Synchronization over Ethernet and IP in next-generation networks

Since the 1970s and ’80s, most telecommunications operators have set up synchronization networks to synchronize their switching and transmission equipment. It has been recognized that the importance of network synchronization goes even further than SDH and legacy telephone networks: asynchronous transfer mode (ATM) and cellular mobile telephone networks (Global System for Mobility [GSM], Global Packet Radio Services [GPRS], Universal Mobile Telecommunications Services [UMTS]) are two striking examples where the availability of network synchronization references has been proven to significantly affect the quality of service. The recent migration of network operators to the packet- switched next-generation network (NGN) once again poses newer and even more difficult problems for network synchronization. This widens the scope of interest in synchronization beyond specialists, reaching the wider audience of telecommunications engineers in general. An example is the distribution of synchronization to next-generation wireless base stations, which are connected to the core network only via packet-switched networks, but still require highly accurate synchronization to meet standard quality of service expectations.