Call Roaming - Motorola MTP850 S Product Information Manual

54 | Services and Features
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.
For compatibility with systems that do not support type-1 or type-2 cell reselection, the radio can be provisioned to
never perform these types of reselections.
The radio decides on the need for cell reselection, based on comparison of the signal strength and the service level
between the serving cell and neighbor cells. The service level criteria are based on the following criteria listed in
priority order:
1 System Wide Services available (Local/Wide Trunking)
2 Valid/Invalid Subscriber Class
3 Relinquishing criteria
4 Congestion level
5 Security Class
6 Subscriber Class
7 Home Location Area (Home Location area)
8 LA Boundary
9 Cell Load
The radio prefers a cell that has a higher service level to one with a lower service level. If the radio is operating on a
serving cell that has a lower service level than a neighbor cell, the radio roams to the neighbor, even during a call.
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