Information Technology Reference
In-Depth Information
192 kbps
(Channel 1,
Channel 2,
Signalling info.
and extra framing bits)
Channel 1 (64 kbps)
Channel 2 (64 kbps)
Ba
s
ic rate ISDN
Data rate:
128 kbps
Signalling information (16 kbps)
Channel 1 (64 kbps)
Channel 2 (64 kbps)
Primary rate
I
S
DN (H11)
Data rate:
1.536 Mbps
1.544 Mbps
(Channel 1..24,
Signalling info.
and extra framing bits)
Channel 24 (64 kbps)
Signalling information (64 kbps)
Channel 1 (64 kbps)
Channel 2 (64 kbps)
Primary rate
I
S
DN (H12)
Data rate:
1.920 Mbps
2.048 Mbps
(Channel 1..30,
Signalling info.
and extra framing bits)
Channel 30 (64 kbps)
Signalling information (64 kbps)
Figure G.2
Basic rate, H11 and H12 ISDN services
The basic rate ISDN gives two B-channels at 64 kbps and a signalling channel at 16 kbps.
These multiplex into a frame and, after adding extra framing bits, the total output data rate is
192 kbps. The total data rate for the basic rate service is thus 128 kbps. One or many devices
may multiplex their data, such as two devices transmitting at 64 kbps, a single device multi-
plexing its 128 kbps data over two channels (giving 128 kbps), or by several devices trans-
mitting a sub-64 kbps data rate over the two channels. For example, four 32 kbps devices
could simultaneously transmit their data, eight 16 kbps devices, and so on.
64 kbps channels multiplex with a 64 kbps-signalling channel, and with ex-
tra framing bits, the resulting data rate is 2.048 Mbps (compatible with European PCM-TDM
systems). This means the actual data rate is 1.920 Mbps. As with the basic service this could
contain a number of devices with a data rate of less than or greater than a multiple of
64 kbps.
For H12, 30
×
64 kbps channels multiplex with a 64 kbps-signalling channel, and with ex-
tra framing bits, it produces a data rate of 1.544 Mbps (compatible with USA PCM-TDM
systems). The actual data rate is 1.536 Mbps.
For H11, 24
×
G.3 ISDN physical layer interfacing
The physical layer corresponds to layer 1 of the OSI seven-layer model and is defined in
CCITT specifications I.430 and I.431. Pulses on the line are not coded as pure binary, they
use a technique called alternate mark inversion (AMI).
