Handoff

CDMA2000, whether implemented as 1x only or a 1x/3x environment,
needs to have the capability for handoffs and hangovers to exist in the system
either between similar systems or legacy systems. Numerous decisions
need to be made by the design engineer besides channel assignment
schemes. The issue of how a handoff or hangover takes place within the system
has a profound impact on the system performance of the network and
obviously the subscriber’s view of their service.Table 5-9 best illustrates the
interaction between different traffic channel types in SR1 only.
The same types of handoffs occur with CDMA2000 as they do with IS-95
systems with the exception of packet data situations. The types of handoffs
involved with CDMA2000 are as follows:
■ Soft
■ Softer
■ Hard
In addition to the handoff situations with a mixed network listed in
Table 5-9, CDMA2000 systems can also interact with AMPS analog channels
like IS-95 systems by performing a hard handoff. Obviously, if a packet session is in place, the packet session will be lost and will be lost anytime
the source channel is downgraded or if the mobile transitions out of the
PSDN’s effective coverage area.
Many scenarios are possible with CDMA2000-1x and legacy systems
that are directly dependant upon the CDMA2000 system deployment and
the logical BSC and PSDN boundaries that are established. To further add
to the mix of possibilities, the BTS can also force a subscriber unit to a lower
RC when
■ The resource request is not a handoff
■ The resource request is not available
■ Alternative resources are available