Telecom study guide

From antennas to the core: 2G, 3G, 4G and 5G, voice and SMS, SS7 and signalling, security and fraud, every acronym explained. Read a module, then test yourself.

38 modules610 acronyms693 quiz questionsflashcards

Start with Module 0 → Take a quiz

Study tools

A–Z

Acronym glossary

Every acronym with its full name and meaning. Search and filter by topic.

⟲

Flashcards

Flip cards: acronyms and key concepts. Mark what you know, repeat the rest.

Quizzes

Multiple-choice quizzes by topic with explanations and score tracking.

⚙

Calculators & lookup

Code lookup, dB, link budget, Shannon, Erlang, SMS segments, number normaliser, IMSI splitter.

References

Standards, RFCs, GSMA documents, books and reports behind this guide.

Foundations

How a mobile network works (the big picture)

The big picture: radio, core, signalling, the building blocks of every mobile network.

SMS, end to end

How a text message travels: submit, route, deliver, report. Encodings, SMPP, receipts.

HLR and VLR

The subscriber databases and how the network always knows where you are.

How it works: processes

How it really works: network procedures step by step

Step-by-step stories: LTE attach, 5G registration, calls, VoLTE, handover, roaming, SMS, data, 112.

How it really works: business, service and operational processes

Business processes: SIM provisioning, porting, SIM swap, charging, billing, incidents, change, builds, LI.

Signalling (SS7)

SS7 introduction (the plain-words story)

SS7 explained in plain words: what it is, who uses it, why it matters.

SS7 deep dive (fields and protocols)

SS7 deep dive: MTP, SCCP, TCAP, MAP, ISUP, SIGTRAN, fields and flows.

Voice & generations

Voice calls, from 2G circuit to VoLTE and VoNR

Calls from circuit to VoLTE/VoNR: ISUP, SIP, IMS, codecs, charging, fixes.

Every generation: 1G to 6G

1G to 6G ladder, with GSM, GPRS, EDGE, UMTS and HSPA in detail.

4G LTE and the EPC

4G LTE and EPC: eNodeB, MME, SGW, PGW, Diameter, bearers, procedures.

5G: New Radio and the service-based core

5G NR and the service-based core: slices, SA/NSA, Open RAN, SUCI, SEPP.

Radio, transport, numbers

Radio, spectrum and transport (how bits actually travel)

Spectrum, modulation, cells, backhaul, MPLS/IP, OSS/BSS and business terms.

Identities, numbers, SIMs and services

IMSI, MSISDN, IMEI, SIM/eSIM, numbering, services (USSD, RCS, MMS) and protocols.

Phone numbers: formats, plans and validation

E.164, formats and trunk prefixes, country table, shared codes, number types, TON/NPI, six validation levels, storage rules.

Radio engineering: propagation, link budget and network planning

Decibels, path loss, link budget, Shannon, cell planning, KPIs, microwave links.

Fixed access, optical and enterprise networks

DSL, cable, GPON/FTTH, DWDM, MPLS, SD-WAN, Ethernet/IP essentials, telco cloud.

Wireless beyond cellular

Wi-Fi, Bluetooth, short-range and low-power wide-area networks

Wi-Fi 4 to 7, Bluetooth, NFC, UWB, Zigbee, LoRa, NB-IoT and IoT protocols.

Satellite communications and Non-Terrestrial Networks (NTN)

GEO, MEO, LEO orbits, bands, 3GPP NTN, direct-to-cell, GNSS, satellite security.

Public safety, railways, vehicles and emergency communications

112/eCall, TETRA, MCPTT, GSM-R/FRMCS, V2X, aviation, maritime, resilience.

Law, regulation & industry

Regulation, law and the Croatian market

ITU, EU law, GDPR, roaming, spectrum, numbering, and the Croatian market.

The industry: who is who in telecom, and how money flows

Who is who: operators, MVNOs, towers, vendors, carriers, IPX, clearing, aggregators, GT leasing, and how money flows.

Markets: Croatia, its neighbours and the EU

Croatia in depth (HAKOM Q1 2026), neighbours (SI, BA, RS, ME, HU, AT, IT), owners across the region, EU picture.

Global markets: the biggest countries and the other regions

Global markets: China, India, USA, Indonesia, Brazil, Mexico, Japan/Korea, DE/UK/FR, Turkey, Gulf, Africa, Australia.

More markets: the rest of Europe, Asia, Africa and the Americas

More markets: Spain, Poland, Nordics, Benelux/CH, SE Europe, Russia, Ukraine, Pakistan, Bangladesh, Vietnam, Kenya, Egypt, Canada, NZ.

History and trends: where telecom came from and where it is going

History timeline (1876–2026) and trends: switch-offs, 6G, network APIs, RCS E2EE, post-quantum, AI, consolidation.

Security, attacks & firewalls

Security across all generations and the firewall family

Security across every generation: SS7, Diameter, GTP, SIP, SEPP and the firewall family.

Signalling attacks in depth (and the defence for each)

Signalling attacks step by step: SS7, SCCP, ISUP, Diameter, GTP, SIP/IMS, 5G SBA, with defences.

The firewall family: how each telecom firewall works

Every telecom firewall explained: SS7, Diameter, GTP, SMS, SBC, SEPP, NGFW; rules and operation.

Attacks beyond signalling: messaging, radio, SIM, fraud, infrastructure, and real incidents

SMS, radio, SIM/eSIM, fraud and IT attacks, real incidents, threat models and checklists.

The SMS firewall and the fraud landscape

SMS firewall, fraud landscape: spam, spoofing, AIT, grey routes, tracking.

Most common cases and real incidents

Most common cases and real-world incidents and what they teach.