Wireless Future - Telenor

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X:User
1:Device
2:Device
3:Device
Figure 9 Initiating service
from an IP-based device
ISUP
PSTN/ISDN
Gateway
ISUP
Gateway
Gateway
Mobile Network
In order to realise the Use Case Initiating Service
the following conditions must be met:
• Every object Virtual Terminal must have an
identity that is visible to all devices, i.e. it
should be possible to address the Virtual Terminal
from any device. Each Virtual Terminal
may have several identifiers:
- An MSISDN number (telephone number);
- An email address;
SIP/H323
IP-based
Network
A:Service
X:Virtual
Terminal
- Some kind of unique identifiers conformed
to OSA/Parlay [7,8].
If the Virtual Terminal has several identifiers,
a mapping between these identifiers is required.
• It should be possible to establish a connection
from any device to the Virtual Terminal and a
connection from the Virtual Terminal to any
service or any other device. The Virtual Terminal
must be capable of acting as a connector
that connects the streams together.
The user may have different devices connected
to different networks. One device can be an IP
phone or a PC directly connected to an IP-based
network, another device can be a fixed phone or
cordless phone connected to the PSTN/ISDN
network, and a third device can be a cellular
phone connected to a mobile network such as
GSM.
The protocols used to establish and terminate a
connection vary for different networks. For IPbased
networks either SIP [9] or H323 [10] protocols
should be used but for PSTN/ISDN and
mobile networks, the protocol is SS7 ISUP.
When the user initiates a service from a chosen
device a connection must be established from
this device to the Virtual Terminal. Different
protocols should therefore be used depending on
the type of device, i.e. IP-based device contra
PSTN/ISDN or mobile device.
Let us consider these two device types successively.
6.1.1 Initiating Services from an
IP-based Device
If the user uses a device that is connected to an
IP-based network, either SIP or H323 protocol
is used for signalling. In addition, information
on the requested service or device must be conveyed
to the Virtual Terminal so that it knows
which service or device to connect to. This case
is illustrated in Figure 9.
Two implementation alternatives are identified:
Alternative 1:
• Use SIP/H323 for establishment of connections.
• Use CORBA/Java RMI for control and information
exchange with the Virtual Terminal
[11,12].
Alternative 2:
• Use OSA/Parlay API for establishment of
connections.
• Use CORBA/Java RMI for control and information
exchange with the Virtual Terminal.
The most straightforward implementation will
be to incorporate either SIP or H323 in the Virtual
Terminal. However, such a solution does
not imply portability since the code of the Virtual
Terminal needs to be changed for each protocol.
A better solution might be to use OSA/Parlay
API since a generic and network independent
Call control API is offered. Portability is hence
ensured and the Virtual Terminal will function
on either SIP or H323.
6.1.2 Initiating Services from PSTN/ISDN
or Mobile Devices
If the user uses either a device connected to the
PSTN/ISDN network or a device connected to a
mobile network such as GSM, the SS7 ISUP is
used to establish connection.
Assume that a user wants to make a telephone
call to another phone. He dials the number of the
addressed phone. The signalling must somehow
be routed to the Virtual Terminal, and there is a
need for an IN service, which sends the signalling
to the Virtual Terminal. This IN service
Telektronikk 1.2001