Michel Ouellette

Synchronous ethernet: a method to transport synchronization

This article discusses the evolving transport architecture, covering some of the synchronization distribution problems to many endpoints where mobile backhaul and TDM emulation occur. It shows how synchronous Ethernet fits into both the Ethernet and synchronization architectures, and discusses how this helped development in standardization bodies. Standardization allows the key building blocks of Ethernet silicon and specific timing devices to be developed, which allows a robust system implementation to be constructed while allowing interworking with and migration from existing SONET/SDH-based transport infrastructure. Finally, results are shown that indicate a very high level of performance is achievable with Synchronous Ethernet not subject to the normal packet delay variation and traffic load conditions that can occur in packet based networks.

Using IEEE 1588 and boundary clocks for clock synchronization in telecom networks

This article describes the use of IEEE 1588 and boundary clocks for clock distribution (phase/time transfer) in telecom networks. The technology is primarily used to serve the radio interface synchronization requirements of mobile systems such as WiMAX and LTE, and to reduce the deployment and dependence of GPS systems in base stations. We discuss the most important functions that are necessary for phase/time transfer and present some initial field trial results using a chain of cascaded boundary clocks and synchronous Ethernet links across a packet and optical transport network that spans tens of kilometers and tens of network elements. The results indicate that it is possible to transfer accurate phase/time in a telecom network and meet the requirements of mobile systems. The article also discusses some of the challenges and highlights the ongoing activities in standardization bodies so that IEEE 1588 can be used as a technology in telecom networks.

Development of the first IEEE 1588 telecom profile to address mobile backhaul needs

This article describes the work performed by ITU-T SG15Q13 for defining the first telecom profile based on the use of IEEE Std 1588-2008. The first profile is specifically developed for the distribution of frequency using unicast IPv4 transmission, and required adaptation of the IEEE1588 protocol to make it suitable for the telecom environment. The objectives, reasons, and results of this adaptation are explained in this article. Since the distribution of phase/time is also gaining importance in telecom, the article briefly discusses the objectives, reasons, and upcoming work for the definition of another profile that will leverage other functions and clocks defined in IEEE1588.

Simulations of a chain of Telecom Boundary Clocks combined with Synchronous Ethernet for phase/time transfer

This paper describes the use of Boundary Clocks for clock distribution (phase/time transfer) in telecom networks. The technology is primarily used to meet synchronization requirements of mobile systems such as TD-SCDMA and LTE, and to reduce the use of and dependency on GPS systems deployed in base stations. We describe the most important functions of a Telecom Boundary Clock, which are under discussion at ITU-T. We then present a network reference model and simulation model based on IEEE1588 and Synchronous Ethernet. The results indicate that it is possible to transfer phase/time in a telecom network for meeting the microsecond-level requirement of various mobile systems. The paper also discusses some of the ongoing activities in standardization bodies so that IEEE1588 can be used as a technology in telecom networks.

Using an IEEE 802.1AS network as a distributed IEEE 1588 boundary, ordinary, or transparent clock

IEEE 802.1AS includes a very specific profile of IEEE 1588 that only runs at layer 2 over networks that follow the IEEE 802 architecture. It has some significant performance and scalability advantages, but at the cost of not allowing non-PTP-aware devices. This paper describes how a network having a common source of time can act as a distributed IEEE 1588 boundary, ordinary, or transparent clock, allowing the network to transport synchronization between portions of an IEEE 1588 network domain, and do this for any number of domains simultaneously. The network that acts as a distributed clock can be a PTP network supporting a profile that is different from that of the domains whose timing it is transporting. As one example, an IEEE 802.1AS network can act as a distributed IEEE 1588 boundary, ordinary, or transparent clock. As part of the discussion, the paper also shows that an IEEE 1588 boundary clock and peer-to-peer transparent clock are functionally equivalent in the manner in which they transport synchronization, and that the principal difference between the two is that the former invokes a best master clock algorithm (either default or alternate) and implements the full PTP state machine, while the latter does not. The concepts of distributed BC, TC, and OC, and the equivalence of the BC and peer-to-peer TC may be considered a new way of looking at the transport of synchronization in a network based on IEEE 1588.