explain sms UDH header 08 07 01 03 00 03 08 02 02?

Question

i have read udh details from concatenated-sms

but those example are like

05 00 03 A6 02 01

And

06 08 04 F4 2E 02 01

but i have received sms with this header

08 07 01 03 00 03 08 02 02

i know first octet 08 is header length

2nd octet information elemint identefier is (07) that is udh source indicater ?

can anyone explain what is meaning of udh source indicater and all others octets ?

Answer 1

Usually this UDH including UDH-Source-Indicator is included in a SMS STATUS REPORT. It can also be the case that the sending SMSC injects UDH elements also into the UDH.

Extracted from 3GPP specification 23.040 ( Technical realization of the Short Message Service (SMS) )

The facility is used to separate the UDH of the original message, a UDH created by the SMSC, and a UDH provided by the original receiving entity. The Source Indicator is placed in front of the content inserted by the source. The indicated content (one or more Information-Elements) ends at the next UDH-Source-Indicator, or at the end of the UDH. The Separator is intended to be used especially in Status Reports, but can also be used by the SMSC to add information into Short Message (for example Message waiting). The default content for a UDH in a SMS-DELIVERY is the headers inserted by the sending device, and the default content for a UDH in a SMS-STATUS-REPORT is the headers copied from the SMS-DELIVERY-REPORT.

Decoding the UDH by hand shows that there are infact two Informational Elements included within the UDH (you can basically have a UDH consisting of many elements like concat information, sounds / graphic information, etc).

08 - UDHL     - 8 octets

## Informational Element #1

07 - IEI      - UDH Source Indicator
01 - IEIL     - 1 octet
03 - <LF> character

## Informational Element #2

00 - IEI - Concat
03 - IEIL - 3 octets
99 - Concat reference number                - 153
02 - Total Parts: There are two parts       - 2
02 - Part number: This is the second part   - 2

Do take a look at the 3GPP specification mentioned above. More specifically section 9.2.3.24 TP User Data (TP UD). Here it explains with diagrams how the UDH is constructed.

To summarise you need to scan through the Information Elements. And in this case just skip over such Information Elements injected from the SMSC.