Prodys PortaNet, User Manual

Page: 116 / 156

PortaNet User Manual 116 of 156
As many receivers as required can join this multicast address and receive the
audio, without any increment in the required bandwidth, given that this
communication is based on IP multicast technology.
IX.9 PortaNet operating as an ISDN codec
The PortaNet as ISDN codec is very similar to the Pronto 3, therefore those users
that are familiar with the Pronto 3 will find it easy to operate the PortaNet over
ISDN.
The most important points that a user must have in mind for this mode are as
follows:
1.
ISDN interface:
The ISDN interface of the PortaNet allows
connection to a basic rate ISDN line. This interface allows the user two
bi-directional channels with a bandwidth of 64 Kbps on each direction.
There is an additional channel of 16 Kbps that is used for signalling.
This is why a basic rate connection is sometimes represented as 2B+D.
The PortaNet identifies each B channel as Line 1 and Line 2
respectively.
The PortaNet can operate as “DUAL CODEC”, which means it can
establish two totally independent MONO communications via each B
channel at 64 Kbps. In this situation the PortaNet will be able to use
two Encoders and two Decoders independently.
PortaNet is aimed to work as a MONO codec. To configure the unit to
work as a STEREO codec please read the chapter XI - Operation
Examples.
4.
Communications at 128 Kbps – Inverse Multiplex:
Certain algorithms permit the compression of the signal at bit-rates other
than 64Kbps, for example at 128Kbps. With the PortaNet it is possible to
send or receive audio compressed at 128 Kbps using both the B channels
of the basic rate ISDN connection. This is done by using ‘inverse multiplex’
techniques that split the transmission of the full 128 Kbps over two
channels of 64 Kbps and then sum the parts together again at the other
end.
Inverse Multiplex is often known as ‘bonding’. PortaNet supports
CCS, Telos and J52 bonding algorithms over ISDN
.