Concatenated SMS: UDH decoding

Concatenated SMS: UDH decoding SearchSearch

SMS & MMS Technical Forum » NowSMS Support - SMS Issues (Product Support Only) » Archive through July 14, 2004 » Concatenated SMS: UDH decoding « Previous || Next »
Author Message
Frank Beck
Unregistered guest
Posted on Tuesday, June 29, 2004 - 06:03 am:   

Hello,

got a problem decoding UDH of an concatenated SMS.
This SMS consists of two parts.

This is a sample of second part:

06, User-Data-Header-Length
08,04,00,0E,02,02, UDH bytes
E8,32,28,EC,26,97,E5 text (7-bit default alphabet)

Now I'm wondering how to decode UDH. GSM 0340 says:

Octet 1 Concatenated short message reference number

Octet 2 Maximum number of short messages in the concatenated short message.

Octet 3 Sequence number of the current short message.


So, I would decode it like this:

06, User-Data-Header-Length
08, Information Element Identifier "A"
04, Length of Information Element "A"
00, Octet 1 Concatenated short message reference number
0E, Octet 2 Maximum number of short messages in the concatenated short message
02, Octet 3 Sequence number of the current short message
02, not specified?


I guess the 00 in UDH can be ignored. But where is it specified?
Normally all UDHL had value "05". This time it's 06.
Frank Beck
Unregistered guest
Posted on Tuesday, June 29, 2004 - 06:37 am:   

Forget it.
Now I know how it works:

08, Information Element Identifier "A"

means "Concatenated short message, 16-bit reference number", like described in GSM 0340.

So UDH must be decoded like this:

06, User-Data-Header-Length
08, Information Element Identifier "A" (means 16-bit reference number!)
04, Length of Information Element "A"
000E, Octet 1 (?) Concatenated short message reference number
02, Octet 2 Maximum number of short messages in the concatenated short message
02, Octet 3 Sequence number of the current short message

So in this case "Octet 1" consists of 2 octets. GSM specs can be confusing sometimes.

Login Login / Register Logout Logout Search Last 30 Days Topics Topics