Architecture of iMode
Matthew Caesar
4/3/02
What is iMode?
Goal: Easily enjoy Internet services on mobile
phone
Overlay on top of DoPa packet network
Subscriber:

New, advanced services on mobile device
Operator:



A way to attract new users and increase revenue
Users charged on per-packet basis (~0.22
cents/128byte)
Payment collection for third-party information
providers
Statistics
iMode a huge success

Today, 80% of world’s wireless Internet users are
in Japan (12.5% in Korea, 5% in Europe, 1% in
USA)
 2% of world’s population is in Japan


Zero to 26M subscribers in 2.5 years, 50K more
per day
1,000 official sites; 30,000 voluntary sites
Early deployment



Packet network launch 1997
iMode launch 1999
-> Lots of time to experiment and learn
Goals
Stick to telephone

Enjoy Internet without bulky, slow PDA or PC
Easy to use


Users unaware of Internet
Adapt browser to mobile device
Leverage Internet technologies

IP, TCP, HTTP, SSL, Java
Media diversification

Allow third parties to provide information
Architecture
Info.
Provider
Info.
Provider
Packet iMode
Network Server
(PDC-P)
Communication
Network
(PDC)
PSTN
Info.
Provider
Internet
PC
Groupware
Server
PC
Packet Network (PDC-P)
iMode Server
M-SCP
M-PGW
M-PGW
M-PGW
PGW
PPM
PPM
BS
BS
BS
BS
MS
MS
MS
MS
I-MAX
I-MAX
I-MAX
Interne
t
IP
IP
BS: Base Station
PPM: Packet Processing Module
PGW: Packet Gateway Module
M-PGW: Mobile Message-Packet
Gateway Module
M-SCP: Mobile Service Control Point
I-MAX: Interface-Mobile Access
Exchanges
iMode Server
M-PGW
SW
I-MAX1
SW
RT
I-MAX1
U-MAX
M-MAX
C-MAX
W-MAX
To PDC-P
To PDC-P
M-PGW
N-MAX
M-PGW
SW
Customer
Center
SW
ISP
1
ISP
2
Leased Line
Leased Line
Leased Line
I-MAX8
Maintenance
Terminal
SW
RT
Itemization
Center
RT
SW
F/W
RT
SW
F/W
RT
SW
F/W
Functions:


IP
RT
B-MAX
D-MAX
RT
SW


To PDC-P
Internet Access
Proxy
Mail Storage
User Management
Information charging
Sales
Analytic
Terminal
Business
Remote
Terminal
Protocols
TLP
Improved efficiency in PDC-P network over TCP (uses fewer packets to save
charges)
Higher data packet ratio
No 3-way handshake, control signals can piggyback data



ALP


Supports both pull (HTTP) and push style communication
Direct HTTP communication between mobile phone and iMode server
UITP (User Information Transfer Protocol) sends subscriber information
from PDC-P network to iMode server
NWMP (Network Management Protocol) performs signaling


Start/end of packet communication
E.g. email delivery, push content notification
HTML
Mail
Telephony
Function
ALP (Application Layer Protocol)
PDC
PDC-P
iMode
Server
ALP (Application Layer Protocol)
TCP
TLP (Transport Layer Protocol)
IP
Security
SSL (adopted March 2001)

End-to-end SSL(e-eSSL) with server-side authentication
 Phones have pre-configured keys

Client-side authentication is future work
 Non-repudiation is not yet possible


Can also do SSL just between IP and iMode server (s-sSSL)
PDC-P network doesn’t have to be trusted
Java


Can run applets from IP
Java Application Manager (JAM) prevents access to handset
Current and Future Services
Digital Music Distribution
Car Navigation System
Email
Internet/web access
E-Commerce
Video-calls
Streaming media
Java Games
Schedule Management
File sharing
BBS
Multi-party Conferencing
Workflow Management
Mobile TV
Interactive TV
Video distribution
Music Distribution
Mobile Banking
Concert Ticket Booking
Club/Event Info
Travel Service
Downloadable Characters
Credit Card Bill Inquiry
Horse Racing Information
Mobile Trading
Location Information
Karaoke
Horoscope
Fortune-telling
CAD
Dictionary search
Complex vector graphics
Restaurant guide
Flash software
Walking/driving/subway directions
News
Animated Mail
Housing information
Vending Machine Interface
Weather forecast
Telephone directory
Airline information
Hotel Reservation
Discount Tour Info
Stock Information
Cooking Recipes
Application Scenario: Railroad
Facility Management System
Japanese railroad companies use PDAs



Display diagrams of wires, tracks, signals, communications
Collect data and workflow management
Consider using iMode phone instead
Disadvantages of PDA:




Too heavy, difficult to operate
Low bandwidth (wired)
No dynamic updates
Expensive
Disadvantates of iMode phone



Small display size
Spotty coverage (tunnels, near buildings)
Low bandwidth (wireless)
M. Kikuchi, Y. Yagi, “Use of iMode Cellular Phones for Facility Management System”
Hardware Demands
Low Power Ics


Most power consumed by power amp
New applications require more power
 SSL, Multimedia, Java
Memory


10x larger memory required
Non-volitile storage required for media downloading services
LCD

More colors, faster response speed => greater power drain
Battery

Currently 30% of unit total weight (large)
H. Yazaki et. al., “Overview of Advanced iMode Mobile Phones”
K. Enoki, “iMode: The Mobile Internet Service of the 21st Century”
Comparison with WAP/WML
WAP
Specification for presenting and
interacting with information on
wireless
Sites based on new WML
39% of world’s wireless
internet users
Usually used over circuit
switched connections
Services business-oriented,
work-oriented
Anyone can produce content,
content menus
iMode
 Wireless internet service (could
be deployed over WAP)
 Sites based on HTML (cHTML)
 60% of world’s wireless
internet users
 Usually used over packet
switched connections
 Services user-oriented, funoriented
 Anyone can produce content,
DoCoMo operates content
menus
Recent News
iMode Launch in USA via ATT wireless


Expected to launch soon
Stripped down service
Currently being deployed in Europe by
E-Plus

Already deployed in Germany
References
Web sites:



The iMode FAQ: http://www.eurotechnology.com/imode/faq-sec.html
http://www.acsac.org/2001/papers/61.pdf
Official iMode Site: http://www.nttdocomo.com/imode/top.html
“Special Issue on iMode Service”, NTT DoCoMo Technical Journal, Oct.
1999.
“Special Article on Advanced iMode Mobile Phones,” NTT DoCoMo
Technical Journal, Jun 2001
“Wired versus Wireless Security: The Internet, WAP and iMode for ECommerce”, ACSAC 2001
“iMode: The Mobile Internet Service of the 21st Century”, ISSCC 2001
“Learning from iMode,” IEE Review, Nov. 2001