| US 7,382,723 B2 | ||
| Hitless switching system and transmission apparatus | ||
| Atsushi Sutoh, Tokyo (Japan); and Kazuhiro Oda, Tokyo (Japan) | ||
| Assigned to Nippon Telegraph and Telephone Corporation, Tokyo (Japan) | ||
| Filed on Mar. 03, 2003, as Appl. No. 10/376,262. | ||
| Claims priority of application No. 2002-056320 (JP), filed on Mar. 01, 2002. | ||
| Prior Publication US 2003/0165115 A1, Sep. 04, 2003 | ||
| Int. Cl. H04J 1/16 (2006.01) | ||
| U.S. Cl. 370—227 [370/535] | 10 Claims |
| 1. A hitless switching system for switching between signals transmitted over a plurality of transmission lines, said hitless
switching system comprising a sending apparatus and a receiving apparatus,
said sending apparatus comprising:
a distributing part for dividing an original signal into a plurality of signals; and
a transmitting part for transmitting the divided signals over one or a plurality of transmission lines with redundancy,
said receiving apparatus comprising:
a phase difference detection part for detecting phase difference between the divided signals sent from said sending apparatus;
a phase difference absorbing part for absorbing said phase difference detected by said phase difference detection part;
selectors each of which selects one signal from the divided signals in which said phase difference is absorbed by said phase
difference absorbing part; and
a restoring part for restoring the original signal from signals output from said selectors,
said distributing part comprising:
a part for dividing said original signal into virtual concatenation signals as the divided signals by using virtual concatenation
technology; and
a part for inserting H4 byte multi-frame into each virtual concatenation signal,
wherein said phase difference detection part detects said phase difference by using the H4 byte multi-frame, and said phase
difference absorbing part absorbs said phase difference by using elastic store memories.
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