Table of Contents
Advertisement
40 | Services and Features
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.
During network reconfiguration, a significant number of radios registered on one cell may roam. This roaming can
cause major congestion on specific cells. In order to avoid the congestion on control channels for the specific cells,
the specified radios roaming should be distributed in time.
As the operation cannot be performed immediately for all the radios, some of the radios must wait longer to roam.
The time cannot be programmed not to cause any of the radios to have inferior roaming capabilities. Thus the
roaming time for the radios is randomized.
The randomization means that after roaming scenario starts, a radio is not sending registration parameters to other
cells at once but waits random time before sending registration PDUs to other cells. Link failures and other related
scenarios are not randomized not to cause any unwanted delays in restoring the link.
Seamless Handover
Seamless handover eliminates voice interruption during calls by enabling the radio to roam faster between cells while
transmitting. Faster roaming is possible because the radio asks its serving cell to perform the reselection and the
SwMI performs all of the roaming signaling. The radio then moves straight to the traffic channel on the new cell and
continues the call without call restoration.
Air Interface Migration
The Air Interface Migration (AIM) feature enables the radio to migrate to a foreign SwMI, that is, the radio
registration in a foreign SwMI is allowed. The AIM also enables the radio to attach the groups in a foreign SwMI and
to make and receive calls and SDS.
The AIM services cover individual call, group call and individually addressed SDS or Status. In order to receive
group calls or group addressed SDS and Status from a group of the current network, the radio has to attach the
nominated group. The radio cannot migrate to a foreign network while it is in an active call. The radio also cannot
attach a foreign group on the current network hence no group-addressed status/SDS messages can be sent to home
network of the migrated radio. After migrating the radio is in the Clear Mode.
When AIM feature is enabled the radio selects the network in the Foreign Net mode (selectable in the radio MMI).
Foreign Network (Foreign Net)
In this mode radio selects the network automatically where the home network is not available. The radio registers
to any network that it finds that is already programmed into its codeplug list of networks, i.e. no user manual
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 Visiting Short Subscriber Identity
(VSSI).
Send Feedback
| |
Advertisement
Table of Contents
