System information

FCD 901 48

Issue R2A, 07.2009

XMP1 Release 5.5 System Description

Clock control for co-channel radio operation

Page 2-18 Proprietary Information Aastra

2.3.5 Clock control for co-channel radio operation

For transmitting co-channel radio signals or ripple control signals, a

constant delay time is required for the corresponding channels.

For this purpose, the delays in the elastic memories of the ports must be

kept constant. This is achieved by linking the transmit frame of the network

node phase-rigidly to the receive frame of the ports to be used for

transmitting co-channel radio signals.

In a network node, not only the frequency but also the phase position of the

transmit frame to the port providing the clock is controlled in such a way that

even after signal interruptions or voltage failures, the initial phase relation is

restored. Thus, the required constant delay time is achieved due to the

constant phase relation.

With a stable network status, the phase positions of all ports concerned are

measured in relation to the transmit frame and stored in the node. If in case

of later network failures, the clock is recovered from another port, the initial

phase relation can nevertheless be restored.

Note:

In the initial version (prior to 1995), only one clock tree to be permanently

configured by the user was possible in phase rigid operation (clock priority

0).

Figure 2.7: Clock control in co-channel radio transmission

SYN

GWF

port

Node 1 Node 2

SYN

Node 3

Co-channel radio

transmission (GWF)

Co-channel

radio transm.