A Novel Local Timestamp Based Adaptive Clock Method FOR TDM over Ethernet

Clock methods for TDM over Ethernet network are introduced. A new adaptive clock method is presented. The method is a kind of timestamp based adaptive method, but no timestamp needs transporting over Ethernet network. By using the local oscillator and a counter, the timestamp information (local timestamp) related to the service clocks of the two PEs (provide edge) can be attained. By statistic computing, the timestamp information can be converted into a random data sequence that accords with the Karlman filter equations. By using Karlman filter algorithm, the noise caused by Ethernet network can be filtered and the useful timestamp can be extracted out. With the timestamp and a voltage-controlled oscillator, clock frequency of local PE can be adjusted the same as clock frequency of the remote PE. Experimental results verify that the proposed method is better than the present congener methods.