TS 51.010 vj00 | SIM Application Toolkit Conformance Testing | Rel-19 |
| TS 51.013 vj00 | SIM API for Java Card Test Specification | Rel-19 |