Patent ID: 6795437
Filing Date: 2004-09-21
Classification: H04L,H04Q,H04W

Abstract:
A communications system, comprisingan access network having an asynchronous transfer mode-type transport network layer, an ATM adaptation layer, and an access network-specific user-plane transmission protocol layer on top of the ATM adaptation layer, a switching center connected to the access network by means of an interface having a time division multiplexed-type transport network layer, an interworking function provided between the access network and the switching center, wherein the switching center being configured to support said access network-specific user-plane protocol and/or a protocol of said ATM adaptation layer on said interface, the interworking function being configured to extend the ATM adaptation layer protocol and/or said user-plane transmission protocol to span between the access network and the switching center over said interface having the TDM-type transport layer. said interworking function and said switching center are configured to perform initial frame synchronization with protocol data units of said ATM adaptation layer and/or the user-plane transmission protocol layer received over said interface by searching for at least one control field having a constant value in a header of the received protocol data unit, and said interworking function and said switching center are configured to ensure the frame synchronization by counting a checksum over the header and/or payload of said received protocol data unit and comparing the counted checksum with a respective checksum received in said respective protocol data unit.