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In Japan,Cellphone compamy's Big 3 is NTT docomo(45%),au/KDDI(29%),Softbank(25%). then next is Y!mobile(Softbank group).

 

Each company's features

 

1.NTT docomo

NTT was public company "Nippon Telegraph  & Telephone company". established in 1952. Telegraph's history and Telephone history and cellphone history and fiber optic history were made by NTT. NTTdocomo's cellphone system has been developed by themselves. That's why monthly fee and cellphone body cost are comparatively higher than other cellphone companies.

 

NTT docomo's cellphone frequency

＠LTE... 700Mhz Band28 /800Mhz Band19 /1.5Ghz Band21 /1.7Ghz Band7 /2.0Ghz Band1

@3G... 800Mhz and 2.0Ghz 

 

NTTdocomo has low frequency. Low frequency can reach so far and can jump over the obstacles like tall buildings and tower. NTTdocomo's digital 3G service is WideBand CDMA. Most popular 3G service all over the world. If you have this company's flip cellphone,you can easily unlock it by cheap cost. But some iphone can't be unlocked. Consult me.

 

Anyway NTTdocomo's benefit is Shop girls are so beautiful. That's why monthly fee is high. Remember it.

 

 

 2. au/KDDI

Company name is KDDI. Cellphone brand name is au. au is pronaunced EIYU. It means "A"ccess tu "U". KDDI was established in 1985. First company name was DDI. DDI means the second NTT. Later DDI had merged KDD(Public international telephone line company), then in 2000,DDI changed their name to KDDI. Most of KDDI's cellphone system has been used American technologies cos it is low cost.

 

This company's digital 3G service is CDMA2000(CDMA One). It's not popular cellphone system. KDDI's cellphone and Verizon's cellphone are almost compatible. If you have Verizon's SIM free cellphone, you can use KDDI(au) SIM card for telephone and 3G data. But now au don't sell just SIM card.  and if you bought au cellphone,then when you go back to your country. Do you wanna unlock? But we don't know if you could use it in your country. Consult me.   

 

 

3. Softbank

This company's first name was Tokyo Digital Phone established in 1991. The owner was JR(Japan Railway). JR made Nippon Telecom(Private long distance telephone calling company) then Nippon Telecom made Tokyo Digital Phone. But later British  company Vodafone bought Tokyo Digital Phone but didn't succeed. then in 2004,Softbank bought Vodafone Japan branch. Before,this company's signal available area were so narrow. 

 

Softbank cellphone's 3G system and most of devices are compatible to NTTdocomo. They use WideBand CDMA too. and Connecter shape is as same as NTTdocomo's cellphones. NTTdocomo's flip phone's battery charger can be used to Softbank flip phones. But not all. be careful. 

 

Softbank don't have lower frequencys. That's why this company's cellphones are often not available in the building,between buildings and country side and mountain side and sea side. But gradually Softbank is installing more base stations. 

 

4.Y! mobile

Y!mobile is one of  group company of Softbank.

This company's PHS cellphone service is so reasonable. But they wanna stop PHS service as soon as possible. That's why I canceled PHS service this year. Anyway be careful. Softbank group's contract paperworks have many traps. Until you cancel,you don't know how much cancellation fee you need to pay. XD  

 

 

4.NTT docomo's compatible SIM card companies.

There are almost 20 companies. I can't check all. They borrow NTT docomo's cellphone network system and facilities. That's why NTTdocomo's name is printed on their SIM card. But NTTdocomo don't recognize their customer's information. (CAUTION) cellphone's voice quality is as same as NTTdocomo's. But Internet speed is big difference. Some are good speed but some are slow speed. Before buying it,consult me. Anyway These company's SIM cards are so cheap and reasonable. If you don't need much functions and services,I recommend this SIM cards. You can save your money a lot.

 

 

If you wanna use cellphone in the US military's base.

NTTdocomo is best signal strength but total cost isn't so cheap.But you can make it SIM free cellphone.

au is better signal strength than Softbank but you can't make it SIM free cellphone.(Maybe you can use Verizon's SIM card in USA)

Softbank is lower cost but you can't make it SIM free cellphone.(It depends on when you bought Softbank cellphone).

 

It's so complicated.... Often even me is confused. Anyway consult me.