2 Communication organization in the sdh ring

2.1 Levels of the synchronous transport modules in sdh ring

It is known that for constructing the nodes as elements of transport network SDH, in addition to synchronous multiplexers (terminal, linear, highlight/paste) is applied AOP or digital system operational cross-connections DXC (digital cross-connectors).

Under the operational switching or cross-connection should be understood to establish the semi-permanent network connections between different digital channels. It is appropriate to note the difference between the operating switch and the switching. The latter involves the establishment of a temporary connection in the secondary network on the initiative of subscribers. In the case of operational units of semi-permanent cross-connections are established by commands of the operator network using network management tools.

Levels of the synchronous transport modules in SDH ring.

Table 2.1 – Traffic in the SDH ring

	1	2	3	4	5	6	7	8	10
1	-	21	21	21	21	21	21	22
2		-	21	21	21	21	21	24
3			-	21	21	21	21	14
4				-	21	21	21	14
5					-	21	21	19
6						-	21	18
7							-	21
8								-	28
10									-
Q	148	150	140	140	145	144	147	132	∑ NDNN =622

To determine the level of STM need to build multiplicy plan in normal operation and during accidents protection method – SNCP/BР/1+1/2ОF.

SNCP 1+1.

This method differs from SNCP 1:1, in this case transmission is carried out simultaneously both through the main and reserve channels, and the receiving part chooses a signal with the best quality (which, in fact, is the basic, the second is according to the reserve). During the failure mode one of the transmission directions disappears, and communication between network nodes is provided in the remained direction similar to the SNCP 1:1 scheme (see fig. 2.2). Each of streams transmitted through a ring loads all the sections (working or reserve channel), i.e. hierarchy level calculation is reduced to the determination of the total number of streams in a ring. So, this method differs from the other in that for the definition of hierarchy level it is not necessary to build the multiplexing plan, it is quite enough to summarize streams according to the table of inter-nodal network traffic NΣPDS.

Figure 2.1 – Multiplexing plan of SDH ring work in normal operation mode

for SNCP/BP/1+1/2ОF.

Figure 2.2 – Multiplexing plan of SDH ring work in emergency operation mode for SNCP/BP/1+1/2ОF.

We determine the level of STM using multiplex plan in normal operation given the conditions:

63≥ N_DNN -STM-1

64≤ N_DNN ≤254 -STM-4

255≤ N_DNN ≤1008 -STM-16

N_DNN = 622

Select the level of STM is determined by the maximum loaded section in normal operation, and we have to choose STM-16 which bitrate equals to 2488,32 Mbit/s.