In an actual network, not all the BTSs
or cells are busy and not both the PS and CS services have a high traffic
volume at a specific time. Generally, if the load of one BTS is heavy, the load
of other BTSs is light; if the traffic volume of the PS service is high, that
of the CS service is low,
and vice versa. Flex Abis (Flexible
Abis) enables the sharing of the Abis interface transmission resources among
different BTSs, cells, and services, and thus improves the resource
utilization. Flex Abis is a mode of allocating the Abis interface transmission
resources. That is, the Abis interface transmission resources form a resource
pool that is shared by the CS service and PS
service (including idle timeslots)
among different cells and BTSs.
The Abis interface transmission
resources can be used more effectively when Flex Abis applies to the following
cases:
·
Multi-cell large-capacity BTSs
·
Cascaded BTSs
·
EGPRS
capable cells
The transmission resources over the
Abis interface can be allocated either fixedly or dynamically.
·
Fixed allocation mode
:
In fixed allocation mode, the channels
over the Um interface (including the TCH and static PDCH) are always mapped
with the Abis interface transmission resources. That is, the Abis interface
transmission resources are occupied even when the Um interface channels are idle.
·
Dynamic allocation mode
In dynamic allocation mode, the Abis
interface transmission resources form a pool. The Abis interface transmission
resources are allocated to the Um interface channels only when the channels are
occupied. Thus, the Um interface channel resources can be much more abundant
than the Abis interface transmission resources, and the Abis interface transmission
resources can be fully utilized in different time slices. Flex Abis features
the dynamic allocation of Abis interface transmission resources,
which improves the utilization of the
resources, as shown in
