Specifications

Functions
Interconnect Call Processing
5-2 68P81095E55-E August 08, 2000
General
Interconnect calling allows an MS to travel freely throughout an iDEN system and
teamed roaming partners. Within this extended network, a user can originate or
receive interconnect calls. The systems track the MS's location and services as well
as route the calls. With networked regions the MS can roam into those interconnected
regions originating and receiving calls as if the MS is in its home system.
Figure 5-1 shows the major elements involved in Interconnect calling. The MS sends
and receives voice data. The EBTS converts the radio link to the land link and
discriminates between Interconnect and Dispatch calls. The BSC routes interconnect
packets between the EBTS and the MSC. The MSC determines services and location
information. The MSC also controls and routes the calls to other providers.
Figure 5-1 iDEN Interconnect Call Elements
The control and monitoring steps needed to complete this task are primarily internal
to the iDEN system. Aside from dialing sending and receiving, the steps to complete
an Interconnect call are user transparent. There four major steps in an Interconnect
call:
• Establish Radio Link
• Route digital voice packets
• VSELP/Mobis — PCM/SS7 conversion
• Other network routing
Establish Radio
Link
The radio link is the on-air connection. This is a coordinated effort between the MS,
EBTS, BSC and the MSC. The RF Subsystem analyzes the MS broadcast and
determines the EBTS to host the call. The BSC routes the call setup information to
the MSC. The MSC queries the HLR and VLR to determine location access,
authentication and service availability. The EBTS establishes and maintains the
radio link. This includes coordination of handoff to another EBTS if the MS’s
location indicates another EBTS has better radio link quality. Setup, control and
monitoring of the radio link uses the Mobis link protocol.
Route Digital Voice
Packets
Once the radio link is established, the EBTS discriminates between a Dispatch call
and a Interconnect call. The DAC will cross-connect interconnect voice packets to
the BSC. The BSC coordinates the movement of packets between the DACs and the
MSC. The BSC re-routes calls to another EBTS on handoff. Control of the link
between the BSC and the MS use the Mobis protocol. Control of the BSC/XCDR
complex and the MSC link uses SS7 routing and messaging.
HLR VLR
Mobile Station
(MS)
RF
DAC
(span
connections)
iSC
ACG
iMU
BSC
(routing and
conversion)
XCDR
MSC
(services &
PSTN routing)
EBTS
(radio link)
T. N .
French
T. N. French
IWF SMS
Fax/Modem
Bank
External,
online
messaging