Huawei SDH transmission equipment Optix Metro1000 V3 adopts a hierarchy of information structure called synchronous Transport Module STM-N (Synchronous Transport Mode, N=1, 4, 16, 64), the most basic module is STM-1, four STM-1 synchronous multiplexing constitute STM-4, 16 STM-1, four STM-1s synchronously multiplexed to form STM-4, 16 STM-1s or four STM-4s synchronously multiplexed to form STM-16, four STM-16s synchronously multiplexed to form STM-64, or even four STM-64s

    SDH uses a block frame structure to carry information, each frame consists of 9 vertical and 270×N column bytes. N column bytes, each byte contains 8bit, the entire frame structure is divided into section overhead (Section OverHead, SOH) area, STM-N net load area and management unit pointer (AU PTR) area of three regions, of which the section overhead area is mainly used for the operation of the network, management, maintenance and assignment to ensure that the information can be properly and flexibly transmitted, it is also divided into regeneration section overhead (section OverHead, SOH) area, STM-N net load area and management unit pointer (AU PTR) area. It is also divided into Regenerator Section OverHead (RSOH) and Multiplex Section OverHead (MSOH). The net load area is used to store the bits really used for information service and a small number of channel overhead bytes for channel maintenance and management; the AU PTR is used to indicate the first byte of information in the net load area is in the net load area, and the AU PTR is used to indicate the first byte of information in the net load area is in the net load area. The management unit pointer is used to indicate the exact position of the first byte of information in the net load area within the STM-N frame so that the net load can be correctly separated during reception.

  & amp;nbsp; SDH frame transmission according to the left to right, from top to bottom of the order of the string code stream transmission, each frame transmission time of 125μs, 1/125 x 1,000,000 frames per second, the number of bits per frame for the STM-1 for the 8bit × (9 × 270 × 1) = 19,440bit, then the STM-1 transmission rate is 19,440bit. -1 transmission rate is 19440 × 8000 = 155.520Mbit/s; while the STM-4 transmission rate is 4 × 155.520Mbit/s = 622.080Mbit/s; the STM-16 transmission rate is 16 × 155.520 (or 4×622.080)=2488.320Mbit/s.

    SDH transmits service signals when various service signals have to enter the SDH The mapping, positioning, and multiplexing steps are required for each frame to enter the SDH. The multiplexing mapping structure recommended by the ITU-T G.707 standard is shown in the figure.

  & amp;nbsp; Mapping is a variety of rates of the signal first after the code rate adjustment into the corresponding standard container (C), and then join the channel overhead (POH) to form a virtual container (VC) process, the frame phase deviation is called frame offset. Positioning is the frame offset information into the branch unit (TU) or management unit (AU) process, which is realized through the function of the branch unit pointer (TU PTR) or management unit pointer (AU PTR). The concept of multiplexing is relatively simple; multiplexing is the process of adapting signals from multiple lower-order channel layers into a higher-order channel layer, or adapting signals from multiple higher-order channel layers into a multiplexing layer. Multiplexing is also the process of organizing TUs into higher-order VCs or AUs into STM-N through byte-interleaved interpolation. Because the VC branch signals after processing by TUs and AU pointers have been synchronized, the multiplexing process is synchronous multiplexing similar to the principle of serial-to-parallel conversion of data.

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    OptiX 155/622H Metro1000 Packet Domain Typical Networking Approach

    The OptiX 155/622H enables packet-domain based Ethernet service networking overlay on TDM networks.

    Typical packet domain networking is shown in Figure 1.

    The access/aggregation/core layers all contain two independent domains (TDM and packet domain). In the access layer, including TDM service ring (i.e., SDH ring its maximum rate of STM-1/4) and packet data service ring (i.e., GE ring). At the aggregation/core layer, it includes the TDM service ring (i.e., SDH ring with a maximum rate of STM-16/64) and the packet data service ring (i.e., 10GE ring).

    The E1 services at the access layer are first mapped to the SDH ring at the access layer (i.e., the STM-1/4 service ring in the figure), and then aggregated to the SDH ring at the aggregation/core layer through the aggregation nodes. SDH ring (i.e., the STM-16/64 service ring in the figure).

    The FE services of the access layer are first aggregated to the packet data service ring of the access layer (i.e., the GE ring in the figure), and then aggregated to the packet data service ring of the aggregation/core layer through the aggregation nodes. ring (that is, the 10GE ring in the figure).

    Figure 1  Typical Networking Mode of Packet Domain

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