Japan's Emergency Call and IoT Technology Requirements

The latest amendments to the TBL of the Telecommunications Services Act 2025:

The 2025 revision focuses on "Dual SIM Dual Standby Emergency Calls", "Emergency Cross-Carrier Roaming" and "IoT Security Enhancement", a total of three core sections:

Emergency call interconnection guarantee 

Background of the problem:

When a multi-SIM  mobile device uses a "data-only SIM" to make an emergency call, the  communication channel may be disconnected and the call may fail due to a mismatch between the SIM ID and the "Other SIM Location Data" stored by the device.

Revision requirements：

Device functions: If a multi-SIM  device fails to  make an emergency call using one SIM (e.g., data SIM does not have a voice contract), it needs to automatically switch to another SIM and try again.

Test method: Added multi-SIM  device emergency call test method;

Effective Date: July  1, 2025  (Some test methods have been delayed until  January 1, 2026  ).

Case Situation:

Revised Requirements:

Emergency cross-carrier  roaming Emergency JP-roaming test

Background and Objectives:

Background: The "Emergency Operator Roaming Study Group" was launched in September 2022, and a   partial report on the technical requirements for terminal equipment was submitted in December 2024.

Goal: In the event of a natural disaster or operator network failure, users can temporarily use other operators' "rescue networks" to ensure voice, data communication, and emergency calls.

Key time nodes:

• Date of enactment: May  29, 2025 ;

• Effective Date: October    1, 2025;

• Grace Period: Grace period for some provisions (technically difficult equipment) until  September  30, 2027

Article 32-24-2 has been added to the Terminal Equipment Rules).

IoT Security Enhancement 

JC-STAR is a voluntary security compliance assessment system for Internet of Things (IoT) products developed by Japan's Ministry of Economy, Trade and Industry (METI) and Information-technology Promotion Agency (IPA) starting from the 2022 fiscal year. Its labeling was officially launched in March 2025. This system aims to help enterprises demonstrate the security of their IoT products (such as cameras, routers, etc.) by formulating security standards and assessment procedures, so as to address the growing problem of IoT devices being hijacked for cyber attacks (e.g., DDoS attacks). 
In the revision of IoT device security standards under Japan's Telecommunications Business Act, the compliance standards of JC-STAR have been adopted as an important reference. For instance, the revision direction clearly states that the specific indicators of technical standards should "not deviate significantly from JC-STAR's compliance standards," ensuring coordination and consistency between mandatory security standards and the industry's voluntary certification system. The launch of this system also represents a key measure for Japan to align with international trends in the field of IoT security, such as the United States' Cyber Trust Mark and Singapore's Cybersecurity Labelling Scheme.

2.4GHz SRD technical requirements

Key power and time limits

Test method description:

• Method A: Measure the average power (thermal sensor or RMS  power sensor) at frequency hopping, divided by  the widened bandwidth corresponding to 90% of the total power;

• Method B : Fixed transmit frequency, directly measure the average power.

5.2GHz band wireless LAN

Demand-driven: The demand for high-definition video transmission from drones and other devices has increased, requiring the deployment of 5 GHz wireless LAN in the airspace.In April 2025, the technical standards were revised to allow over-the-air use in the 5.2 GHz band.

Band restrictions：5.3 GHz and 5.6 GHz are still prohibited from using the air due to the risk of radar interference, and only 5.2 GHz (5150~5250 MHz, 200 MHz bandwidth) is open.

Technical Parameters：

RedCap/eRedCap

Demand growth：IoT devices are expected to grow 3.9 times in the 2020s, with broadband IoT accounting for 62%, requiring low-power, low-speed 5G technology.

Standardization：RedCap (supports 150 Mbps) and eRedCap (optimized to 10 Mbps) are standardized by 3GPP, with technical requirements implemented in April 2025.

Comparison of key parameters：

Inmarsat IoT System 

System architecture

Satellite and frequency band：Compatible with 3GPP satellite NB-IoT standard, using Inmarsat satellites, 1626.5-1660.5 MHz uplink and 1525-1559 MHz downlink.

Technical parameters