You don't need any more experiments!

You already have enough experimental data!

You need to work through your received PDUs, one octet at a time, referring to the tables in the links I provided (see the "two most useful" ones).

The tables describe each octet in sequence in a PDU - you just need to work through them, one octet at a time.

You do realise that an "octet" just means an 8-bit group; ie, a byte?

For example, your 1st PDU:


Start by breaking it into octets:


Then just work through rach octet in turn:

1st octet = 06 = Length of the SMSC information (in this case 6 octets)

2nd octet = 91 = Type-of-address of the SMSC. (91 means international format of the phone number)

So the SMSC info contains 6 octets; the first is the Type-of-address (above),
therefore the next 5 octets contain the remainder of the SMSC info; ie, the SMSC address (SCA) - as digit pairs

etc

Check your results by using the decoder provided.

Once you understand how to do this by hand, then you can code it for your 8051...