Specifications

Interface Protocols
Operating Characteristics
August 08, 2000 68P81095E55-E 3-3
X.25
The X.25 protocol is used primarily in the Operation and Maintenance functions of
the network. The X.25 link is used by the Operation and Maintenance Link (OML)
and its functions between network devices linked to the OMC. The OMC uses X.25
- Link Access Protocol -B-Channel (LAP-B) and Link Access Protocol - Data (LAP-
D). The LAP-D protocol is used in signalling as the Message Transport Protocol
(MTP) between the EBTS and the BSC. LAP-B is the protocol used between the
BSC, the MSC and the OMC. The BSC handles the translation between LAP-D and
LAP-B. X.25 functions primarily at 19.2 kbps on V.35 cables (including the DAP).
The T-DAP uses an Ethernet link but maintains X.25.
Ethernet
The principle use of Ethernet in the iDEN system is between components in the
EBTS. The EBTS uses Ethernet for traffic and control by running Carrier Sense
Multiple Access/Collision Detect (CSMA/CD) protocol. Transmission Control
Protocol/Internet Protocol (TCP/IP) is supported in the Ethernet environment in
accordance with IEEE 802.X. TCP/IP may be used to communicate with the
Administration and Data and other service provider equipment. The TDAP - OMC
interface is Ethernet running X.25 protocol.
Simple Network Management Protocol
Simple Network Management Protocol (SNMP) is used over the dedicated links
between the EBTS and BSC. SNMP is used within the X.25 OML to manage the
alarm, messaging, control and performance data routing to the EBTSs.
Vector Sum Excited Linear Predicting
Vector Sum Excited Linear Predicting (VSELP) protocol is a voice compression
method used in the mobile station and the XCDR. The MS compresses voice for all
transmits and decompresses on voice on all receives. The MPS-DAP cluster controls
the movement of VSELP packets between EBTSs during Dispatch calls. The BSC-
XCDR converts VSELP to Pulse Code Modulation for interconncet calls.
Frame Relay
The iDEN system supports Frame Relay protocol during Dispatch communications.
Depending on how the EBTS is configured for Interconnect and Dispatch, the
number of DS0s available will vary. The iDEN system engineering staff provides
guidelines to allow service providers to provision the T1/E1s for interconnect and
dispatch.
Link Access Protocol-Data (LAP-D) is used between the EBTS and the MPS-DAP-
APD cluster.
The Advanced Packet Duplicators (APD) and iSC are linked using Frame Relay -
LAP-D on a V.35 link. This is an indirect link through the MPS. The speed is at least
256 kbps from the DAP to the MPS, and is set by the MPS. The T-DAP uses High
Speed Serial Interface (HSSI) to interface to the APDs.
Pulse Code Modulation
Pulse Code Modulation is the telephone industry standard for the format and
encoding of data packets transmitted across voice networks. PCM is used by iDEN
for interconnect calls to land networks. The MSC and the BSC XCDR use PCM for
voice and data transmission. The XCDR converts between PCM and VSELP.