The Pocket Siren test network
The pilot network combines high-power main transmitters (HPHT, High Power High Tower) with lower-power gap fillers (LPLT). This makes it possible to test both wide rural coverage and reception in cities and inside buildings. The network complies with ETSI TS 103 720.
Five transmitters, two frequencies
| Site | Type | Height | Channel | Transmitter power | ERP | Role |
|---|---|---|---|---|---|---|
| Tallinn TV Tower | HPHT | 270 m | E40 · 626 MHz | 3 kW | 40 dBW | Main transmitter for northern Estonia |
| Koeru | HPHT | 337 m | E41 · 634 MHz | 3 kW | 39.3 dBW | Central Estonia, SFN with Pärnu |
| Pärnu | HPHT | 187 m | E41 · 634 MHz | 3 kW | 42.6 dBW | South-west Estonia, SFN with Koeru |
| Tallinn, Kristiina | LPLT | 97 m | E40 | 600 W | 29 dBW | City coverage, SFN with the TV Tower |
| Järvakandi | LPLT | 78 m | E41 | 600 W | 30 dBW | Area between Tallinn and Pärnu |
SFN: one frequency, several masts
Koeru, Pärnu and Järvakandi send the same signal on the same channel (E41), and the phone combines their signals. This covers a large area without spending more spectrum, but the transmitters must be precisely synchronised via GNSS.
MFN: different frequencies side by side
Tallinn runs on a separate channel (E40). This lets us study how areas on different frequencies work together and how a moving phone hands over from one transmitter to another.
System overview
NAKOLOS core (Big Blue Marble)
Receives CAP alerts automatically, manages TV and radio streams, and controls and monitors the network centrally. It is technically ready for device-based geofencing (WEA 3.0 DBGF).
TRedess Fourth Series
Energy-efficient transmitters suited to both high- and low-power use. Transmitter-side MER is above 40 dB, a good starting point for both public warning and media.
Measurement equipment
Gsertel Hexylon 5G, Rohde & Schwarz FSP and FSH, Kathrein MSK200, and test phones logging with NetMonster. Measurements were made outdoors, indoors and in moving cars.
Which phones worked in the tests
The tests used 40 5G Broadcast phones showing TV and video and more than 40 n71-capable phones showing alerts. The signal is received by Android phones with a Qualcomm chip and FeMBMS support enabled by the manufacturer.
| Device | Chipset | Live TV | National alert (4370) in silent mode | Device-based geofencing (4400) |
|---|---|---|---|---|
| Xiaomi 13 | Snapdragon 8 Gen 2 | Yes | Yes | No |
| OnePlus 10T 5G | Snapdragon 8+ Gen 1 | Yes | Hardware mute switch decides | No |
| OnePlus 10 Pro 5G | Snapdragon 8 Gen 1 | Yes | Yes | No |
| Motorola Edge 50 Ultra | Snapdragon 8s Gen 3 | Yes | Yes | No |
| Motorola Razr 50 Ultra | Snapdragon 8s Gen 3 | Yes | Yes | No |
| Motorola Razr+ 2023 | Snapdragon 8+ Gen 1 | Yes | Yes | No |
| Nothing Phone (3) | Snapdragon 8s Gen 4 | Yes | Yes | No |
| OnePlus 13R | Snapdragon 8 Gen 3 | Yes | Yes | No |
| Motorola Edge 50 Fusion | Snapdragon 7s Gen 2 | – | Yes | No |
| Samsung Galaxy S25+ (US) | Snapdragon 8 Elite | – | Yes | No |
| Apple iPhone 13 (US) | Apple A15 | No | No (no Apple entitlement) | No |
“–” means this was not assessed in the tests. All other alert levels (4371–4380) follow the phone’s sound profile.
iPhone
A US-model iPhone 13 finds the network, but the connection drops after a few seconds. Apple allows emergency alerts only for operators it has an agreement with. The Ministry of the Interior and Levira asked Apple for test access, and Apple replied that this is not possible during the Estonian test period.
Device-based geofencing
The newer WEA 3.0 geofencing feature (category 4400) did not work on any tested phone sold in Europe. The core sends these alerts correctly, but phone firmware lacks support. Testing with Qualcomm research devices (CRD) was outside the scope of the pilot.