Japan is the new year holiday season from the end of December to the early January. This is also the time when people come back to their hometown and stay with relatives and friends. One of my friends also came back from a place which is far from Tokyo by using Shinkansen which is very famous bullet train all over the world. I met him at the Tokyo station and talked a lot about what we did in the 2013 at a beer bar. It is always fun to meet people for a long interval. On that day, we were going to meet around 6 pm at the station, and I sent an email to him to make sure of it around noon, but I did not receive the reply even after a few hours. So I was wondering what's going on him and I finally called him even by considering that he might be in the train, but what I heard was a automatic guidance saying that his cell phone was turned off or he was in a place where signal is not available. He responded back my email just one hour before the time. What is interesting to me was that he turned off his cell phone purposely and turned on it again after he got off the train. According to him, cell phone battery consumes much faster than he usually uses it. It is coincident because I have study the modern communication system recently by myself and just understood how moving mobile phones stay connected with base stations and how it works technically.
We basically call to somebody and send date like email through base stations which manage much traffic on behind. Each cell phone has to be connected to base stations anytime in order to work properly and base stations have to know how many users there are, how far they are and much information which is necessary for optimized communication. As the figure above shows, each base station has own cover area, and mobile users in, for instance, area A are supposed to communicate with the base station in area A. In order to stay connected together, mobile phone and base stations send and receive their information even though users don't use cell phones unless cell phones are turned off. If users don't move much, then their communication environment doesn't change much, so cell phones and base stations does not necessarily communication much. However, if the user moves fast, what happens is that users go through ares of base stations much, and cell phones try to connect to a new base station every time when users cross a boarder from one are to adjacent area. Precisely, connecting to the new base station is relatively much burden on mobile phones because it takes much calculation in order to estimation transmit path information together with the new base station. It means much power consumption. So that's why battery consume faster in a bullet train.
This is my understanding.
The picture is from
http://www.odec.ca/projects/2007/hopp7m2/Cellular_Phones.html
