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i-mode tutorial

- a summary, overview or tutorial about i-mode used for cell phone emails and surfing

i-mode (imode) is cellular technology that has had an astounding success in Japan. Now the company that launched the system in February 1999, NTT DoCoMo, is launching other i-mode cell phone systems in other countries around the world.

i-mode is cellular technology providing an information service, and this give rise to its name. It is provided as a premium add-on service to the basic cellular phone system and provides many facilities including e-mail, internet surfing, and picture mailing. Requiring special i-mode terminals to be purchased by the user, this cellular technology operates as a packet based network overlaid on the basic cellular system.


One of the most popular aspects of the i-mode service is i-mail that enables users to send e-mail messages to others on the same service, or to anyone with an e-mail account.

There are limits to the number of characters that can be sent and received using this cellular technology, but these are much greater than the limits that apply to the SMS service that has become so popular on GSM. For i-mode users can send messages up to 500 characters in length and can receive up to 4000 characters.

On opening an i-mode account, users are given an e-mail address that consists of a random mix of characters. This can be changed once the account has been set up to personalise it for the user, and to make it more memorable.

Internet access using i-mode

The other major element of i-mode is its ability to surf the internet and access internet sites. Specially developed websites using a cut down version of HTML known as cHTML is used to enable sites to be downloaded more quickly whilst providing content that can be satisfactorily viewed on the phones. The i-mode menu on the phone enables the user to select one of four zones: namely Lifestyle (for sports, weather local events etc); Transaction (for facilities including banking, shopping, credit card information and the like); Database (for services including traffic updates, TV and radio schedules as well as cinema information); and Entertainment (where games and music downloads are available along with screen savers, ring tones and hobby information).

One of the major incentives to the development of the special i-mode sites is that the operators have been investing in the content developers to develop official i-mode sites. Rather than splitting the revenues 50/50 as in the case of other similar systems, a revenue share of 90/10 in favour of the content developer has been adopted. This has stimulated a healthy growth and there are many thousands of official i-mode sites, with countless thousands more unofficial ones that are i-mode compatible. This means that the user has a great degree of choice and the usage has risen. In this way the operator has been able to see considerably increased revenues.

On top of these services there is i-shot for taking and sending pictures as well as i-appli for running applications such as downloaded games, and i-area for location based services.

The i-mode system

The i-mode system was originally run on the PDC system that is found in Japan, however it can also be applied to other cellular systems as well.

Based on a packet transmission to the mobile phones, i-mode uses a protocol known as PDC-P (Personal Digital Cellular Packet) for the interchange of data packets. The service is based on a 3 channel TDMA model to provide a common access system that can be shared by multiple users on a random access basis. Using multi-slot transmissions across the three channels data speeds of up to 28.8 kbps can be achieved.

CDMA2000 1X is widespread in Japan, and i-mode system is also used with this system. As data speeds are very much higher for 1X, this enables faster and easier access of the data. Services are also available on the faster data only CDMA2000 1xEV-DO system that enables data transfer at rates up to 2.4 Mbps.


While i-mode is not a mainstream cellular technology in the same way as GSM, or UMTS for example, it managed to gain a good foothold in a number of areas. While it may have been originally seen as a rising sun in the East, it appeared in many other countries to compete with other technologies and cellular systems.

By Ian Poole

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