When the telephone networks started to go digital in the 1960s, the voice sampling frequency was carried in the physical layer of the multiplexed digital voice signal. This frequency was transported across the network so that all voice switches could operate at the same frequency, as any mismatch would cause clicks and pops in the voice channel.
Packet networks technologies such as Ethernet also have a physical layer signal that carries the timing of the individual bits. However, in Ethernet that’s where it stopped – it was purely a point-to-point bit clock, and was only intended to allow the bits to be accurately transferred from one device to another.
Synchronous Ethernet (SyncE) uses that physical timing signal to carry an accurate frequency as well. That way a chain of SyncE-enabled Ethernet switches can distribute a frequency from one side of a network to the other. This is more accurate than trying to carry frequency at the packet level, because it is immune to packet delay variation. SyncE is commonly used to provide frequency synchronisation in networks, and in particular to provide an accurate reference frequency to mobile base stations. It enables you to deliver synchronization services that meet the requirements of the present-day mobile network, as well as future Long Term Evolution (LTE)–based infrastructures.
Synchronization is a key requirement for circuit (emulation) services and mobile radio access technologies. Traditionally, mobile networks used SONET/SDH technologies to backhaul voice and data traffic, and the native support for frequency of SONET/SDH to synchronize their radio network. With the need for greater-capacity backhaul networks, packet-based technologies such as Carrier Ethernet (which do not support the transfer of frequency) and wireless technologies such as frequency division duplex and time-division duplex require not only frequency synchronization but also proper time and phase alignment. This requirement is fulfilled by Synchronous Ethernet, which is used for physical layer frequency synchronization of connected access devices (such as base stations, access nodes, and so on). Synchronous Ethernet supports sourcing and transfer of frequency for synchronization purposes for both wireless and wireline services and is primarily used for mobile backhaul and converged transport.
Synchronous Ethernet is used to transfer clock signals over Ethernet interfaces. The Synchronous Ethernet operation is described in three ITU recommendations:
Packet networks technologies such as Ethernet also have a physical layer signal that carries the timing of the individual bits. However, in Ethernet that’s where it stopped – it was purely a point-to-point bit clock, and was only intended to allow the bits to be accurately transferred from one device to another.
Synchronous Ethernet (SyncE) uses that physical timing signal to carry an accurate frequency as well. That way a chain of SyncE-enabled Ethernet switches can distribute a frequency from one side of a network to the other. This is more accurate than trying to carry frequency at the packet level, because it is immune to packet delay variation. SyncE is commonly used to provide frequency synchronisation in networks, and in particular to provide an accurate reference frequency to mobile base stations. It enables you to deliver synchronization services that meet the requirements of the present-day mobile network, as well as future Long Term Evolution (LTE)–based infrastructures.
Synchronization is a key requirement for circuit (emulation) services and mobile radio access technologies. Traditionally, mobile networks used SONET/SDH technologies to backhaul voice and data traffic, and the native support for frequency of SONET/SDH to synchronize their radio network. With the need for greater-capacity backhaul networks, packet-based technologies such as Carrier Ethernet (which do not support the transfer of frequency) and wireless technologies such as frequency division duplex and time-division duplex require not only frequency synchronization but also proper time and phase alignment. This requirement is fulfilled by Synchronous Ethernet, which is used for physical layer frequency synchronization of connected access devices (such as base stations, access nodes, and so on). Synchronous Ethernet supports sourcing and transfer of frequency for synchronization purposes for both wireless and wireline services and is primarily used for mobile backhaul and converged transport.
Synchronous Ethernet is used to transfer clock signals over Ethernet interfaces. The Synchronous Ethernet operation is described in three ITU recommendations:
- G.8261—Defines the architecture and wander performance of Synchronous Ethernet networks.
- G.8262—Specifies timing characteristics of synchronous Ethernet equipment clock (EEC).
- G.8264—Describes the Ethernet Synchronization Message Channel (ESMC).
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