Ericsson MINI-LINK TN R3 ETSI Technical Description page 53

Basic Node
In this solution, the ring network can tolerate one failure without losing
transmission. When the failure re-occurs, the affected connections are switched
in the other direction.
In a MINI-LINK TN R3 network, these ring structures can be built using PDH
Radio Terminals with capacities of up to 32x2 Mbit/s, and using SDH Radio
Terminals with the LTU 155 (STM-1 interface) with capacities up to 63x2 Mbit/s.
Capacity is distributed from a common feeder node to the ring nodes where it is
dropped off to star or tree structures as shown in Figure 45 on page 47.
As an example, consider the nodes A and E in Figure 45 on page 47. To protect
the connection from A to E the two alternative connections from A to E must be
defined as a 1+1 E1 SNCP group at A and as a 1+1 E1 SNCP group at E.
Similarly, to protect the connection from A to C, the two alternative connections
between A and C must also be configured as two 1+1 E1 SNCP groups at
A and C.
A
B
F
E
C
D
6629
Figure 45 Example of ring protection with 1+1 E1 SNCP
The 1+1 E1 SNCP function can be used to build protection in more complex
topologies than rings, using the same principle.
47
4/1555-CSH 109 32/1-V1 Uen B 2007-09-14