Home Introduction Wireless Application Protocol Comparison of WAP and iMode Conclusion References
Delivering the World Wide Web on Wireless Menu


iMode History

An example of an iMode mobile phone iMode is a service that was introduced in Japan in early 1999 by NTT DoCoMo, a subsidiary of Japan's former national telephone monopoly, NTT (and one of the world's most highly-valued companies). It has rapidly become one of the most successful subscription services on the planet, with young Japanese (and in particular women in their late 20s) signing up at a rate of 50,000 per day to use their phones for browsing online information and sending and receiving e-mails. For many of these users iMode is their only experience of Internet access, as Internet penetration is much lower in Japan (13.4 per cent in 1998) than in other developed countries (e.g. 37 per cent in the US in 1998), and Internet access is charged for based on time spent online (at exorbitant local call rates). Also, Japan had a very high rate of mobile penetration before iMode was introduced, and many Japanese are fascinated by gadgets, so the novelty of iMode was a bonus. As of late 2000, iMode had an estimated 14 million users.

Customers use iMode for a wide variety of purposes but among them are included: receiving news and stock prices, sending and receiving e-mail, shopping online and online banking. iMode technology is also used in car navigation systems to provide traffic news, to give localised weather forecasts and parking updates amongst others things.

iMode Features

Because NTT DoCoMo controls every aspect of the iMode infrastructure, it has been able to implement advanced features and services for the network. Among the important points concerning iMode are the following:

  • Proprietary Protocol
    Although iMode is not just a protocol, but a complete infrastructure, it is important to remember that NTT DoCoMo can decide what conditions it must be used under and whether other network operators or content providers should pay to use it.
  • Control of Content
    Because all iMode subscribers must currently use one network operator, NTT DoCoMo, that company has configured its phones to automatically only list content and services that it provides on the display menu. So it has been able to establish itself, through the creation of 500 official sites, as the primary source of information for people on the move. The 20,000 or so unofficial iMode-compatible sites that are available can only be accessed by typing in a URL (not an easy task using a phone keypad). This has led to a situation where only 15 per cent of traffic comes from outside NTT DoCoMo's portal site.
  • Micro-Billing
    Value-added services and customised content can easily be charged for by content providers as they can simply be added to a user's phone bill.
  • Uses Packet-Switched Network
    While NTT DoCoMo's existing mobile network was based on a circuit-switched network, the iMode overlay uses the PDC-P packet-switched network. iMode will work on either type of network, but because it is on the packet-switched type in Japan, users have an "always-on" connection, meaning that they are perpetually connected to the Internet as long as they are in an area of suitable coverage. The underlying packet-switched network also allows users to be charged based on the volume of data transferred.
  • Phone Displays
    The screens on iMode phones are generally grey-scale, not monochrome, allowing users to view newspaper-quality images. Some advanced models have 256-colour displays and can display simple animations. All phones can view images in GIF format, which is already a de facto standard on the WWW (though a colour GIF may have to be rendered in grey-scale due to the limitations of individual phone models).
    The display capabilities of iMode phones also allow the provision of entertainment and games (as proven by the recent link-up between NTT DoCoMo and Sega). One of NTT DoCoMo's most profitable services is the option to download a daily cartoon: its 10 million subscribers earn the company $120 million annually.
  • E-Mail
    Because NTT DoCoMo is the exclusive provider of iMode, it was able to assign all users an e-mail address automatically (based on their DoCoMo mobile phone number). This allows users to participate in one of the Internet's most popular activities (sending and receiving messages) without having to worry about finding a service provider or configuring software. Because of limited bandwidth and hardware considerations, e-mails are limited to 500 bytes (250 Japanese characters or 500 Latin characters) and attachments are not allowed.

Compact Hyper Text Markup Language (cHTML)

In creating a markup language to display material on its iMode phones, NTT DoCoMo seems to have come to the conclusion that the best course of action was to ensure that its iMode service was saturated with content and applications from the initial launch. They were keen to ensure that content providers, especially their own in-house writers and developers, would have little trouble producing information for display on users' phones. With this in mind they made several important decisions with regard to cHTML:

  • Subset of HTML
    iMode's markup language, compact HTML, is defined as a subset of the HTML 2.0, HTML 3.2 and HTML 4.0 specifications. This means that cHTML inherits the flexibility and portability of the standard that is used on the Web. Since cHTML is almost completely based on the HTML recommendations, it can avail of the extensive range of HTML-based content resources, various software tools, and public materials that are in existence today. However because cHTML has to be displayed on phones with minimal amounts of memory and low-power CPUs, certain HTML features were excluded from its specification. Other features were excluded due the impossibility of navigating them with the four rudimentary navigation buttons available on an iMode phone (Cursor Forward, Cursor Backward, Select and Stop). The main HTML features which are excluded from cHTML are as follows:
    • JPEG and PNG images
    • Tables
    • Image maps
    • Font family or font style specifications
    • Frames
    • Style sheets
  • Proprietary Tags
    As well as HTML tags, some extended tags, which only an iMode browser will make use of, have been introduced. These allow the author of a cHTML page to indicate to a search engine that the page is intended for viewing on an iMode phone, or to create a link that, when activated, dials a telephone number. NTT DoCoMo also introduced many extra special characters, such as "emoticons" (pictures to represent joy, sadness etc.) and some Japan-specific symbols (such as a symbol for the Bullet Train).

iMode Problems

Most of the potential weaknesses with iMode are to do its proprietary nature. If iMode is to expand outside of Japan these weaknesses must be overcome:

  • Geographically Limited
    At the moment, although cHTML pages are visable anywhere in the world on a WWW browser, only consumers within Japan can use their mobiles to view them. Outside of Japan iMode is virtually unknown except among those with an interest in wireless Internet technology.
  • Geared Towards Japanese
    As iMode was designed only with the Japanese market in mind, it has some quirks that at the moment make it imperfect for deployment in Europe. For instance, text is wrapped at the edge of the screen regardless of word boundaries. In Japanese, this does not matter, as spaces are not needed between words, but in other languages this leads to individual words being split between two lines, which makes text hard to read. This would probably be changed when iMode is deployed in Europe.
  • Protocol Control
    Potential iMode content writers and application developers outside of Japan may resist using a service or protocol that can be changed at any time at the whim of NTT DoCoMo. While NTT DoCoMo retains licensing control of iMode it is unlikely to take any action to jeopardise its position or profits, even if that action would benefit the greater community of iMode users.