So, the first thing you need to know is if your cellphone is compatible in Japan.
First, there’s no 2G GSM cellphone company in Japan. If your phone is a simple talk-only or talk-and-text cheap feature phone, it may not work in Japan even if you’re going to use it on the international roaming plan from your own non-Japanese carrier. You need a 3G compatible phone in Japan.
There’re 3 major cellphone companies in Japan; NTT Docomo, Softbank, and KDDI au. If you’re from the United States of America visiting Japan and your phone is from AT&T or T-Mobile US, your phone will probably work on NTT Docomo (W-CDMA/UMTS 2100MHz or 850/800MHz) or Softbank (W-CDMA/UMTS 2100MHz) signals while roaming there, provided that your phone is compatible with 3G 2100MHz frequency. If you’re from the USA and your phone is from Verizon or Sprint, your phone will work on NTT Docomo (W-CDMA/UMTS 2100MHz or 850/800MHz) or Softbank (W-CDMA/UMTS 2100MHz) or KDDI au (CDMA2000 800MHz only) signals in Japan. If you’re from any other countries and your phone is a 3G W-CDMA/UMTS compatible phone, it will work with NTT Docomo or Softbank signals.
Here’s the list of cellphone frequencies used by 3 cellphone companies and their subsidiaries/group companies in Japan.
| Carrier Name | 2G GSM | 3G W-CDMA/UMTS | 4G LTE |
| NTT Docomo | None used | Major Cities:2100MHz (Band 1) Rural Area:800MHz (Band 19 or 6) Limited Area:1800MHz (Band 9) |
2100MHz Band 1 1800MHz(1.7GHz) Band 3 800MHz Band 19 1500MHz Band 21 |
| Softbank | None used | 2100MHz (Band 1) 900MHz (Band 8) 1500MHz (Band 11) |
2100MHz Band 1 1800MHz (1.7GHz) Band 3(*) 900MHz Band 8 TD-LTE 2.5GHz Band 41(*) |
| E-Access (e-mobile) (Softbank) |
None used | 1700MHz (Band 9) | 1800MHz (1.7GHz) Band 3 |
| WCP (Softbank) |
None used | None used | TD-LTE 2.5GHz Band 41 |
| Willcom (Softbank) |
None used | 1900MHz PHS | None used |
| KDDI au | None used | CDMA2000 800MHz CDMA2000 2100MHz |
2100MHz Band 1 1500MHz Band 11 800MHz Band 18 TD-LTE 2.5GHz Band 41(**) |
| UQ Communications (KDDI au) |
None used | None used | WiMAX TD-LTE 2.5GHz Band 41 (WiMAX2+) |
(*) E-Access, WCP, Willcom are the subsidiaries of Softbank. They may roam frequencies each other.
(**) UQ Communications Inc. is a KDDI group company. KDDI may offer UQ’s data service to KDDI customers.
In addition, there’re several MVNOs which use NTT Docomo’s signal, such as b-mobile, IIJ, etc. And, there’s one MVNO that uses KDDI au’s signal; K-Opticom’s “mineo” brand. I’ll talk about the MVNOs in Japan on a separate article later.