This article is written by a Japanese local.
When foreign employees relocate to Japan, there is a near 100% probability that they will bring the “smartphone they use in their home country” and attempt to use it by simply inserting a Japanese SIM card.
However, the assumption that “inserting a SIM card guarantees connectivity anywhere in the world” is incorrect. To establish communication, the “frequency bands (Band)” provided by Japanese telecom companies and the “receiving antenna” of the imported device must physically match. Ignoring this leads to serious troubles such as “connecting outdoors but losing signal inside buildings” or “not picking up any signal at all.”
This article explains the objective technical and legal requirements that HR managers should have employees confirm before departure to ensure reliable communication with their imported devices.
1. The Absolute Condition of “SIM-Free (SIM Unlocked)”
[Summary] If the device is locked to a telecom carrier in the home country, a Japanese SIM will not function. Completing the unlock procedure before departure is mandatory.
Before even discussing frequencies, the imported device must be “SIM-Free” (in a state to accept SIM cards from any telecom company). Devices purchased from overseas telecom companies (e.g., Verizon or AT&T in the US) are frequently “SIM-locked” so they can only use that specific company’s SIM card.
This SIM lock cannot be unlocked at mobile shops in Japan. If the lock is discovered after arriving in Japan, an extremely difficult procedure arises involving negotiating with the home country’s telecom company via international phone calls. Ensure you strictly enforce the rule to “unlock the SIM in the home country before departure.”
2. Japan’s “Frequency Bands (Band)” and the Platinum Band Wall
[Summary] If the frequency bands (Band) used by Japanese carriers and the device’s supported signals do not match, the phone will go “Out of Service.”
Radio waves around the world are regulated, and the usable frequency bands (Band) differ by country and carrier. When using the networks of Japan’s major carriers (Docomo, au, SoftBank), you must check the device’s specification sheet to ensure it supports at least the following Bands:
- Essential Basic Band (Band 1): A fundamental frequency (2.1GHz) widely disseminated across Japan. Without this, proper communication cannot be established.
- Platinum Bands (Band 8 / 18 / 19 / 28): Crucial frequency bands that curve around “obstacles” to reach deep inside buildings, underground, and mountainous areas. Depending on the network, support for “Band 19” (Docomo), “Band 18/26” (au), or “Band 8” (SoftBank) is indispensable.
In the case of inexpensive Android devices meant for overseas markets, they frequently support the basic “Band 1” but lack support for Japan’s Platinum Bands. In this scenario, the user falls into an extremely unstable state where “the phone connects while walking outside but goes out of service the moment they enter an office or apartment.”
3. The Legal Hurdle of the “Giteki Mark (Technical Conformity)”
[Summary] Using a device without the Technical Conformity Certification (Giteki) under Japan’s Radio Law is generally considered an illegal state.
When using devices that emit Wi-Fi, Bluetooth, or mobile radio waves within Japan, it is legally required that they bear the “Giteki Mark,” which proves they have cleared the standards of Japan’s Radio Law.
Many smartphones purchased overseas do not possess this Giteki mark. While there is an exceptional mitigation measure that “permits use limited to 90 days after entry,” continuing to use a device without a Giteki mark for long-term expatriates is not recommended from a compliance perspective.
4. Practical Q&A (Troubleshooting for HR Managers)
[Summary] Answers practical questions regarding local procurement if incompatible, and the difference in adaptability between iPhones and Androids.
Q. It is difficult to check compatibility for every model. Are iPhones okay?
A. Apple’s “iPhone” series (iPhone 8 and newer) are manufactured covering a globally common set of Bands, so they support Japan’s Platinum Bands and standardly feature the Giteki mark. Conversely, “Android devices” by foreign manufacturers (overseas sales models of Xiaomi, OPPO, Samsung, etc.) often have antenna components scaled back (localized) to match the selling country, resulting in many cases where they cannot properly pick up signals in Japan.
Q. What should we do if the imported smartphone is incompatible with Japan’s Bands?
A. Physical hardware limitations that prevent signal connection cannot be solved by changing settings. The most reliable approach is to not force its use, but instead instruct them to purchase a “SIM-free smartphone compatible with Japanese standards (inexpensive models around tens of thousands of yen)” at a domestic electronics retailer, or to apply for a handset bundle plan when contracting with an MVNO (Low-Cost SIM).
Conclusion: Prevent Infrastructure Mismatches with “Prior Spec Confirmation”
Even if the mobile phone contract itself is completed, securing a means of communication will fail if the hardware of the imported device is incompatible with Japan’s radio network (Bands). HR managers must provide a company guideline one month prior to relocation regarding “SIM unlocking” and “confirming the device’s supported Bands (especially Platinum Bands),” thoroughly instructing them to budget for purchasing a terminal in Japan if incompatible.