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selection is required. Network selection to another network is only performed at initial cell selection following a
link fail and then only if the home network is not available. The radio uses its own ISSI.
The radio operates in all networks as it does in its home network. All calls are placed using SSI addresses, and it is the
SwMI responsibility to reject calls for subscribers or groups that cannot be reached in the local system.
Note: The telephony gateway interprets telephone numbers with the country code of the local country. For
example, if you dial the number 01256-48-4566 in the UK, it is treated as if you dialed +44-1256-48-4566.
For description of other migrating modes used when migration is supported by the BTS, refer to Air Interface
Migration and Dynamic Air Interface Migration sections.
Registration
On camping on a cell, the radio sends a registration request PDU to the SwMI, which includes a request to attach to
the selected talkgroup.
If the registration and attachment succeeded, the radio begins normal operation on the cell. If the registration attempt
times out, or the SwMI rejects the registration for a temporary reason, another registration attempt is made. If both
attempts fail, the radio attempts to camp on a different cell.
If the SwMI denies the registration request due to the location area rejection, the radio does not attempt to register
again at this cell until the next power-on. The radio supports the modification of its subscriber class on receipt of a
new subscriber class from the SwMI in the registration acknowledgment PDU. This subscriber class is used until
turning off the radio or next ITSI attach.
The radio does not send registration signaling when one of the following occurs:
•
Roaming and registration fail before the radio receives the random access acknowledgment and the radio goes
back to the last serving cell.
•
The radio discovers a link failure on the serving cell, the link failure is shorter than the predefined timer and the
radio is not in the transmit inhibit mode.
•
The radio discovers a link failure on the serving cell and is in the transmit inhibit mode. In this case the radio
always goes back to the serving cell without registration and stays in the transmit inhibit mode until the mode is
turned off.
Note: When two or more scenarios occur at the same time, the radio registers with signaling.
If the radio discovers a link failure on the serving cell, a specific timer starts counting. If the link failure remains after
the timer expires, then the radio acts as during a normal link failure. If the link failure ends before timer expires, then
the radio goes back to the serving cell without registration. This mechanism ensures that unnecessary registration is
avoided.
When a radio is out of the serving cell range for a period shorter than configured in the codeplug, then the radio does
not perform the registration on going back in the range.
Call Roaming
The radio continually monitors neighbor cells and scans the highest ranked neighbor cell. When the state of the
highest ranked neighbor cell is sufficiently better than the serving cell, or when the radio has lost the serving cell, the
radio employs cell reselection procedures using the following methods:
•
If not in a call — undeclared cell reselection.
•
If in a call and not transmitting or link failure occurs — unannounced cell reselection.
•
If transmitting in a call, and a neighbor has been scanned, and the cells are synchronized — announced type-1 or
type-2 cell reselection.
•
If transmitting in a call and no neighbor has been scanned or the cells are not synchronized — announced type-3
cell reselection.
Services and Features | 39
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