By Richard Nesin, president, HomePNA
The big HomePNA news this week (and I hope you read Monday’s blog so you know what I am talking about) was CopperGate’s announcement about the Shanghai Engineering Research Center for Broadband Technologies & Application (B-STAR) selecting HomePNA-based technology as its primary solution for its Multi Dwelling Unit (MDU) interactive Digital TV test program in Shanghai. Why didn’t they select DOCSIS like so many other cablecos? In a word, cost. HomePNA technology combined with fiber to the premises (FTTP) gave them the right mix of performance and features without the large price tag.
First, a little background on DOCSIS. The Data Over Cable Service Interface Specification or DOCSIS is an international standard developed by CableLabs, the cablecos’ R&D consortium. DOCSIS, like HomePNA, is an ITU standard although the work is done in Study Group 9 (SG 9) and is completely independent of the G.hn and HomePNA home networking standardization work being done in SG15.
DOCSIS defines the protocol for high-speed data transfer over an existing Cable TV system. The killer application, needless to say, is Internet access and there are a large number of DOCSIS cable modems sold worldwide (especially in North America). The first DOCSIS specification was released over 10 years ago. The most recent version, DOCSIS 3, adds support for IP – that is to say Internet Protocol version 6 (IPv6) - to the standard. Multiple versions of DOCSIS exist around the globe such as EuroDOCSIS to comply with differences in regional standards. CableLabs and other organizations perform DOCSIS equipment certification testing on a regular basis.
DOCSIS equipment consists of the cable modem installed in your home and a cable modem termination system (CMTS) located at the cableco’s “headend”. It’s not cheap for an MDU. A DOCSIS cable modem has to be installed in each apartment and connected to it’s corresponding port on the CMTS over the cableco’s coax/fiber (called HFC for hybrid fiber-coax) cabling. The CMTS connects the customer’s DOCSIS modem to the Internet.
For those of you who (like me) had early DOCSIS 1.0 modems that required a phone line connection in addition to the coax connection to operate, you've probably guessed this isn’t the entire story. When I first got broadband the only option was this DOCSIS kluge (kluge is an engineering term for a less than elegant system). I had to get a second dedicated phone line (remember phone lines? They are what DSL modems use today for Internet access, VoIP and IPTV) from the phone company in order for my cable modem to work. Cablecos had to upgrade their HFC network to provide a return path for upstream traffic – data sent from your PC to the Internet – over the coax. This also costs money. While many cableco’s HFC networks have been upgraded, there are parts of the world where the technology lags.
What's it all mean? Stay tuned for the next post.