Electronic Design

Home-Networking Scheme Takes Advantage Of Existing Installed Coax

Wireless is the hot ticket to home networking, but it's just one of many different methods out there. For instance, a new option uses the installed cable-TV coax in your home. It serves up probably the best wired arrangement, because coax has the broadest bandwidth of all—over 1 GHz.

The c.LINK-270 created by Entropic Communications makes such a network possible. It can be used to implement set-top boxes for consumer electronics equipment, network interface cards for PCs, or new forms of multimedia data distribution (see the figure).

The EN1010 is the RF front end that attaches to the standard 75-V RG-6/U coax cable through a filter and balun. This chip employs an external 25-MHz crystal and sets the frequency of the network signals on the cable bandwidth, typically in the 500- to 1500-MHz range. It uses a modified form of orthogonal frequency-division multiplexing (OFDM) that spreads the signal over a 50-MHz bandwidth and provides modulation options for a data rate up to 270 Mbits/s.

The CN2010 baseband chip handles all of the networking functions. It has an external serial EEPROM, and it interfaces to a host processor via a PCI bus. Also included is the logic to provide data-rate adaptation from 20 to 270 Mbits/s. Furthermore, it incorporates hardware DES encryption for privacy and IEEE 802.1p priorities to support the quality of service necessary in entertainment applications. Up to 10 simultaneous c.LINK channels are supported. And, there are hooks for adding digital rights management. A software development kit is available.

Though the c.LINK chip set's primary application is consumer home-entertainment networking, another secondary market involves the connections that are part of multiple-dwelling units and fiber-to-the-curb (FTTC) systems. New FTTC networks are being installed now, but many will use Ethernet, DSL, or some other networking scheme to get from the fiber termination to the home in the last 500 feet. That's where the c.LINK method steps in as an alternative.

The protocol implemented in this chip set was developed, and is supported by, the Multimedia over Coax Alliance (MoCA). Companies within the group include Cisco, Comcast, Echostar, Entropic, Motorola, Panasonic, Radio Shack, and Toshiba. These companies also will provide testing and certification services to ensure interoperability.

Chips are available now. Pricing varies depending upon the volume and application. Contact Entropic directly for details.

Entropic Communications
www.entropic-communications.com

Multimedia over Coax Alliance
www.mocalliance.org

TAGS: Toshiba
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