Mobile Tidings

Another WAP Push over SMS encoding

I still needed to show how you can send an Service Indication (SI) document like:

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< ?xml version="1.0"?>
< !DOCTYPE si PUBLIC "-//WAPFORUM//DTD SI 1.0//EN"
                    "www.wapforum.org/DTD/si.dtd">
<si>
   <indication href="http://mobiletidings.com/"
     created="2009-02-26T16:25:00Z"
     si-expires="2009-03-04T16:25:00Z">Check out Mobile Tidings!</indication>
</si>

This document, a Service Indication, tells the WAP client to store the following:

• A link to http://mobiletidings.com/
• With text “Check out Mobile Tidings!“
• This typically shows up in a “WAP Push Inbox” or sometimes in the “SMS Inbox”
• The link will show when it was created
• It should automatically be removed after the expiry time mentioned

Well here is the AT command to send this particular SI document:

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WAP Push SMS encoding

As I started to explain in the last post, a WAP push consists of an XML document sent to the device over SMS. This is true but somewhat simplified.
The truth is that we send:

• an WBXML encoded XML
• over WSP (Wireless Session Protocol)
• over WDP (Wireless Datagram Protocol)
• over SMS

This is called an unconfirmed push.
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WAP Push over SMS

As you may understand, the data you can send via SMS is limited. It is limited because:

• A single message can only hold 160 GSM-7 encoded characters
• Even though messages can be combined in to bigger ones, the total size is still limited in several ways:
  • A message can have at most 256 parts
  • The receiving device as a (much lower) limit on how many parts it can reassemble into a bigger message
• And if the technical limits aren’t prohibitive, the cost might be

So how do you send more and richer information to a device? There are 2 possibilities:

• WAP push
• MMS

Today I’ll focus on WAP push.

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