Application Notes

The emerging Worldwide Interoperability for Microwave Access (WiMAX) standard promises to be the core enabling technology for next generation broadband mobile wireless applications including last mile broadband, hotspots, cellular backhaul and full mobile high speed broadband access. Architected to ensure low latency and low jitter to support real-time services, WiMAX provides a wide range of QoS levels appropriate for a variety of applications and subscriber requirements including internet access, streaming services, interactive gaming, video-on-demand, and voice-over-IP (VoIP) services. With its basis in robust Orthogonal Frequency Division Multiplexing (OFDM) modulation, shared data rates up to 70 Mbps, and an outstanding range of 3 to 5 miles, WiMAX leverages an internet protocol (IP) core that creates an open architecture for mobile data networks while significantly reducing network cost and complexity for delivery of high bandwidth personal broadband services.

Mobile operators are racing to deploy high-speed data services in order to acquire and retain lucrative mobile professional users. Because high-speed data services require increased backhaul capacity, mobile operators are seeking alternative, lower-cost backhaul methods in order to meet increasing data demands. At the same time, cost reduction measures must not sacrifice consistent and high-quality service. As the network shifts to an Ethernet/IP backhaul, maintaining precise frequency distribution throughout the network is essential for maintaining service level assurance. The quality of synchronization mobile operators put into their network directly impacts the quality of service (QoS) that comes out of their network.

Time and frequency alignment is critical for ensuring quality of service (QoS) for applications such as voice, real-time video, wireless hand-off, and data over a converged access medium. As telecom networks evolve from Circuit to Packet switching, proper synchronization (frequency and time) is needed for IP networks to achieve performance quality comparable to that of legacy circuit-switched networks.This brief addresses the impact of proper network synchronization on services and applications, the various technologies emerging to fulfill this need and also clarifies the distinction between frequency and timing synchronization.

The basic theory behind BESTIME® technology is the use of multiple sources of time and frequency to compare the others and adjust to what is determined as known error. BESTIME adaptively ensembles commonly available frequency sources including T1 or E1 signals, GPS signals, remote oscillator signals, and a local oscillator to provide unparalleled time and frequency output performance.

Improving Oscillator Long-term Stability for Synchronization Applications Modern applications in digital telecommunications, metrology, manufacturing, calibration, wireless communications, and power transmission require highly-accurate timing. Equipment functionality and reliability and the quality of services delivered can be dramatically affected by the proper application of precise timing units. Until recently, the cost of highly-accurate timing was prohibitive. Now, excellent network and timing synchronization are available at reasonable cost.

Reduction of user churn is a key business driver for wireless network operators. Carriers focus on improvement of network performance, efficiency of customer support, and introduction of advanced service bundles to bolster customer retention rates in today's fiercely competitive marketplace. For wireless network operations and engineering staffs, this means improving network coverage and hand-off performance to reduce dropped call rates – a key contributor to user churn.

Synchronization is a mission-critical infrastructure technology for telecommunications networks. Within a telecommunications network, synchronization networks are deployed and maintained separate from the traffic-carrying switching and transmission network. This is very similar to the way signaling networks are deployed.

The Building Integration Timing Supply (BITS) concept is the basis for providing synchronization throughout today's Central Office. The BITS hardware foundation is a combination of a synchronization reference, such as a Primary Reference Source (PRS) and a BITS Master Shelf, which distributes synchronization signals to the Central Office's (CO's) network elements. Converting from legacy to Next Generation BITS is the subject of this paper.

This application note covers the basics of GPS antennas, installation and cables. The paper starts with the basics of why antennas are necessary and moves into the practical areas of installation and how to be the most successful in receiving satellite signals.

This application note highlights the software availability various operating systems within Symmetricom's PCI Family Drivers and bc635/637VME Drivers.

The North American Electric Reliability Council (NERC) has conducted a comprehensive investigation of the August 14, 2003 blackout. The results of NERC’s investigation contributed significantly to the U.S./Canada Power System Outage Task Force’s November 19, 2003 Interim Report identifying the root causes of the outage and the sequence of events leading to and during the cascading failure.

This application note discusses time scales of measurement, digital clock accuracy and synchronization, IRIG Time Code Formats, Other Time Code Formats and IEEE 1344 Compliance.

WiMAX (802.16e) will be the 1st truly global mobile broadband standard 4G wireless technology. Mobile WiMAX requires synchronization & holdover technology and GPS with holdover is the recommended source for synchronization for WiMAX base stations today. This presentation discusses how Symmetricom’s TimeMAX offers a high value, simple packaged sub-system solution for mobile WiMAX.

Telecommunications networks are rapidly shifting from circuit switched to packet switched technologies to meet exploding demand for bandwidth in both core and access networks. Traditional circuit switched TDM networks were engineered to carry precise frequency synchronization throughout the network. Access platforms such as wireless base stations and MSANs (multi service access nodes) rely on synchronization delivered over the network backhaul connection to assure high QoS for end user applications. A key dependency in the evolution to Ethernet backhaul in telecom networks is the ability to deliver carrier grade synchronization over Ethernet to remote wireless base stations and access platforms.

Never before have telcos, cable operators, equipment makers, and content providers had so many ways to engage the consumer – creating a cacophony of complex provider, service, content, and device scenarios. Operators find themselves caught in a convergence of multiple new-media technology plays. Consumers meanwhile struggle to make brand choices as they switch from "watching what's on," i.e., linear consumption models, to more on-demand models like IPTV, online social networking, games, and downloads. Telcos, however, have historically enjoyed a unique advantage versus the other players: superb quality assurance. For decades people have expected to hear a dial tone when they pick up the phone. Clearly, a winning strategy will be to bring that same level of customer confidence to other arenas as well. That means bringing the same quality assurance strengths into play. One of those is the ability to synchronize the network elements that must interoperate smoothly to enable end-to-end sessions. But rather than just phone calls, today's sessions might also be games, on-demand movies, podcasts, and other interesting interactive applications.

No longer confined to the data center, Network Time Protocol is an emerging force in the delivery of new digital services and the reliable operation of telecom networks.In the last few years, telecom networks have undergone a substantial change – both in terms of technology as well as in the services they support. In particular, packet-based technologies have placed new demands on network-wide timing. This paper will discuss how these changes are creating new requirements in the accuracy, security, and availability of NTP-based time. Network operators will have to adjust.

The foundation of the Next Generation Network (NGN) is a packet-based transport. The network transition from traditional circuit switched or Time Division Multiplex (TDM) networks to packet technologies started many years ago and gradually the deployment of packet equipment is migrating to the access networks. It is expected that some parts of the network will continue to use TDM elements for the next 5 to 10 years until they reaching end-of-life. Thus, the network today is hybrid with a mix of circuit and packet technologies, particularly in the access and metro layers.This overview brief demonstrates how during this period of transition and evolution consistent and reliable timing will be essential for quality assurance, network performance, service availability and seamless interoperability across the diverse universe of network elements, service infrastructure and customer premise equipment.

Symmetricom's TimeSource® 3500 and TimeSource 3600 standard wall antenna kits do not include lightning protectors. When the antenna is installed on the side of the building, the antenna is in the zone of protection and is protected from lighting strikes as described in the Standard for the Installation of Lightning Protection Systems (NFPA 780), 2000 Edition.

NTP is a well know, well proven IP technology that currently provides time services with accuracy anywhere from a millisecond to a few seconds. It has traditionally been deployed in the IT data center where it is used to provide timestamps to computers, network elements, PCs, and servers.  Accuracy of one second has normally been considered adequate for these applications. The distribution of time on a network is the domain of NTP. This application brief focuses on the delivery of time for billing and logging services based on servers deployed in the IP NGN..

To implement the robust, deterministic NTP service that is more appropriate for the stringent requirements of real-time services, major service providers are now deploying Symmetricom next generation carrier class NTP blades into their existing SSU and BITS platforms. This case study outlines the compelling reasons why this is a preferred option for NTP on the NGN.

This case study demonstrates how TELUS and Symmetricom are partners in the process of evolving the TELUS telecom infrastructure to support new service offerings that are enabled by broadband technologies. The study shows how the Symmetricom synchronization platforms that support the integration of time transfer technologies such as NTP (Network Time Protocol) provide TELUS the capability of addressing both network frequency synchronization requirements and existing and emerging requirements for time of day distribution for both applications and services. The study makes that case that the TELUS decision to upgrade the synchronization component of the network is driven by both business and technical aspects of providing the TELUS customer base with an outstanding QoE (Quality of Experience) that is tied to a network that delivers high levels of reliability and performance. The replacement of the older synchronization technologies, due to age, coupled with the value add capabilities of the integrated timing component in the new synchronization platforms makes for an attractive business case that executive level managers can use to justify budgets and investment.

Synchronization of time and frequency has always been crucial to cable networks since the development of data over cable service interface specification (DOCSIS®), the first and still current cable-modem interface standard. Synchronization remains essential to cable networks for two reasons: first, because the physical-transmission medium, in this case coaxial cable, is shared by all cable modems on the network, basic connectivity is likely to cause high levels of transmission interference unless synchronization is precise. In fact, existing DOCSIS systems maintain five-nanosecond time-and frequency accuracy within a given cable modem termination system (CMTS). Second, various new specifications for flexible CMTS architectures and new services like T1 or E1 circuit emulation require good synchronization in cable networks.

As more mobile network operators deploy high-speed data services using IP backhaul, the need for stable and accurate frequency reference becomes more critical. This need is particularly apparent for applications such as successful hand-offs between base stations and the transport of real-time services.

Historically, synchronization and timing has been widely accepted as a fundamental component in telecommunication networks for the reliable and seamless transmission of voice, video and data. Today, precise synchronization is a rising consideration for 3G mobile operators in order to achieve network performance that will parallel wireline services.

The task of delivering a centralized reference signal to a number of different equipment stations without degrading the signal or creating crosstalk can be difficult, particularly when up to 100 locations require this signal. This situation is encountered in many engineering and calibration laboratories and production test facilities. The model 6502 distribution amplifier provides a means to divide and deliver a 100 kHz to 10 MHz sine wave signal to 10 locations with high channel-to-channel isolation and low added phase noise.

Deploying Synchronous Ethernet allows an upgrade to next generation networks while driving cost out of such implementations. Sync E is a simple link-by-link replacement for SONET/SDH that retains backward compatibility, leverages the existing synchronization architecture and cost effectively enables current and next generation services such as IP-based video services.

The rapid explosion of over-the-top video services and increasing competition is driving dramatic growth in internet demand for downstream bandwidth.  Today's cable broadband networks have large downstream offerings leaving many upstream ports unused.  This application brief addresses how upgrading to M-CMTS provides a low cost alternative to deliver increased downstream capacity and harvest stranded upstream ports.