MT90220
8.0 Application Notes
Inverse Multiplexing for ATM (IMA) divides a high-
bandwidth stream of ATM cells in a round-robin
fashion and sends them over grouped T1/E1 lines in
a logical connection (on public or private networks)
and recombines the cells to recover the original high-
bandwidth stream at the receiving end. MITEL’s
MT90220 is ideally suited to implement the IMA
function.
8.1 Connecting the MT90220 to Various T1/E1
Framers
Many off-the-shelf T1/E1 framers require the
generation of a 1.544 MHz (T1) or 2.048 MHz (E1)
transmit clock reference signal at an input pin. The
MT9042 can generate both these clocks and the ST-
BUS back-plane signals (C4,F0). Figure 19 provides
an example of PCM Modes 2 and 4 in an IMA
implementation using existing T1/E1 framers and a
common 2 Mbps ST-Bus backplane.
New generation MITEL framers only require the ST-
BUS 4.096 MHz (C4) clock and a Frame Pulse (F0i)
at the transmit interface. An internal PLL generates
the required 1.544 MHz (T1) or 2.048 MHz (E1)
transmit clock. Figure 20 provides an example of
PCM Modes 2 and 4 in an IMA implementation
based on the MITEL MT90220 and the MITEL
MT9074 framers. This configuration supports CTC
mode. Although the MT9074 use the ST-Bus format
but it is not configured as a common backplane.
Figure 21 exemplifies PCM Modes 2 and 4 in an IMA
implementation supporting the asynchronous link
operation mode. Each T1 or E1 framer uses
independent clock and synchronization signals which
corresponds to ITC mode.
Figure 22 exemplifies PCM Modes 1 and 3 in an IMA
implementation supporting the asynchronous link
operation mode. Each T1 or E1 framer uses
independent clock and synchronization signals.
Figure 23 exemplifies PCM Mode 5 and 7 in an IMA
implementation supporting the asynchronous link
operation mode where the TXCLK signal is provided
by the T1 interface. Each T1 framer uses
independent clock and synchronization signals.
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MITEL [ MITEL NETWORKS CORPORATION ]
