Transceiver puts VDSL on existing telco spectrum

Zarlink Semiconductor has produced silicon samples of the industry's first DMT-based data transceiver to fully meet international standards for four-band 12MHz VDSL.

Zarlink Semiconductor has produced silicon samples of the industry's first DMT-based data transceiver to fully meet international standards for four-band, 12MHz VDSL.

Using Zarlink's DMT transceiver, equipment companies can boost the efficiency of VDSL modems.

VDSL is an emerging standard for the symmetrical (same speed in both directions) transmission of high bandwidth services at up to 52Mbit/s over short distances using standard copper telephone lines.

However, in real-world conditions, noise and other line interference degrades signal integrity, reducing the speed and distance of VDSL transmissions.

DMT modulation technology from Zarlink helps to overcome interference by dynamically configuring the transmitted signal to match the line conditions, resulting in higher quality, error-free communications at higher datarates, over longer distances.

"The industry recognises that VDSL modems designed with DMT transceivers will deliver significantly improved speed and distance performance compared to modems using today's transitional technology", said Andrew Faulkner, VDSL product manager, Zarlink Semiconductor.

"To meet this need, we're developing a flexible, interoperable single-chip DMT data transceiver that will ease the design of full-rate, VDSL-compliant modems for customer premises and central office applications".

To implement the VDSL standard and improve system performance, Zarlink has developed advanced algorithms and several proprietary features, such as RF interference cancellation and PAR (peak-to-average ratio) reduction.

The result is a highly flexible DMT transceiver that meets the latest standards for VDSL over the full four-band 12MHz spectrum, from the ITU, ANSI and ETSI.

Zarlink's transceiver chip fully supports either the two-, three- or four-band approaches specified in the standards, and facilitates interoperability.

Robust data transfer is ensured using FEC (forward error correction) techniques, including Reed Solomon with interleaving.

Zarlink's DMT transceiver can be configured to meet all specified band plans (997, 998 and FX plan).

With DMT technology, VDSL services can easily coexist with other services in the binder group, including ADSL, ISDN and POTS (plain old telephone service).

Modems equipped with the transceiver can be configured to either protect or use spectrum usually allocated to ISDN or ADSL.

For example, configuring the optional ISDN band (25 to 138kHz) as an upstream transmission band provides a boost of 1.5Mbit/s.

This improves symmetrical operation by supplementing the heavily attenuated, higher frequency upstream band.

Zarlink's transceiver provides all the physical layer hardware to implement the VDSL standard.

The transceiver chip connects to standard ATM devices at the data link layer using a Utopia level-2 interface, and to standard Ethernet devices using an MII (media independent interface).

Zarlink is now sampling its DMT transceiver to selected alpha customers.

Advanced documentation is available under non-disclosure, including reference designs for both single and multiport designs.

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