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Data Transmission TechnologiesFeatures of the SDH line of microwave systems

SDH technology is not limited to use as a transmission medium, only the fiber-optic cable (FOC). Also, widespread use of radio for the organization of radio relay line SDH networks. Relay channels have great promise for replacing relay RDN systems, the possibility of more effective interaction with the existing SDH systems, optimization of networks SDH circuits in the complex for laying FOC areas of organization of alternative SDH signal transduction pathways and backup of the existing fiber-optic SDH lines.

Manufacturers MRR


  1. Microwave radio relay system SDH «96xx», which includes the following modifications:
    1. LH - system level STM-1 with long inter-station sections;
    2. UH - system level STM-1 for use in an urban environment;
    3. LM - system level OC-1 for use with the access networks;
    4. UM - system level OC-1 for use in urban environments.
  2. The transport relay system "9667 TH» STM-1 level;

ECI: radio-relay systems SDH «SDH-Radio» level STM-1 and STM-4;

NEC: SDH radio relay signaling system level STM-1 signals or PDH E4.

Data Transmission TechnologiesEthernet over SDH

Sept. 3, 2015, 4:19 a.m.


Ethernet and SDH technologies are focused on computer and information networks. But the main problem in their interaction is pairing constant fixed speed SDH channels with pulsating Ethernet traffic. For example, VC-4 has a speed of 149.760 Mb / s, while Ethernet 100Base-T has a speed of 100 Mbit / s, respectively. Thus SDH payload channel is 70%, whereas the payload transmission GigabitEthernet generally drops to 40%. To solve these problems using technology GFP, VCAT and LCAS. In fact, these procedures have formed SDH network of the New Generation (NG SDH). Many network operators are given the opportunity to upgrade their networks instead of complete replacement of existing equipment.

Data Transmission TechnologiesSDH - Synchronous Digital Hierarchy (Part 2)

Aug. 8, 2015, 3:49 a.m.


Compensation of frequency synchronization error

The pointer can not only fulfill a fixed phase shift and mismatch clock multiplexer clocked device, from which the user data is received. To compensate for this effect, the index value is periodically incremented or decremented.

Positive alignment - The pointer is incremented by one, reflecting the delay start of the next container VC-4, three bytes.

Negative alignment - to accommodate the "extra" bytes used three younger byte pointer, ie the NT box (the pointer itself fits in fields H1 and H2)

Data Transmission TechnologiesSDH - Synchronous Digital Hierarchy (Part 1)

Specific technologies PDH deficiencies have been addressed and overcome technology developers synchronous optical networks (Synchronous Optical NET, SONET), the first version of the standard which appeared in 1984. It was then standardized Committee of T-1 ANSI Institute. As a result of long work ITU-T and ETSI managed to prepare an international standard SDH (Synchronous Digital Hierarchy - Synchronous Digital Hierarchy).

The main goals of SDH developers were:

  • Continuity of existing digital channels T1-T3, E1-E3
  • Ensuring the hierarchy of speeds far exceeding the speed of plesiochronous digital hierarchy (PDH)
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