System of Packet Charges

Packet communications used for browsing sites in i-mode and mail is a communications method that divides transmission data into smaller segments called packets. Normal voice calls use the technology of circuit-switching communication where the time spent talking with the other person occupies one communication line. When all the communications lines that can be used when making calls are full, the user will have to wait until one of the communication lines becomes available. In the case of packet communications, by breaking the data up into smaller units, numerous people can share one line so the communications line can be used effectively.

The size of data handled on computers is represented by units called bits and bytes. A bit is the smallest unit of data, and data represented by 8 bits is called 1 byte. In terms of characters, a half-size character is equivalent to 1 byte, and a full-size character to 2 bytes. The packet unit in i-mode packet communications is equivalent to 128 bytes. This means that 64 full-size Japanese characters can be transmitted in 1 packet. However, a packet contains a header that includes information such as the destination address so the number of characters that can actually be transmitted in 1 packet is less than 64 characters.
When you browse sites in i-mode, the data required for display is sent from the sites in addition to the characters and images. The transmitted data contains not only the displayed characters but also the information required to specify the position of characters and colors on the screen, and other data required for packet communications.

Packet communications charges are billed according to the volume of data (number of packets) that is sent and received. Circuit-switching communications where one person occupies one communication line are charged only by the length of the time spent using the communication line. On the other hand, because numerous people use a common communication line, packet communications charges are calculated by the actual volume of data that is transmitted and not the call time.
It is easier to understand by comparing it to a letter sent in the post. The charge is determined by the weight of the letter and not the distance to the destination or the time taken to deliver. Likewise packet charges are billed according to the volume of data, so users can search for and view the information they want without worrying about the time spent transmitting the data or the distance involved.

Packet communications charges are calculated from the total number of packets that have been used in one month and not the number of packets per transmission.

If you register frequently used sites as bookmarks, you can directly access the sites you want to view. In such cases, packet communications charges for navigating to sites will not apply, so you can save on charges compared with when you access sites that have not been registered.

You can check your usage for the current month and billing information for the past three months by mobile phone or PC at the Billing Details Confirmation website. Application in advance is not required.

Billing Details Confirmation

Charge Notice Service is a convenient service for preventing overuse of voice and other communications. It notifies you by e-mail when the total amount of your monthly dialing charges, packet communications charges, i-mode information charges, etc. exceeds the amount you set in advance (¥5,000 or more in ¥1,000 increments). You can select up to two notification destinations, such as the i-mode mail and Internet mail addresses you have specified.

Charge Notice Service

Two-tiered packet flat-rate service for unlimited i-mode and mail use

Pake-hodai double

Starting from an affordable ¥390 per month, get worry-free use with a maximum charge of ¥4,410 even for heavy i-mode browsing and i-mode mail use.

i-mode Access History Search Service

You can search and view a history of your i-mode usage on a PC via the Internet.