Major kudos if they are as wide spread as they sound. I was able to talk with family in Japan using Skype even though their cells were out... so this will definitely help people.
Yesterday's news said the mobile phone didn't work, whereas wireline network was still functioning. I strongly suspect this is not due to an outage in the network, but rather intentional.
Some years ago I worked on a project for a Japanese mobile operator to implement a system that prevents "normal" mobile phones from making calls to avoid overloading the network. When activated, only emergency services (fire fighters, police, medical, ...) are allowed to call. At regular intervals, a batch of the "civilian" phones are allowed too for a while, then a different batch, etc, so everyone gets its chance to call if they wait long enough.
The system was a government requirement for events such as yesterday's quake, but I can't confirm all phone disturbances reported were/are due to it.
Technically, it relies on a bitpattern called "accessClasssNBarred".
This reminds me that another way for fellow Japanese to help their compatriots would be to remove the passwords on their wireless networks and rename the SSID to "Free Wi-Fi for those who need it".
They are pretty big in japan. I've noticed a big increase in the past year or so; a lot of places that previously offered their own free service now have a for-pay Fon access point. (in the Kobe area, anyway)
In Portugal, Fon partnered with Zon (an ISP operation of the major cable TV provider). A couple of years ago, the cable-modem/wireless-router combo boxes, mostly Netgear hardware, had an option to turn on the Fon service, which was off by default.
That must have been not working very well. So, around August 2010, they updated the firmware in the routers, including those already deployed, to turn on the Fon option by default. Plenty of access points now available ...
(Details: although it uses the same radio and bandwidth, the public Fon access point uses a different IP; it requires a password which anyone who provides Fon access in his wireless router can have by registering with fon.com)
