Specifications

Functions
Interconnect Call Processing
August 08, 2000 68P81095E55-E 5-7
Interconnect Call Types
Mobile Stations on the iDEN system can complete Interconnect Call with other
providers networks in three basic ways:
• Mobile to other network (PSTN)
• Other Network (PSTN) to Mobile
• Mobile to Mobile
Mobile to Other
Network
On MS power-up, number entry, and call initiation, the MS sends a service request to
the EBTS. The EBTS/BSC/HLR identifies an Interconnect call and routes the
request to the MSC through the BSC.
When the MSC receives the service request, it queries the HLR and VLR for service
access, service availability and MS authentication.
When authentication of the MS is complete, the BSC cross connects the RF channel
to the land-based circuit as soon as it is assigned by the MSC. The MSC assigns the
trunk according to the provisioning of the networks. The MSC then connects the
BSC land circuit to the PSTN trunk.
When the connect to the PSTN is complete, the remote PSTN will request that the
local MSC transmit the dialed digits for the call. The remote PSTN will verify
service and the called party and send a cut through supervision (the called party
answering or a supervisory tone like a busy signal). The MSC will send a connect
message to the MS that allows the MS to receive and transmit voice frames -
completing the call connection.
Other Network To
Mobile
When an incoming call is received at the MSC in SS7 protocol, a channel to the
remote PSTN is allocated and the DTMF digits (dialed number) is received by the
MSC. The MSC will query the HLR and VLR databases to verify the dialed number
exists and to alias the dialed number to the MS (IMSI or TMSI).
The MSC will locate the MS using the Interconnect Location Area (ILA) in the VLR
to page the MS. The ILA is used by the BSC to route the call to the most likely set of
EBTSs using Radio Link Protocol (RLP).
The MSC will wait for the MS to respond to the page. If the MS or resources are
unavailable, the MSC will generate the appropriate status return to the remote PSTN
(busy or out-of-service). If the MS and resources are available, the MSC will
connect the external trunk to the controlling BSC. The BSC will connect the PCM/
SS7 link with the appropriate EBTS span line (T1). The EBTS will establish the
radio link, allocate a radio channel and transmit a hail (ring the phone).
When the user responds, the BSC/XCDR converts the PCM voice packets to the
VSLEP packets used by the radio link. The DAC and BSC completes the cross
connect between the radio link and the other provider land-line to complete
connection of the call.
The MSC may also route the call to the Voice Mail system or to Call Forwarding if
the service is provisioned for the MS and the MS is eligible for the re-route.