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Conexant Next-Generation Cable Modem Supports CableHome and PacketCable Initiatives

Includes a Seamless Interface to Wireless LAN, HomePlug, and HomePNA Devices

The manufacturer says . . .

ChipCenter's Paul O'Shea says . . .

Conexant Systems, a provider in semiconductor system solutions for communications applications, today announced a single-chip cable modem that includes technology specified in CableLabs(R) DOCSIS 2.0, the latest version of the cable modem standard. Conexant's new CX24951 device is backward and pin-compatible with the company's earlier CX24943 DOCSIS 1.1/1.0 solution. In addition, it builds on the proven dual-processor architecture of the company's earlier solutions to provide the highest-performance and lowest-power consumption of any cable modem on the market today. "We are proud to be one of the first to support this exciting next-generation cable modem specification for improved data, voice, and video services while providing MSOs with the ability to offer their subscribers more efficient and value-added services," said Al Servati, director of Conexant's Broadband Communications Segment's cable modem business. "The CX24951 offers enhanced software programmability and performance along with extensive hardware and software support, allowing cable operators to expand subscribers and pursue new markets. With the introduction of our CX24951, we continue to show our commitment to providing the industry with innovative products." Conexant's CX24951 supports the new upstream physical-layer modulation technologies, advanced time division multiple access (A-TDMA) and synchronous code division multiple access (S-CDMA) as specified in the DOCSIS 2.0 standard. The CX24951 has been enhanced to offer 500 millions of instructions per second (MIPS) of processing power that allows it to be used to support the CableLabs-led CableHome initiative, without the cost or complexity of adding an external network processor for firewall, virtual private networking (VPN) and routing operations. The CableHome project extends high-quality, cable-based services to network devices within the home, and addresses issues such as device interoperability, quality of service and network management. The solution also supports the CableLabs-led PacketCable initiative. PacketCable uses Internet protocol (IP) technology to enable IP telephony, multimedia conference, interactive gaming and other multimedia applications and services. The CX24951 cable modem chip features the industry's widest variety of interconnect options. It includes an embedded interface that provides direct access to Conexant's HomePlug 1.0-certified powerline and HomePNA phoneline semiconductor solutions and other home-networking devices. An embedded universal serial bus (USB) transceiver ensures plug-and-play installations. In addition, the device's host interface supports the Personal Computer Memory Card International Association (PCMCIA) standard and can accommodate IP telephony products and IEEE 802.11a/b wireless networking transceivers. The programmability of the design also gives customers the flexibility to accommodate application-specific requirements, worldwide standards and unique value-added features. The CX24951 joins Conexant's family of Internet access solutions built upon a strong heritage of industry-standard products. This next-generation cable modem is supported by a reference design that includes both hardware and software, and speeds time-to-market for complete DOCSIS/EuroDOCSIS 2.0/1.1/1.0-capable cable modem solutions used in Ethernet/USB or peripheral component interconnect (PCI) applications. The reference design also features Conexant's advanced CN2811 radio frequency silicon tuner and includes the full range of DOCSIS/EuroDOCSIS 2.0/1.1/1.0-capable software. Conexant has one of the industry's most comprehensive portfolios of products and technologies for broadband digital information and entertainment networks, including dial-up and broadband modems, home network processors, set-top box systems and components, and a comprehensive suite of video and multimedia semiconductors and system solutions. About Conexant Conexant Systems, Inc., a worldwide leader in semiconductor system solutions for communications applications, leverages its expertise in mixed-signal processing to deliver integrated systems and semiconductor products through two separate businesses. The Broadband Communications business develops and delivers integrated solutions that enable digital entertainment and information networks for the home and small office. Mindspeed Technologies, the company's Internet infrastructure business, designs, develops and sells a complete portfolio of semiconductor networking solutions that facilitate the aggregation, transmission and switching of data, video and voice from the edge of the Internet to linked metropolitan area networks. Conexant Systems Web Site

Conexant comes from the heritage of Rockwell, as such they have a large chunk of the modem market. And they are moving in that direction for DSL and cable modem markets as well. They know modems and have always been in the modem business, from narrow band to broadband. Their newest product, the CX24951, supports the newest DOCSIS standard, version 2.0 (see the DOCSIS Primer below). DOCSIS 1.0 has been around for about 3 years, and the industry moved to DOCSIS 1.1 early this year. The move from 1.0 to 1.1 was basically a software upgrade that added Quality of Service (QoS) and security to downloads. But there was no change to the PHY section and no improvement to the bandwidth of the modems. Recently, the standards committee ratified DOCSIS 2.0, which added new features to the hardware - a different modulation to the upstream PHY called Advanced Time Division Multiple Access (A-TDMA) and Synchronous Code Division Multiple Access (S-CDMA). These different modulations were supported by different companies and supporters for the two standards have been trying to prove that one was better than the other. However, Conexant sees them as very similar with different modulation schemes. Both have advantages, for example, in noisy environments S-CDMA has better impulse noise resistance and A-TDMA has better dynamic range. CableLabs approached Conexant to design the chips for a cable modem because both standards are designed for higher bandwidth and wider channels. The new modulation techniques significantly increase upstream cable bandwidth for data transmissions (up to 30 Mb/s) without requiring any physical rebuilding of cable networks. Conexant has been able to do the PHY technologies for many years. They decided to add both A-TDMA and S-CDMA to the chip. Competitors have not yet released their chip sets but Conexant has verified that the PHY works for both these standards. The part is in certification now for DOCSIS 1.1 and the company plans to ship in Q1, while DOCSIS 2.0 certification will be in Q1 2003 with shipping to follow in Q2. Conexant improved the performance and the processing power from earlier versions to 500 MIPS. The part uses two ARM processors - one doing the MAC processing in software and the other doing application processing. Comparatively, most CPUs shipped today by Conexant use either a 75 MHz ARM7 or a 120 - 130 MHz ARM9. This new chip is an almost 300 MHz ARM9. The chip is pin compatible with the older version so the only thing you need to have for the cable home device with a PCMCIA 802.11 card is a four-port switch. Conexant says they can create an integrated cable modem, like a gateway product, at a reasonable cost because it does not require a central processor. All of the cable modem functions can be placed on this one product, which is available in a 17 mm X 17 mm package. Conexant is putting 500 MIPS in a very small package for prices that are in the low $20 range (and lower once the product sells in high volume), which is less than the cost for a microprocessor that does the same thing. This product, with its advanced PHY for both TDMA and CDMA, has enough power to be used for many years and allows companies to use the extra MIPS for advanced features. The features that stand out for this product are the DOCSIS 2.0 feature that supports CDMA and TDMA, the number of MIPS for additional functionality, and the small size of the device. These indicate that the chip will be around for a while and it can be used in a cost effective manner. The CX24951 is available in sample quantities with volume production scheduled for the first quarter of 2003. It is packaged in a compact, 17 mm x 17 mm, 228-pin ball grid array (BGA) and priced at $21 in OEM volumes of 10,000 units. No data sheet was available when this product was reviewed but you can find the data sheet (when it becomes available) and more information under Broadband Modems.

DOCSIS Primer

The explosion in personal computing in the 1980s was followed rapidly by advances in computer networking technology. By the early 1990s, commercial on-line services, such as America Online and CompuServe, emerged to fill the need for information services for residential consumers using narrow-band analog modems. The ensuing leaps in computer networking technology and information science led to the "Internet age" of the mid-to-late 1990s, marked by the emergence of "killer-applications" such as e-mail and the World Wide Web. As residential consumers have become more and more reliant on the services provided on the Web, and as individuals have become increasingly interested in work-at-home alternatives to the networked office, the demand for a high-speed, reliable, and constantly available data service connection has risen significantly.

Cable is in a unique position to meet this demand. The same highly evolved platform that enables cable to provide telephony and advanced video services also supports high-speed data services. To date, the most successful and cost-effective means for providing data services is via cable modems that are compliant with the DOCSIS data-over-cable standard. According to Kinetic Strategies, Inc., Q4 2001 DOCSIS Cable Modem Shipments by Vendor report, by the end of 2001, more than 15 million DOCSIS-compliant cable modems had been shipped worldwide.

Cable Modems
Digital data signals are transmitted over radio frequency (RF) carrier signals on a cable system. For two-way communication, there is one carrier signal that carries data in the "downstream" direction (from the cable network to the customer), and another that carries data in the "upstream" direction (from the customer to the cable network). Cable modems are devices at the subscriber premises that convert digital information into a modulated RF signal in the upstream direction, and convert the RF signals to digital information in the downstream direction. Another piece of equipment, called a cable modem termination system (CMTS), performs the converse operation for multiple subscribers at the cable operator's head end.

Typically, a few hundred users can share a 6-MHz downstream channel and one or more upstream channels. The downstream channel takes the place of a single television transmission channel in the cable operator's channel lineup. It is compatible with digital set-top MPEG transport stream modulation (64 or 256 QAM), and can provide up to 40 Mbps. In the current generation of cable modems, the upstream channels use modulation formats such as QPSK or 16 QAM to deliver up to 10 Mbps per-channel. In the next generation, upstream channels will deliver up to 30 Mbps-per-channel. A media access control (MAC) layer coordinates shared access to the upstream bandwidth.

Cable System Upgrades
The cable platform has evolved into a hybrid digital and analog transmission system. Cable television systems were originally designed to optimize the one-way, analog transmission of television programming to the home. However, the underlying coaxial cable can support two-way signal transport. The growth in demand for Internet access and other two-way services has dovetailed with the trend within the industry to enhance existing cable systems with fiber-optic technology. Upgrades of cable plants have transformed cable systems into hybrid fiber-coaxial (HFC) networks. Replacement of a part of the distribution plant with fiber optics unleashed the inherent two-way capability of the coaxial plant, without the need to replace individual subscriber connections. Systems are being designed with fiber running out to "nodes" serving between 500 and 2,000 homes on average.

Cable Modem Applications
Cable modems have opened the door for customers to enjoy a range of high-speed data services, all at speeds many times faster than that provided by traditional dial-up telephone modems. In addition, the always-on nature of cable modems allows subscribers to be fully connected, 24 hours a day, to Internet services without interfering with cable television service or phone service. In addition, the broadband connection that the cable modem platform provides creates the foundation for many new services and applications that can only be dreamed about today. New services include:

• efficient multi-line "voice-over-IP" telephony
• impressive real-time interactive gaming
• high-quality, personal video-telephony
• on-demand, Internet-based delivery of entertainment programming.

DOCSIS Specifications and Standards
Cable companies and manufacturers came together formally in December 1995 to begin working toward an open specification. CableLabs coordinated the process, known as data over cable service interface specifications (DOCSIS). It has proven to be quite successful and has resulted in specifications that describe the communication between the cable modem and the CMTS. Leading U.S. and Canadian cable operators were involved, and these specifications have been formally approved as national, regional, and international standards by recognized standards-setting bodies such as the Society for Telecommunications Engineers (SCTE), the European Telecommunications Standards Institute (ETSI), and the International Telecommunications Union (ITU). The first effort under DOCSIS-the DOCSIS 1.0 specifications-included the best-of-breed technology available in the 1995-1996 time frame. The second generation-the DOCSIS 1.1 specifications-resulted in improved flexibility, security, and quality-of-service features. The third generation-the DOCSIS 2.0 specifications-is aimed at providing increased upstream throughput for symmetric services. Individual vendors are free to offer their own implementations with a variety of additional, competitive features and future improvements. CableLabs works with vendors and others on intellectual property rights issues to ensure a continuing supply of modems to meet the high demand.

For more information see CableLabs at http://www.cablemodem.com

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