Cell disassembly unit, cell assembly unit, and clock reproduction method

A cell assembly unit for multiplexing a source signal having a clock which is asynchronous to a network used for transmission into fixed length cells and for sending the fixed length cells to the network, the unit comprising:

• a timing information generation circuit for generating transmission timing information which is obtained by converting transmission timing in each constant period of the clock of the source signal by the use of transmission timing of a synchronization clock of the network;
• a timing information replacement circuit for averaging differentials between adjacent pieces of transmission timing information sent from the timing information generation circuit every predetermined period and for replacing the transmission timing information on the basis of an average differential;
• and
• a cell multiplexing circuit for multiplexing the source signal and the transmission timing information replaced into the cells.

A clock reproduction method for receiving fixed length cells into which a source signal is multiplexed via a network and for reproducing a clock of the source signal which is asynchronous to the network, wherein:

• a timing information separation circuit separates transmission timing information which is obtained by converting transmission timing in each constant period of the clock of the source signal by the use of transmission timing of a synchronization clock of the network from the fixed length cells received;
• a timing information replacement circuit averages differentials between adjacent pieces of transmission timing information sent from the timing information separation circuit every predetermined period and replaces the transmission timing information on the basis of an average differential;
• and
• a clock generation circuit generates the clock of the source signal on the basis of the replaced transmission timing information.