Notes
Outline
Considerations on the Mobile Internet Architecture for High-Speed Wireless Networks
INET 2001 Poster Session
June 5th – 8th , 2001
NTT DoCoMo
Authors Information
Norihiro Ishikawa
(NTT DoCoMo Inc., Multimedia Labs.)
Email: ishikawa@mml.yrp.nttdocomo.co.jp
Hideharu Suzuki
(NTT DoCoMo Inc., Multimedia Labs.)
Email: hideharu@mml.yrp.nttdocomo.co.jp
Hidetoshi Ueno
(NTT DoCoMo Inc., Multimedia Labs.)
Email: uenohi@nttdocomo.co.jp
Background
Internet access from wireless environment (mobile phone, PDA) is being increasing.
WAP Forum has developed WAP1.x protocol that is optimized for wireless networks that have the characteristics such as high latency and/or high error rate.
Functions and the performance of the WAP protocol have not fully evaluated.
We have measured the performance of the WAP protocol and compared it with that of the Internet protocol.
What is WAP?
WAP is developed by the WAP Forum (established in 1997).
WAP is a protocol that is optimized for wireless environment (mobile phone, PDA etc.)
Consists of WAP client, WAP getaway and Origin server.
Optimized for wireless network characteristics and provides special functions.
Telephony application, push functionality, suspend & resume
WML(Wireless Markup Language) and binary encoding
Many kinds of bearer support (GSM, CDMA, PDC, SMS…).
WAP Architecture
WAP Protocol stack overview
WAP1.1 test-bed system overview
Evaluation on WAP
We evaluated the following items on the WAP test-bed system.
Functionality evaluation
WAP Push
WAP push is one of the unique functions in WAP. Investigating feasibility of WAP push is very important.
We developed an e-mail application prototype by using the WAP push function.
Performance evaluation
Response time
Since response time is one of the key factor of serviceability, we compared the response time of WAP1.1 and HTTP/TCP.
WML binary encoding compression rate and processing time
WML binary encoding is one of the unique functions in WAP.
Push functionality evaluation(1/2)
What is WAP push?
The WAP Push framework introduces a means to transmit information to a WAP client.
WSP defines push methods (confirmed and unconfirmed push) in addition to the methods defined by HTTP.
Push functionality evaluation (2/2)
We developed an e-mail application prototype by using the WAP push function.
Protocol conversion (SMTP to WSP) is executed at the WAP gateway, and e-mail messages are pushed to the client immediately.
Considerations on Push functionality
An immediate push of a message (e.g. e-mail, instant message) is desirable, from the mobile user’s point of view.
We concluded that the WAP push functionality fulfils the above requirement.
WAP push is very feasible and usable in the wireless environment.
WAP performance evaluation 1 (Response time)
Evaluated the response time (from request method to reply method) of WAP1.1 and the Internet protocol (HTTP/TCP) over W-CDMA environment.
W-CDMA emulator emulates W-CDMA environment, which can set up bearer speed, bearer error rate, latency and so on.
Bearer speed
Uplink: 64kbps (fixed)
Downlink: 384kpbs, 64kbps
Bearer error rate:10%
Contents size
500, 10K, 100Kbytes
Protocol parameters
WTP maximum group size: 9600bytes
TCP receive buffer size: 9600bytes
Response time comparison
Considerations on response time
WAP1.x would take an advantage if content size were small, HTTP/TCP would take an advantage if content size were large.
500byte(64kbps): WTP1.x is better than HTTP/TCP.
100Kbyte(64kbps): HTTP/TCP is better than WAP1.x.
Reason
Because TCP slow start algorithm prevents making full use of network resources in the slow start phase, WTP is better than TCP in case of small contents.
WTP responder can send the number of packets based on the window size, but the WTP responder has to wait until the subsequent acknowledgement is received. That waiting time results in the increase of total response time.
TCP performance is better when transmitting large contents because dynamic flow control mechanism works well provided that the large size of buffer is prepared in the client.
WTP and TCP communication sequence comparison
WAP performance evaluation 2 (WML binary encoding)
WAP defines binary encoding of WML.
A WML content is encoded into binary format at the WAP gateway.
We evaluated WML binary encoding compression rate as well as processing time compared with gzip.
Content size: 500, 1000, 1400, 20K, 100K, 360K
Binary encoding example
<wml>
 <card id="abc" ordered="true">
  <p>
   <do type="accept">
    <go href="http://xyz.org/s"/>
   </do>
   X: $(X)<br/>
   Y: $(&#x59;)<br/>
   Enter name: <input type="text" name="N"/>
  </p>
 </card>
</wml>
WML binary encoding comparison
Consideration on WML binary encoding
If content size were small, WML binary encoding would be effective. On the other hand, gzip encoding would be effective if content size were large.
WML encoding processing overhead would increase considerably if content size were large. (In case of 360K, then 1730ms.)
Discussion
WAP1.x would take an advantage if content size were small, HTTP/TCP would take an advantage if content size were large.
Since 3G network handles larger contents than 1G/2G, HTTP/TCP is more suitable than WAP1.x in the 3G multimedia environment.
We propose the mobile Internet architecture that is suitable for high-speed wireless networks such as
W-CDMA.
Consideration on proposed architecture
Seamless Internet access.
Provide End-to-End security by using TLS tunneling.
HTTP/TCP would take an advantage if content size were large.
Markup Language
Experience with the deployment of i-mode.
Since i-mode adopts subset of HTML and contents developers are familiar with it, there are many i-mode contents in the Internet.
XHTML is expected to be the next generation markup language. And XHTML Basic is expected to be a core language for clients such as mobile phones that do not fully support of XHTML features.
Push functionality
WAP push is very feasible and usable in the wireless environment.
Provide push functionality over TCP by using HTTP POST (implementing HTTP compact server on the phone, and HTTP client on the WAP Gateway).
Proposed Mobile Internet Architecture for 3G network
Conclusion
We developed WAP1.1 test-bed system.
Performance evaluation has shown that WAP1.1 is suitable for application of small content size.
In 3G network, bearer speed is very fast (384kbps-2Mbps) and contents are becoming large, so that Internet standard protocols(HTTP/TCP) is applicable to the wireless environment with some TCP modifications.
We proposed Mobile Internet Architecture for high-speed wireless networks such as 3G.