Some communications must work when everything else fails, or must be reserved for professionals. They use their own radio standards — which are now merging into 4G/5G.
1. Emergency calls
| Item | Facts |
|---|---|
| 112 | Single European emergency number (works in all EU countries, free, from any phone, even without SIM or credit). Also 911 (US/Canada), 999 (UK), 000 (Australia). In Croatia: 112 plus 192 police, 193 fire, 194 ambulance |
| PSAP | Public Safety Answering Point — the call centre that receives emergency calls |
| Routing | Call goes to the nearest PSAP, chosen by the cell location; network must give caller location |
| Location methods | Cell ID, AML (Advanced Mobile Location) — phone sends GNSS/Wi-Fi location by SMS/data when 112 is dialled — A-GNSS, E-CID, OTDOA; indoor is hard |
| eCall | EU rule: new car models since 2018 have an automatic 112 call after a crash with a MSD (Minimum Set of Data: position, direction, vehicle type, time). Based on 2G/3G/4G voice; NG eCall is moving to IMS/packet |
| NG112 / NG911 | IP-based emergency services (SIP, text, video, data) |
| IMS emergency (E-CSCF, LRF) | Emergency Call Session Control Function and Location Retrieval Function in IMS |
| Emergency over Wi-Fi | VoWiFi emergency calls need registered address |
| Total conversation / RTT | Accessible emergency calls (real-time text) |
| Roaming | Emergency calls are allowed without a roaming agreement (limited service state) |
| SIM-less emergency call | Phone attaches as "limited service" |
| Public warning | Cell Broadcast (CBS), EU-Alert (EU), WEA (US), ETWS (Japan), CMAS. Not SMS — one message to all phones in a cell; some countries also use location-based SMS alerts alongside it |
| Priority services | MPS / GETS / WPS (Multimedia Priority Service): priority access during congestion; ARP, UAC (Unified Access Control) |
2. Professional mobile radio (PMR) and mission-critical
| Technology | Standard | Band (Europe) | Features |
|---|---|---|---|
| TETRA | ETSI | 380–400 MHz (emergency), 410–430, 450–470 MHz | Digital trunked radio, TDMA 4 slots / 25 kHz, group calls, push-to-talk (PTT), direct mode (DMO), fast call setup < 0.3 s, encryption (TEA1–4), widely used by police, fire, ambulance and transport |
| TETRAPOL | Matra/Airbus | 380–400 MHz | French-origin trunked system (used in France, Switzerland) |
| DMR | ETSI TS 102 361 | VHF/UHF | Digital Mobile Radio Tier I/II/III; low-cost professional and amateur |
| P25 (APCO-25) | TIA | 700/800 MHz | US public safety |
| PTT over cellular (PoC) | OMA | uses LTE/5G data | Push to talk apps |
| MCPTT / MCX | 3GPP Rel-13+ | on LTE/5G | Mission Critical Push-To-Talk, MCData, MCVideo; group calls, priority, pre-emption, ProSe / sidelink direct mode, IOPS (Isolated Operation) if backhaul fails |
| FirstNet (US), ESN (UK Emergency Services Network), SafeNet (Korea) | LTE (FirstNet band 14) | Public safety broadband networks | |
| Private LTE / 5G | CBRS (US), 3.8–4.2 GHz (DE), 2.3 GHz, 3.5 GHz | Dedicated campus networks | |
| Broadband PMR roadmap | TETRA/DMR for voice, LTE/5G MCX for data and video; ETSI/3GPP interworking |
3. Railways — GSM-R and FRMCS
| Item | Facts |
|---|---|
| GSM-R | Railway version of GSM, R-GSM band 876–880 / 921–925 MHz (uplink / downlink) in Europe; ETCS Level 2/3 uses it for train control (ERTMS), plus voice (driver–controller), ASCI features: VGCS (voice group call), VBS (voice broadcast), eMLPP priority |
| ERTMS / ETCS | European Rail Traffic Management System / European Train Control System — signalling and cab control |
| Radio Block Centre (RBC) | Gives movement authority to trains via GSM-R |
| FRMCS | Future Railway Mobile Communication System — successor to GSM-R, based on 3GPP 5G with MCX services and 1900–1910 MHz in the EU; adopted to replace GSM-R from the 2030s |
| Handover at 350 km/h | Railways require reliable handover at high speed — a harsh radio test |
| CBTC | Communications-Based Train Control for metros (often Wi-Fi or LTE) |
4. Aviation and maritime
| Technology | Use |
|---|---|
| VHF air band 118–137 MHz (AM) | Air–traffic voice |
| ADS-B (1090 MHz) | Aircraft broadcast position; collected by networks like OpenSky |
| ACARS / SATCOM / SwiftBroadband | Aircraft data messaging, cockpit/cabin links |
| In-flight connectivity (IFC) | Ku/Ka satellite, or ATG (air-to-ground LTE/5G towers); onboard picocell + NOPS allows phones with airplane-mode-off (EU rules allowed in-flight mobile service from 2008 (1800 MHz GSM) and later extended it to 4G/5G) |
| AIS (VHF 161.975 / 162.025 MHz) | Ships broadcast identity/position |
| GMDSS / DSC / Inmarsat / EPIRB | Maritime distress and safety |
| VHF marine band 156–174 MHz | Channel 16 distress/calling |
| LDACS, NavIC, GBAS | Future aviation systems |
5. Vehicles — V2X
| Variant | Standard | Notes |
|---|---|---|
| ITS-G5 / DSRC | IEEE 802.11p, ETSI | Wi-Fi-based vehicle communication in 5.9 GHz band; ETSI ITS messages: CAM (Cooperative Awareness), DENM (Decentralised Environmental Notification), SPaT/MAP |
| C-V2X (LTE-V2X) | 3GPP Rel-14/15 | PC5 sidelink direct and Uu via network; uses same 5.9 GHz ITS band |
| NR-V2X | 3GPP Rel-16/17 | Advanced use cases: platooning, sensor sharing, remote driving; sidelink Mode 1 (network-scheduled) and Mode 2 (autonomous) |
| V2V, V2I, V2N, V2P | Vehicle to vehicle / infrastructure / network / pedestrian | |
| Automotive SIM, eSIM | Embedded in car; TCU Telematics Control Unit | |
| OTA updates | Software over the air for cars | |
| Positioning | RTK GNSS, 5G positioning | |
| Teleoperation / remote driving | Needs low latency URLLC and uplink video | |
| Standards bodies | 5GAA (5G Automotive Association), ETSI ITS, SAE J2735 |
6. Drones (UAS) and robots
- Cellular-connected drones: need uplink and low latency; 3GPP Rel-15+ supports aerial UE features. Interference to ground UEs because the drone sees many cells.
- UTM / U-space (EU): drone traffic management; Remote ID.
- BVLOS (Beyond Visual Line of Sight) flights need cellular + satellite.
- Industrial automation: TSN (Time-Sensitive Networking) over 5G, PROFINET/OPC UA, AGV robots.
7. Critical infrastructure and resilience
| Topic | Notes |
|---|---|
| Backup power | Batteries (2–8 h), generators; fuel logistics; solar |
| Redundancy | Geo-redundant cores (active-active), dual-homed sites, ring topologies |
| National roaming in disasters | Allow phones to use any available network |
| Cell on wheels (COW) | Mobile base stations |
| Smart grid / SCADA | Utility comms; 450 MHz LTE for energy |
| Cyber / resilience laws | EU NIS2 (2022/2555), Critical Entities Resilience Directive; telecom is "essential" |
| Incidents | Submarine cable cuts, data-centre fires (e.g. OVHcloud Strasbourg, 2021), outages from misconfiguration (e.g. Facebook BGP 2021, Rogers Canada 2022, Optus Australia 2023), cyber attacks (Viasat KA-SAT 2022), space weather |
| Emergency SMS aid | Cell broadcast during floods/earthquakes |
Remember this: emergency and mission-critical networks add priority, group calls, always-available coverage and location on top of ordinary telecom. They are migrating from TETRA/GSM-R to 3GPP MCX and FRMCS, so everything you learned about 4G/5G applies there too.