Concatenated SMS: UDH decoding | Search |
NowSMS Support Forums ⬆ NowSMS Support - SMS Issues ⬆ Archive through July 14, 2004 ⬆ |
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Author | Message | |||
Frank Beck Unregistered guest |
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 |
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. |