TAILIEUCHUNG - Switching Theory: Architecture and Performance in Broadband ATM Networks phần 2

Các số liệu thống kê quyết định ở đầu ra của máy dò có thể được đại diện bởi một nT phức tạp cột vector, được đưa ra bởi y là ma trận tương quan không gian-thời gian và ny là vector nhiễu kết quả. sơ đồ khối của người nhận không gian-thời gian bộ lọc phù hợp | 30 Broadband Integrated Services Digital Network Figure . Example of positive justification with AU-4 V3 V4 are added as shown in Figure . V1 V2 and V3 represent the pointers TU-11 PTR TU-12 PTR TU-2 PTR in their respective multiframe whereas V4 is left for future usage. Bytes are numbered 0 through 103 TU-11 0 through 139 TU-12 0 through 427 TU-2 with byte 0 conventionally allocated to the byte following V2. So V1 and V2 carry the offset to indicate the current starting byte of the multiframe whereas V3 and the byte following V3 are used for negative and positive justification. Since also the multiframe needs to be synchronized to properly extract the pointer bytes all TUs are multiplexed so have to same phase in the multiframe and the phase alignment information is carried by byte H4 of POH in the higher-orderVC carrying the TUs. Using the pointer information allows a VC to float within its TU which is called the floating mode of multiplexing. There are some cases where this floating is not needed namely when a lower-order VC-i i 11 12 2 is mapped onto the a higher-order VC-j j 3 4 the two VC signals being synchronous. In this situation called locked mode VC-i will keep always the same position within its TU-i thus making useless the pointer TU-i PTR. Therefore the 500 multiframe is not required and the basic 125 frame is used for these signals. Synchronous Digital Transmission 31 . Mapping of SDH elements How the mappings between multiplexing elements are accomplished is now described . Figure shows how a TUG-2 signal is built starting from the elements VC-11 VC-12 andVC-2. These virtual containers are obtained by adding a POH byte to their respective container C-11 C-12 and C-2 with capacity 25 34 and 106 bytes all these capacities are referred to a 125 ps period . By adding a pointer byte V to each of these VCs recall that these VCs are structured as 500 ps multiframe signals the corresponding TUs are obtained with capacities 27

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