Press information
Hanover, 17. August 2012
arcutronix supports the quality rating of LTE infrastructure
Access specialist arcutronix includes in its demarcation devices for Precision-Time-Protocol (PTP; IEEE 1588) comprehensive rating functionalities about excellence and quality of the synchronisation. Using this, individual predications about nature and usage of the used Ethernet are possible, without any need to install additional measurement equipment.
The 4th generation mobile technique LTE ( Long Term Evolution) is demanding much higher requirements on clocking and synchronisation as with former technologies. Even more, the back-hauling of the antennas for LTE (eNodeB) is purely based on Ethernet, which did not offer special features for clock and synchrony up to now. Ethernet is normally an asynchronous and packet-oriented transmission technology mainly used in LAN. Due to that there was no need to fulfil any demands on these quality features and in regular products nothing was prepared to support them.
Knowing these new demands of back-hauling antennas via Ethernet, arcutronix implements in its access devices synchronous Ethernet (Sync-E) and PTP. Therefore arcutronix offers best conditions and equipments to back-haul LTE.
Sync-E works on physical layer similar to SDH. The Precision-Time Protocol, defined by IEEE recommendation 1588v2-2008, is a packet-based method to synchronise clocks and is independent to the physical transport, which is a big difference to Sync-E. Using Master-Slave architecture, the timing source (Grandmaster) sends periodically packets, which are carrying the actual time/clock. In a multi-stage procedure, each attached slave determines the packet-delay between itself and the Grandmaster. Knowing this individual packet-delay the slave can adjust its clock correctly. The algorithm used to calculate the delay of the timing-packets requires precise timestamps for the sending and receiving time. Depending on the quality of the timestamps, the slave’s established clock can be the same as on the Grandmaster, varying only a few Nano-seconds.
As for all packet-oriented procedures, there are variations in the packet-delay for PTP packets and so the value is not constant, but slightly fluctuating. The smaller the packet-delay variation, the better is the result for the calculated clock at the PTP slave. In addition, any change in the topology of the network, caused by failure of lines or nodes, will lead to massive change in the mean-packet-delay between Grandmaster and slave.
The calculation of the packet-delay between slave and Grandmaster plus the optimisation of the network to small packet-delay variations is one of the big challenges for operators and providers. The used network models are never matching to existing lines. They can only be seen as a generalisation of common known networks.
arcutronix offers in its products the option to log the calculated packet-delays and to store this over a long period of time (up to 3 years). Using these loggings, conclusions about the network can be done and ways for corrections can be found. Any changes in the topology can be back-tracked and the influence on the quality-level of the PTP. So this new feature is not only a mighty tool for operators but also very well suited in test cases and to improve further models of existing topologies.