WAP Service Developer's Guide for Nokia Series 40
Version 1.0
Copyright © 2002. Nokia Corporation. All rights reserved.
7
2.3.3
Usability tips for WAP over GPRS service development
Round-trips in a network always cause a minimum of a two 2-second delay to the response
time. Therefore, the number of round-trips should be minimised. For example, bitmaps cause
additional round-trips. The response time can also be minimised by keeping the size of a
WAP deck as compact as possible; this is especially important for pages that require an
instant response. The response time of the first deck has a strong impact to on the user
experience. Therefore, it is worthwhile to maximise Infrastructure optimisation.
Minimise latency between the WAP gateway and content server. Remember that each query
traverses this link twice, once as a request and once as a response.
Place the WAP gateway close to the GPRS gateway. (The GPRS gateway is technically called
a “Gateway GPRS Support Node”, or GGSN.) “Close” in this instance refers to both latency
and probability of packet loss. Lost messages cause additional delay due to HTTP-
retransmission.
2.4
Site organization
2.4.1
Avoid “doormat” pages
The user accesses your WAP site over a GSM data call, and pays per second. It is not
recommended to start your site using a “doormat” page, which serves no purpose other than
perhaps to greet the visitor and to display a logo. It is better if the user can go to your
service directly. If there is a need to use a timer, it should not be longer than ~1.5 seconds.
Otherwise, add a link incorporating the text “continue” to give the user the possibility to exit
the card.
2.4.2
Automatically detect the browser
If you are using a modern Web site hosting environment, it is possible to detect the browser
as well as the language mode and to supply correct content transparently without user
interaction.
Nokia WAP phones send a user agent field in the WSP header to the WAP Gateway when
they fetch content from the origin server. You can use this user agent field to define the
browser type and then build the logic on the origin server to serve suitable content. From the
WAP Gateway, it is then delivered inside the HTTP header.
The user agents for different Nokia phones can be found in the WAP Characteristics table on
www.forum.nokia.com
2.4.3
Optimize for size
The size of the content is critical. If you have large decks (for example, lists and large tables),
consider splitting them into multiple parts for faster downloading.
As for the total downloading time, some studies place an upper limit for an acceptable delay
on a PC-based browser at 10 to 15 seconds, including all images. It is highly recommended
to have a response time (excluding connection time) in a mobile environment that is less
than 10 seconds.
