Cell reselection

While camped on a cell of the registered PLMN ("camped normally"), the MS may need to select a different cell ("normal cell reselection" state). The following events trigger a cell reselection:
i) The path loss criterion parameter C1 (see subclause 3.6) indicates that the path loss to the cell has become too high;
ii) There is a downlink signalling failure (subclause 3.6);
iii) The cell camped on (current serving cell) has become barred;
iv) There is a better cell (in terms of the path loss criterion C2) in the same registration area, or a much better cell in another registration area of an equivalent PLMN (using the CRH parameter, subclause 3.4);
v) A random access attempt is still unsuccessful after "Max retrans" repetitions; "Max retrans" being a parameter broadcast on control channel;
vi) Upper layers have determined that the network has failed an authentication check (see subclause 3.5.5).

Ref: 03.22 - sec 4.5