What is the packet domain service?

I came across the phrase “packet domain service” in de BC660K-GL AT commands manual. Does anyone know what this means? I can’t find anything else about it in the manual, and a google search yields no relevant results.

Furthermore, in the same text “PS” is also mentioned a few times. However it is not explained what this means in the abbreviations sections at the end of the manual. Does PS maybe refer to Package Switch Domain (PSD)? If so, why is the abbreviation PSD not used?

Many thanks!

24301-h20.pdf (8.6 MB)
please refer to 3gpp