I. Group Call

The group call service allows a Mobile Station to initiate a one-to-many communication with a group of users defined by their talk group affiliation. The Mobile Station defaults to group mode operation. It is very easy to make and receive group calls

1. Group Call

-The user can change to talk group selection at any time and the currently selected talk group ID will be shown on the Mobile Station display
-To initiate a call to the talkgroup, the user simply presses the Push-to-Talk (PTT) button
-Traffic channels are assigned to the talkgroup for the duration of the group call.

2. Multi-Group/ Announcement Call

-Provides a valuable extension to the group-call service by allowing announcement calls, which simultaneously include multiple Talk groups.
-The network manger can configure the system with multi-groups, each of which comprises a list of Talk groups

3. Emergency Call

-It is vital for all networks that there is a coherent strategy for handling emergency situations
-The emergency alarm includes the originator’s identity, thus providing the fastest possible notification that the user is in trouble
-The emergency alarm will be detected by all dispatch consoles to which the Talk group of the initiating Mobile Station is assigned

Ⅱ. Individual Call

TETRA supports individual, private communication between two individual Mobile Stations, or between a Dispatch Console and a Mobile Station.

1. Communication between two individual mobile stations (“Terminal to Terminal”)

-Pressing PTT, the system allocates a traffic channel to their private call.
-Receiving Mobile Station will annunciate a distinct tone and the identity of the calling party will be displayed n

2. Communication between a Dispatch Console and a Mobile Station (“Terminal to Dispatch Console”)

-For half duplex individual call, only one party can speak at a time.
-For full duplex individual call, user can transmit and receive simultaneously

Ⅲ. Telephone Interconnect Call

1. Telephone Interconnect Call

-A telephone interconnect gateway to permit connections between a Mobile Station and customer provided PABX/PSTN telephone network
-The Network Manager can select which Mobile Stations are enabled for Telephone Interconnect services

Ⅳ. Handover

1. Handover

Terminal, belonged to base station, implements auto roaming to sense stronger RF signal which the nearest base station serves for the purpose of seamless communication.

-When terminal reaches to B from A base station, automatically it senses stronger frequency and contacts better ones.

Section	Description
Cell Selection	-If a terminal registered to a base station, the base station will transit cell frequency and signal to decide handover decision
Handover Preparation	-The RSS value of the current base station initiates processing handover if parameter value is less than critical index.
Handover Start	-Cell C2 signal and cell C1 will be increased as SRH value, and start new cell C2 handover.