Network

PTT Express allows 63 users to communicate across a single sub-net. The Group Broadcast feature only permits a single user to transmit to the other members of the Talkgroup at a given moment in time. Additionally, it is assumed that at most half of the Talkgroup members (that is, approximately 32 users) are served by a single access point. As members in the Talkgroup reply via the Private Call feature, they may communicate privately to one another and Group Broadcasts may continue.

PTT Express Communication has been designed to minimize end-to-end audio delay. However, audio delay may be up to two seconds or more depending on conditions of the network.

Each device is configured to transmit to and receive from this address. Table 1 provides the default value for this address 'ipBroadcastGroup', along with the 'ipBasePort' (Group Broadcast port) that is required to be available on each device. These values may be modified from their default values as described in Android Configuration File Settings section, but each device in the group must be configured with the same values for the parameters. The PTT Express client Private Response communication utilizes SIP (Session Initiation Protocol) for call signaling and sends audio packets via unicast transmissions between the devices in the Private Response. The ‘sipLocalPort’ (SIP Private Response port) must be the same value on all devices.

The PTT Express client Private Response communication utilizes SIP (Session Initiation Protocol) for call signaling and sends audio packets via unicast transmissions between the devices in the Private Response. The PvtLocalPort (SIP Private Response port) must be the same value on all devices.