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LIU delivers redundancy w/o relays

Posted: 22 Sep 2005 ?? ?Print Version ?Bookmark and Share

Keywords:t1? e1? exar?

With tremendous demand in the T1/E1 area, Exar has developed what it claims is the first integrated 28-channel T1/E1 (line interface units) LIU/framer with VT/TU Mapper/DeMapper and the M13 multiplexer for optical transport applications.

Designed to process the section line and path overhead in the SONET/SDH datastream, Voyager, part number XRT86SH328, is a highly integrated device that helps reduce board space in a big way.

But that's not all. Each LIU channel on the XRT86SH328 supports the company's R? technology (reconfigurable, relayless, redundancy). With conventional methods, many relays are needed to provide redundancy in tributary aggregation applications such as multi-service provisioning platforms, optical transport systems, routers and wireless transport systems.

"Relays are not reliable," said Raman Subramanian, director of strategic marketing, Networking and Transmission products. "If you're depending on a relay, the redundancy won't be that good." And for companies like Alcatel and AT&T that need to guarantee 99.9 percent reliability, redundancy is pertinent when their systems fail. To avoid losing data, redundancy allows data to be transferred to an alternate system.

Exar also made Voyager reconfigurable. Since T1 lines are used in the United States, and E1 in Asia and Europe, manufacturers have had to build two different systems.

"They have to have inventory of two products because they have to change components on the board. What we did in our device is [give the designer] the ability to reconfigure the software o they can build one system and they can reconfigure the system to E1 without changing any components on the board," Subramanian said.

Voyager?s high-function integration and relayless features make it an attractive choice for customers designing T1/E1/J1 interface cards.

"The reason we are the industry's first is there is nobody today in the marketplace that offers the line interface unit combined with the other access controllers, such as framers, mappers, and multiplexers," Subramanian said.

"The competition in the market supplies two or three separate solutions," which results in higher cost, debugging time, and power consumption, he said.

The mixed-signal IC provider uses standard CMOS technology to manufacture Voyager. To achieve greater function integration and lower power consumption, the company switched to 1.8?m technology from 3.5?m.

"If I take the power consumption for [existing solutions] and compare it with our offering, it is a 20 to 25 percent power savings," he said.

The XRT86SH328 operates at 3.3V/1.8V with 3.3-V tolerant I/Os over the industrial temperature range.

It integrates 28-channel T1/E1 LIUs, DS1/E1 framers, as well as SONET and DS/3 framers. It also integrates a desynchronizer with an internal pointer leak algorithm, which removes the jitter due to mapping and pointer adjustments from the T1 and E1 signals that are demapped from the incoming SONET/SDH datastream.

The desynchronizer circuits do not need any external clock references for its operation. An integrated clock synthesizer eliminates the need for external PLL, and offers one bill of materials. The chip also provide DS3 capabilities, including M13 functionality, by multiplexing 28/21 T1/E1?s onto a DS3 signal for sending either on serial DS3 interface or by mapping onto an STS-1. The DS1s or E1s received from a DS3 signal can be mapped into SONET/SDH through VT/TU mapping.

When three Voyager chips are combined on one line card, they create a complete OC-3/STM- solution that supports up to 84 T1 or 63 E1 port aggregation applications. The XRT86SH328 has all of the SONET/SDH framing functions to provide an OC-3/STM-1 compliant interface.

Samples of the XRT86SH328 are available in 30 days. In 1,000-piece quantities, the device costs $151 each. It is available in a PBGA package.

- Ismini Scouras

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