Agilent's Test Tool for Precision Time Protocol Enables Wireless Backhaul Synchronization

Operators are migrating to Ethernet because it is far less expensive than traditional transport technologies. N2X verified the interoperability of various vendors' Ethernet devices under extreme loads during the ISPCS Plug-fest using a novel test methodology.

Ethernet has no clock-transfer mechanism, which, for example, wireless networks need to successfully hand over calls when subscribers roam. PTP was standardized to provide this mechanism. However, the relation between a network's Master Clock, which synchronizes the Slave Clocks within the base stations, is mediated by switches and routers that introduce delays in transport. NEMs have addressed this issue by developing switches and routers with new functionality - Transparent Clocks - that modify PTP messages to correct for forwarding delays and ensure clock synchronization. Since accurate timing transfer is essential for wireless backhaul, carriers can now take advantage of cost-effective Ethernet technology using Transparent Clocks.

Agilent test results show that Transparent Clocks do not always correct accurately. Agilent's new test solution measures the Correction Factor Error, which enables NEMs to develop more accurate clocking devices and network operators to evaluate the effectiveness of those devices. This is a significant advantage because the errors can be in the order of microseconds. In addition, N2X can surround a system with many virtual Masters and thousands of virtual Slaves. This Slave-Clock Scalability enables users to emulate extreme and realistic network conditions. Leading NEMs and early-adopter network operators are already using a prototype of Agilent's tool to test their devices.

Before wireless carriers move from traditional backhaul technologies to lower-cost Ethernet, they must ensure that calls won't be dropped, which requires accurate synchronization of base stations, said Toni Piwonka-Corle, general manager of Agilent's Data Networks Operation. It is vital that the Transparent Clocks implemented in switches and routers throughout the network accurately correct for forwarding delays. Agilent's new test solution, which accurately measures the Correction Factor Error, signals the maturity of the standards and will accelerate the deployment of 1588v2 devices.

Agilent's solution also tests the performance of Boundary Clocks, which mediate the relation between a single Master and multiple Slaves in large networks. A Boundary Clock acts as a Slave to one Master and as Master to many Slaves.

The N5568A IEEE1588v2 Precision Timing Protocol Emulation software is available now. It complements the N5566A Synchronous Ethernet ESMC Emulation and G.8261 QuickTool to enhance Agilent's comprehensive Timing-over-Packet test solution.

The International Symposium on Precision Clock Synchronization for Measurement, Control and Communication (ISPCS) is the world's premier timing and synchronization event. Participants include Agilent Technologies, Alcatel-Lucent, BECKHOFF Automation, Brilliant Telecom, Calnex Solutions, Cortina Systems, Freescale Semiconductor, Hirschmann Automation and Control, Huawei, Imsys Technologies, IXXAT Automation, Meinberg Funkuhren, National Instruments, OnTime Networks, Oregano Systems, Rockwell Automation, RuggedCom, Semtech Corporation, Spectracom, Symmetricom, Tellabs, Time and Frequency Solutions, Wintegra, Zarlink Semiconductor, and Zurich University of Applied Sciences.