Where can I find detailed information about the LTE PRACH Restricted Set (Hight Speed Case)

4G LTE
1

Hi.

Is there any good article or note explaining restricted set (A and B) for the short and long preamble?

2

If the UE transmits a Group A preamble then the eNodeB selects a short payload size, whereas if the UE transmits a Group B preamble then the eNodeB selects a long payload size.

Selection of group A means chanel quality is bad
Selection of group B means chanel quality is good

UE can always select a Group A preamble if the Random Preamble group A Size equal random preamble.