Specifications

Enhanced Base Transceiver System
iDEN® System
August 08, 2000 68P81095E55-E 2-5
LAN Interface Each EBTS component is monitored and communicates with each other directly or
over a LAN. The LAN interface is the path for traffic flow. The LAN also supports
the Alarm and Messaging monitoring functions (iMU or BMR/EAS). Operations and
Maintenance uses the iMU and the LAN to access the cell site.
The LAN is a thinwire, coaxial Ethernet (10base2) that runs Carrier Sense Multiple
Access/Collision Detect (CSMA/CD) protocol. This allows the BRs and the iSC to
access each other as time and traffic requires with a minimum of control overhead.
BR Antennas
Antennas will vary with each installation. Each EBTS cell requires has a minimum
of one antenna for the radiation and reception of the RF energy that is the Radio
Link. There is usually more than one antenna or branched antennas (Diversity
Antennas).
Functional Characteristics
The EBTS can be configured to support multiple RF frequencies in a omni-
directional or sectored configuration. Major f
unctions of the EBTS are:
• Maintenance of the radio link
• Radio link formatting, coding, timing, error control & framing
• Timing control supervision to subscriber units (time advance)
• Radio link quality measurements — Signal Quality Estimate (SQE)
• Recognition and separation of traffic (Interconnect, Dispatch, Circuit Data or
Packet Data)
• Site-to-site frame synchronization
• Interface conversion - radio link to DS0
• Switching functions between base transceivers
• Operation, maintenance, and administration of Radio Link equipment
The EBTS also relieves the network from the lower level site control functions. This
helps isolate the central network functions and the RF radio link. Because the EBTS
performs most control functions, the number of network messages is minimized.
This results in a shorter call setup time and decreased link control overhead.
Radio Link
Maintenance
The basic wireless radio link is a 64 kbs digital baseband signal subdivided into 6
timeslots. Each timeslot at the cell site is a radio link. The MS constantly analyzes
the quality of the radio link. When the MS and the FNE determine that a better
signal exists and the MSs radio link is processed accordingly.Some of the radio link
functions the EBTS is responsible for include:
• Channel disconnect and failure
• Trolling — contact, position update, and identification of the MS
• Handover — changing to a cell site with a better signal
• Cell selection — choosing a cell to host the MS
• Disconnect and re-connect