5.3 Cell Reselection

The cell reselection can be controlled either autonomously by the mobile or by the network. It is based on measurements performed by the mobile. The network can order that these measurements be reported periodically.

Three cell reselection modes NC0, NC1, and NC2 have been defined:

• NC0. In this mode, the GPRS mobile performs autonomous cell reselection without sending measurement reports to the network.

• NC1. In this mode, the GPRS mobile performs autonomous cell reselection and periodically sends measurement reports to the network.

• NC2. In this mode, the network controls the cell reselection. The mobile sends measurement reports to the network.

When the mobile performs autonomous cell reselection, it chooses a new cell and triggers a cell reselection on its own. The NC2 mode allows the network to control the mobility of GPRS users within the network.

The GPRS cell reselection mode for a GPRS-attached MS is given by the network control mode (NETWORK_CONTROL_ORDER parameter), which is broadcast on the BCCH or PBCCH. The mobile behavior is determined by both its GMM state and the network control mode. Whatever the value of the network control mode, when the MS is in GMM STANDBY state, it performs autonomous cell reselection and does not send measurement reports to the network. In GMM READY state, the mobile performs cell reselection according to the network control mode.

Two criteria are defined for autonomous cell reselection: one is based on the (C1, C2) criteria. It corresponds to the GSM cell-reselection...