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.
Study tools
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.
§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.
01SMS, end to end
How a text message travels: submit, route, deliver, report. Encodings, SMPP, receipts.
02HLR 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.
29How 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.
04SS7 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.
10Every generation: 1G to 6G
1G to 6G ladder, with GSM, GPRS, EDGE, UMTS and HSPA in detail.
114G LTE and the EPC
4G LTE and EPC: eNodeB, MME, SGW, PGW, Diameter, bearers, procedures.
125G: 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.
14Identities, numbers, SIMs and services
IMSI, MSISDN, IMEI, SIM/eSIM, numbering, services (USSD, RCS, MMS) and protocols.
20Radio engineering: propagation, link budget and network planning
Decibels, path loss, link budget, Shannon, cell planning, KPIs, microwave links.
19Fixed 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.
17Satellite communications and Non-Terrestrial Networks (NTN)
GEO, MEO, LEO orbits, bands, 3GPP NTN, direct-to-cell, GNSS, satellite security.
21Public safety, railways, vehicles and emergency communications
112/eCall, TETRA, MCPTT, GSM-R/FRMCS, V2X, aviation, maritime, resilience.
Law & regulation
Security, attacks & firewalls
Security across all generations and the firewall family
Security across every generation: SS7, Diameter, GTP, SIP, SEPP and the firewall family.
25Signalling attacks in depth (and the defence for each)
Signalling attacks step by step: SS7, SCCP, ISUP, Diameter, GTP, SIP/IMS, 5G SBA, with defences.
26The firewall family: how each telecom firewall works
Every telecom firewall explained: SS7, Diameter, GTP, SMS, SBC, SEPP, NGFW; rules and operation.
27Attacks beyond signalling: messaging, radio, SIM, fraud, infrastructure, and real incidents
SMS, radio, SIM/eSIM, fraud and IT attacks, real incidents, threat models and checklists.
05The SMS firewall and the fraud landscape
SMS firewall, fraud landscape: spam, spoofing, AIT, grey routes, tracking.
06Most common cases and real incidents
Most common cases and real-world incidents and what they teach.
Practice & operations
Protocol trace lab: reading real signalling
Reading real signalling: Wireshark filters, ports, SS7, Diameter, GTP, SIP, 5G, SMPP, cause codes.
24Troubleshooting playbook and career toolkit
Symptom-to-cause playbook, alarms, job roles, learning path and mental models.