23.0423GPPCompression algorithm for text messaging servicesRelease 17TS
Character Group ID 0 (decimal)
This Character Group ID has the special meaning that no Character Group is defined (or therefore enabled) and the value of bit 0 of octet 1 of the CH is always to be interpreted as zero.
Character Group ID >0 (decimal)
No other Character Groups are defined and all other values are reserved.