User's Manual

SME VoIP System Guide, Version 1.5
Proprietary and Confidential
Chapter: Network Operations
104
15 Network Operations
15.1 Introduction
In this chapter, we will provide an overview of the operation of the network during system start-up,
location registration and speech calls including illustration of different call scenarios.
15.2 System Start Up
When a Base station Unit is powered up, it achieves IP address from DHCP server and time from the Time-
Server.
Optionally the base retrieves its configuration from a file on the TFTP server. This configuration file
describes used network and cluster configuration parameters (optional and not needed).
The SME VoIP network has successfully started up.
15.3 Terminal Attachment
When a DECT Terminal (also called handset or SIP node) is turned on or moved into the coverage area of a
Base-station it has to get attached to the network. When more Base-stations are available, the Terminal
selects the one with best RF signal. This procedure, called Location Registration, always keeps the network
informed about where a Terminal is located and enables it receive or originate calls. This procedure also
authenticates the Terminal and checks the validity of the associated subscription.
15.4 Outgoing Calls
Outgoing calls are initiated by the Terminal. It selects the Base-station with best RF signal and establishes a
radio communication link to Base-station. DECT call control messages are exchanged between Terminal,
Base station and other servers. This server forwards the outgoing call as SIP messages to the external SIP
Server. The RTP stream is established between the involved Base-station (and the Media Gateway for PSTN
calls). If the call is between two Terminals the media stream may be routed directly between the two
involved Base-stations depending on the SIP Server routing strategy.
15.5 Incoming Calls
Incoming calls are initiated by SIP INVITE messages from the SIP Server to the Base unit; inviting it to
participate in an incoming session. The system sends paging messages to all the Base-station where the
Terminal last performed a Location Registration. When the paging is received the Terminal establishes a
radio communication link to the best available Base-station and sends a response back to DECT controller.
DECT call control messages are exchanged and the Terminal starts ringing. When the user answers the call,
a connect message is sent to the IP DECT controller that completes the incoming call by sending 200 OK
back to the SIP Server and establishes an RTP media stream between Base-station (and Media Gateway
from PSTN line). For internal calls the media stream may be routed directly between the involved Base-
stations.