Professional Standard v2.0

Mastering the
3GPP Ecosystem

"The specifications are a contract. If you don't read the clauses correctly, the system desyncs." — This guide provides the hands-on mental models for implementation engineers.

01. The Cartography

Ownership Matrix: Who writes the rules?

RAN1

Physical Layer

38.2xx

Modulation, coding, waveforms. The 'Bit-Level' masters.

RAN2

L2 & L3 Protocols

38.3xx

MAC, RRC, PDCP. The 'Logic & Signaling' masters.

RAN3

Network Interfaces

38.4xx

Xn, NG, F1. The 'Infrastructure' masters.

SA2

System Architecture

23.xxx

Core network, PDU sessions, network slices.

02. Spec Maturity Stages

Stage 1

Service Concepts

The high-level requirements. 'The system SHALL support 1ms latency'. Non-technical business logic.

TS 22.xxx

Stage 2

Architecture & Logic

Functional entities and signaling flows. State machines are defined here, but not the bit-patterns.

TS 23.501 / 38.300

Stage 3

Protocol Details

Implementation-level detail. ASN.1 syntax, message structures, and exact field semantic checks.

TS 38.331 / 38.214

03. Professional Decoder

Understanding ASN.1 Presence & Implementation Behavior

Modal Verb Intensity Map

SHALL / SHALL NOT

100% Force

Mandatory compliance. Hard failure for certification if violated.

SHOULD / SHOULD NOT

70% Force

Highly recommended. Industry standard, but exceptions allowed with proof.

MAY / OPTIONAL

40% Force

Permitted behavior. Implementation choice.

FFS

10% Force

For Further Study. Draft phase. DO NOT code proprietary logic.

04. The Anchor Technique

Rule #1: The Section Trace

Never implement from **Section 6** (ASN.1) without reading **Section 5** (Procedural Text). ASN.1 tells you the bit-field name, but Section 5 defines the **state machine behavior** and what happens if a timer expires.

The CR History Hack

Specifications are ambiguous. If a clause is confusing, scroll to the **History table** at the end. Check for **Category F** (Essential Correction) Change Requests applied in the last 6 months.

Cat F: Essential

Cat A: Release Fix

Version
Logic

V15.3.0

Release version (normative)

Logic Change (Technical)

Avoid implementing anything with V0.x.y — it is an internal working draft with zero legal weight in certification.

Case Study: Hands-On Walkthrough

Implementing
Random Access

The "Golden Thread" trace: How one feature moves through the specification waterfall.

The Anchor (Stage 2)

Protocol Logic

TS 38.300 Section 9.2

Observe the high-level handshake: Msg1 -> Msg2 -> Msg3 -> Msg4. Identify the 'Why'. We need a preamble for contention-based access.

Implementation Checklist Item #1

The Structure (Stage 3)

RRC ASN.1

TS 38.331 IE: RACH-ConfigCommon

Search within SIB1. Identify 'prach-ConfigurationIndex'. This is the configuration IE provided by the network to the UE.

Implementation Checklist Item #2

The Procedure (Stage 3)

MAC Behavior

TS 38.321 Section 5.1

The MAC State Machine. Defines when to trigger Msg1, how to handle the Random Access Response (RAR) window, and preamble power ramping.

Implementation Checklist Item #3

The Waveform (Stage 3)

PHY Processing

TS 38.213 Section 6.1

Translate index 'X' into the exact subframe and PRB (Physical Resource Block). The bit-level DSP instruction for antenna transmission.

Implementation Checklist Item #4

The "Ellipsis" Hack

When reading ASN.1, any IE ending with **`...`** (Ellipsis) is an extension marker. This is where Release 16, 17, and 18 fields are appended to Release 15 structures. If you miss this, you'll miss the latest feature improvements.

Common Mistake #1

Ignoring **Need R** inside a handover. If the network doesn't include an IE with Need R, and you don't release it, your UE will maintain the old configuration, leading to a handover failure.

Mastering the 3GPP Ecosystem