When MS in a GSM cell obtain the list
of neighboring UMTS cells and cell reselection parameters through System
Information 2ter and System Information 2Quater. Based on the list and parameters,
the MS measures the neighboring UMTS cells. When the MS is in idle mode or packet
transfer mode, the method for cell reselection from a GSM cell to the UMTS cell
is the same as that between GSM cells. The GSM network controls the cell
reselection from the GSM cell to a UMTS cell through TDD Cell
Reselect Diversity.
TDD Cell
Reselect Diversity indicates
the signal strength difference between candidate UMTS cells and the serving GSM
cell. This parameter is a key factor for controlling the cell reselection from
the GSM cell to the UMTS cell.
CPICH RSCP > RLA_C + TDD Cell Reselect
Diversity
When TDD Cell Reselect Diversity is set to a small
value, the cell reselection condition is easy to meet. In this case, the number
of MSs that camp on the GSM cell reduces. When TDD Cell
Reselect
Diversity is
set to a great value; the cell reselection condition is difficult to meet. In this
case, the number of MSs that camp on the GSM cell is increases.