Here write in simple words how UE select suitable cell in LTE.
After the UE has selected a PLMN, is a done selecting cell â€“ in other words, looking for an appropriate cell camp. While camping on the cell, and that is the UE acquires broadcast. Subsequently, the UE recorded its presence in the area, after which they may receive paging information that is used to notify the UEs of incoming calls. The UE can establish a connection to the RRC, for example, to establish an appeal or to make a tracking area update. When they camped on a cell, the UE regularly check whether a cell is better; This is known as high-performance cell reselection.
LTE cells are classified according to the level of the UE to obtain services on them: a suitable cell is a cell that the UE get normal service. If the UE is unable to find a suitable cell, but manages to camp on a cell from another cell PLMN is said to be an acceptable and UE cell enters a "limited service" State, you can only make emergency calls (and receive a public warning) â€“ as is also the case when neither the USIM is present in the UE. Finally, some cells may indicate through them and that they are prescribed or reserved; The UE can get no service on such a cell.
A category called "service operator" is also supported in LTE, offering normal services, but only applies to UEs with special access rights. The figure provides a high-level overview of the State of the cell (re) selection procedures.