What kind of communication stanard is this

I am new to to smart meters, I was recently checking out a smart meter system, the gateway is a esp8266 which communicates to the data collector over mqtt with some hex format. other meters connects to the gateway meter with some sort of rf mesh NAN with 32 bit meter address similar to ipv4. the data collector publish to the topic with the name of the grid id of the gateway meter. the gateway meter subscribed to the topic sends it to the appropriate meter and gets the result of the commands and publish this data in hex format in a common topic with the grid id at the last to determine which gateway meter has responed. I would like to know what kind of communication protocol is being used here. I am giving more details below

Every frame starts with a preamble 0xAA

command from data collector to the meter on the topic of the name with gateway serial no:
aa1b 2738 ca05 0025 1d04 0403 2738 007d 83

from what I understood, here 1b is transaction/packet id , 2738 is the command and 05 00 25 1d is the meter address -> 5.0.37.29

now the reply from the gateway is :
aa05 0025 1d1b 2738 ca04 0406 f003 6514 babb b8cd 0000 7913
05 00 25 1d --> meter address
1b --> paket id, reply to this id
2738 --> command
6514 babb --> time stamp in unix format
7913 --> which is the gateway id by which the data collector filter out from which gateway the response came from as all gateway publish the response over the same topic.

The type of meter is a dlms based meter, I am not able to figure out what kind of communication is this, it is not similar to m bus or hdlc which are commonly used.

I would appreciate any help for figuring out what protocol is this

thanks,
pickle