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The initial VDSL2 gateways combined a gateway processor with a separate data-pump chip, complicating the system design and increasing cost. In 2008, however, we see several vendors delivering single-chip VDSL2 gateway processors, reducing cost to near that of ADSL2 gateways. In addition to smoothing the deployment of VDSL2, these new chips will encourage carriers to deploy universal gateways to all of their DSL customers. VDSL2 Processor Vendors Ikanos was an early innovator in VsDSL and already has an integrated VDSL2 gateway processor in production. The Vx180 is based on the Fusiv processor architecture that Ikanos acquired from Analog Devices in 2006. Another popular product is Infineon’s Vinax VDSL2 gateway processor. Infineon also offers the UR8 processor, which it acquired late last year along with the rest of Texas Instruments’ DSL business. Both the UR8 and Vinax are in production. Other vendors are sampling integrated VDSL2 gateway processors, including Broadcom, Centillium (Arion IIa), Conexant (CX96400), and PMC-Sierra (MSP7140). Centillium and Conexant are combining their existing VDSL2 and gateway processors into single-chip devices, whereas PMC-Sierra is combining its existing gateway processor with licensed VDSL2 technology from Aware. The Aware VDSL2 technology is also used in the Vinax products and is therefore field-tested. On the VDSL2 side, most of these products support all band plans and frequencies up to 30MHz. The PMC and Conexant products support up to 17MHz, making them poor choices for to fiber-to-the-curb (FTTC) or fiber-to-the-basement (FTTB) deployments. The UR8 supports only 8MHz VDSL2 and is best suited to central-office deployments. All provide backward compatibility with all flavors of ADSL and ADSL2. Comparing VDSL2 Processors All of these products combine a high-speed RISC CPU with integrated data-plane engines that can handle data streams at 100Mbps, the maximum VDSL2 speed. All have encryption and voice engines to offload these tasks from the main CPU. For OEMs that wish to add features in software, the Fusiv processor offers the most available CPU cycles. Cost is a key factor in these gateways. These processors all include basic system features such as memory controllers, PCI (to connect to a Wi-Fi chip), and USB. Although most offer one or two Ethernet ports, Broadcom’s chip integrates a four-port Ethernet switch, absorbing what is otherwise an external component. Broadcom also reduces system cost by integrating the VDSL2 analog front end (AFE), although it still requires an external line driver (LD). Infineon and PMC instead offer single-chip AFE/LD products, reducing chip count. Centillium’s Arion IIa is stuck in a 180nm process, increasing its manufacturing cost as well as its power dissipation. These days, software is a critical part of any processor solution. These vendors all provide low-level firmware and drivers for their processors. Only Ikanos provides a complete residential-gateway software stack. Other processor vendors have partnered with Jungo or other third parties to develop a complete software solution, but these solutions require additional licensing fees. The Shift to VDSL2 With single-chip VDSL2 gateway processors now available, building a low-cost VDSL2 gateway is now just as easy as building a low-cost ADSL2 gateway, and requires mostly the same components. Of course, the VDSL2 processor itself remains more expensive than an ADSL2 processor, due to both the more complex VDSL2 data pump and the packet processing needed to operate at 100Mbps. At list price, the premium for VDSL2 processors is about US$5, less in high volume. This premium will continue to drop over the next few years, particularly as volume builds for VDSL2. These lower prices will allow carriers to deploy VDSL2 more quickly. Even those carriers that aren’t immediately deploying VDSL2 may begin to provide universal gateways to their subscribers. Universal gateways include VDSL2 processors but take advantage of these chips’ backward compatibility to support ADSL2 as well. Thus, these gateways can be used with existing ADSL2 connections but can switch over to VDSL2 mode as soon as the central office is upgraded (and as soon as the subscriber agrees to a higher monthly fee). Carriers are wiling to pay a few extra dollars per gateway to avoid the cost of sending out a whole new gateway later. This trend will help drive shipments of VDSL2 processors.
Originally published in Nikkei Electronics Asia, January 2008
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