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Network time protocol synchronisation for IPTV, IMS and femtocells

Posted: 16 Feb 2012     Print Version  Bookmark and Share

Keywords:Telecom networks  Network Time Protocol  NTP 

Most time references that need to be synchronised are those serving customer end-points. Providing NTP at all of these points calls for very high NTP server transaction capacity, bandwidth overhead, security, authentication, consistency, and network delay.

IMS applications
The IP Multimedia Sub-system (IMS) architecture has a multitude of functions that are distributed across many servers in the data centre hosting the HSS/OSS/BSS functions. Billing and logging is for example decomposed into multiple functions that interface with many other servers. So what was previously one integrated software system on a classical mobile switching centre (MSC) or public switched telephone network (PSTN) switch is now embodied in many servers with much richer and more complex processes and many potential interfaces. Time differences between logging and billing instances are widely distributed over a number of servers in a data centre and also geographically distributed over multiple data centres.

The Call Detail Record (CDR) / Internet Protocol Detail Record (IPDR) is the basis for the billing contract with subscribers, for inter-carrier reconciliation, for taxation and for revenue statements that describe average revenue per user (ARPU). The IPDR is collected from a multitude of network instances depending on the specified service layer and application with well defined interfaces acting as collection points. Best effort NTP is no longer good enough for such a rich and complex service and application environment.

Fully redundant carrier grade NTP can deliver inherently precise and accurate timestamps with extremely stable performance.

Femtocell applications
The femtocell is a consumer device that connects to the service provider's network via residential broadband to provide UMTS-WCDMA services in residential areas. Frequency accuracy requirements for femtocells are typically in the range of 250 parts per billion (ppb).

Carrier grade NTP provides the necessary capacity and redundancy to serve thousands of femtocell devices on a single server and ensure high availability.

Closer to the edge
The pressure to meet all these needs, support new services and devices, improve network performance, accelerate fault diagnosis and recovery, and streamline billing, is driving the requirement for carrier grade NTP services. Operators must move accurate time closer to the network edge to manage end-user devices.

NTP has proven its value to both enterprise and carrier operators. Telecommunications network and service transitions to packet-based technologies increases the importance of deploying a carrier grade NTP implementation.

About the author
Barry Dropping is currently the Director of Product Line Management for Symmetricom's communications solutions. In this position, Mr. Dropping directs the development of next generation synchronisation products for fixed, mobile and cable operators. Mr. Dropping joined Symmetricom in October 1999 following its acquisition of Hewlett-Packard's communications synchronisation business. Mr. Dropping spent 15 years at Hewlett-Packard where he served in a variety of management positions across engineering, marketing and operations. Mr. Dropping holds a BS in Electrical Engineering Technology from the DeVry Institute.

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