Product category:
Communications ICs (Wired)
News Release from: Zarlink Semiconductor | Subject: ZL30301 and ZL30302
Edited by the Electronicstalk Editorial
Team on 19 September 2005
Timing-over-packet devices boost QoS
A new generation of timing-over-packet devices is specifically designed to transmit timing and synchronisation over asynchronous packet switched networks.
Zarlink Semiconductor has introduced its new generation of ToP (timing-over-packet) devices specifically designed to transmit timing and synchronisation over asynchronous packet switched networks Deploying Zarlink's revolutionary ZL30301 and ZL30302 ToP devices, network operators can ensure a high quality of service (QoS) for time-sensitive applications while benefiting from the cost reductions offered by a packet switched network
This article was originally published on Electronicstalk on 7 Feb 2001 at 8.00am (UK)
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Wireless service providers can save millions of dollars in operating costs by moving to a packet backhaul infrastructure.
Zarlink's ToP technology is a corner stone of this migration process.
Traditionally, wireless network synchronisation between basestation controllers and basestations relied on a T1/E1 synchronisation and a standard PLL (phase-locked loop).
As wireless operators move to a packet backhaul approach, synchronisation will be achieved using alternative mechanisms.
One method has been to deploy GPS (global positioning system) receivers and oscillators to synchronise network traffic.
However, this approach adds significant capital and operating expense costs.
By employing Zarlink ToP technology, wireless operators can eliminate T1/E1 interfaces while at the same time achieving better than the G.823/G.824 standard for MTIE (maximum time interval error) and frequency accuracy.
ToP technology is built on a field-proven processing engine developed for Zarlink's CESoP (circuit emulation services over packet) family of devices and its leading expertise in clock recovery for circuit emulation applications.
The ToP technology encodes a PRS (primary reference source) clock at the "master" node and subsequently transmits this clock over the packet network within a specific packet connection.
The "client" node then recovers the clock through the use of complex algorithms employing a number of field-proven techniques.
For wireless infrastructure applications, the ZL30302 chip acts as the master and distributes the PRS from the RNC (radio network controller) to the Node B over an Ethernet network.
At the Node B, the ZL30301 device acts as the client, extracting timing from the packet network and creating an output clock traceable to the PRS.
Redundancy is also achieved, with the ZL30301 chip recovering up to four separate PRS clocks and selecting one for use within the client node.
Both ToP devices support differential clock recovery, a mechanism used when the same PRS is available at both the master and client nodes, for example through a Sonet infrastructure.
The devices also support adaptive clock recovery, which is commonly used at the edge of the network where a PRS is usually available only at the master node.
Equipment manufacturers and carriers have tested Zarlink's ToP technology over a variety of networks to ensure dependable performance in the presence of PDV (packet delay variation), routing changes, network overload and even network outages.
The ZL30301 and ZL30302 devices maintain an average frequency accuracy of less than +/-15ppb with a Stratum 3 quality TCXO.
Manufacturers are also using the PDH G.823 and G.824 traffic and synchronisation interface standards as guidelines for packet network timing performance.
In the event of network failure or severe network congestion, the devices will put recovered clocks into holdover until the flow of timing packets is restored.
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