Email Delivery

Receive new posts as email.

Email address

Syndicate this site

RSS | Atom


About This Site
Contact Us
Privacy Policy


November 2010
Sun Mon Tues Wed Thurs Fri Sat
  1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30        

Stories by Category

Basics :: Basics
Casting :: Casting Listen In Podcasts Videocasts
Culture :: Culture Hacking
Deals :: Deals
Future :: Future
Hardware :: Hardware Adapters Appliances Chips Consumer Electronics Gaming Home Entertainment Music Photography Video Gadgets Mesh Monitoring and Testing PDAs Phones Smartphones
Industry :: Industry Conferences Financial Free Health Legal Research Vendor analysis
International :: International
Media :: Media Locally cached Streaming
Metro-Scale Networks :: Metro-Scale Networks Community Networking Municipal
Network Types :: Network Types Broadband Wireless Cellular 2.5G and 3G 4G Power Line Satellite
News :: News Mainstream Media
Politics :: Politics Regulation Sock Puppets
Schedules :: Schedules
Security :: Security 802.1X
Site Specific :: Site Specific Administrative Detail April Fool's Blogging Book review Cluelessness Guest Commentary History Humor Self-Promotion Unique Wee-Fi Who's Hot Today?
Software :: Software Open Source
Spectrum :: Spectrum 60 GHz
Standards :: Standards 802.11a 802.11ac 802.11ad 802.11e 802.11g 802.11n 802.20 Bluetooth MIMO UWB WiGig WiMAX ZigBee
Transportation and Lodging :: Transportation and Lodging Air Travel Aquatic Commuting Hotels Rails
Unclassified :: Unclassified
Vertical Markets :: Vertical Markets Academia Enterprise WLAN Switches Home Hot Spot Aggregators Hot Spot Advertising Road Warrior Roaming Libraries Location Medical Public Safety Residential Rural SOHO Small-Medium Sized Business Universities Utilities wISP
Voice :: Voice


November 2010 | October 2010 | September 2010 | August 2010 | July 2010 | June 2010 | May 2010 | April 2010 | March 2010 | February 2010 | January 2010 | December 2009 | November 2009 | October 2009 | September 2009 | August 2009 | July 2009 | June 2009 | May 2009 | April 2009 | March 2009 | February 2009 | January 2009 | December 2008 | November 2008 | October 2008 | September 2008 | August 2008 | July 2008 | June 2008 | May 2008 | April 2008 | March 2008 | February 2008 | January 2008 | December 2007 | November 2007 | October 2007 | September 2007 | August 2007 | July 2007 | June 2007 | May 2007 | April 2007 | March 2007 | February 2007 | January 2007 | December 2006 | November 2006 | October 2006 | September 2006 | August 2006 | July 2006 | June 2006 | May 2006 | April 2006 | March 2006 | February 2006 | January 2006 | December 2005 | November 2005 | October 2005 | September 2005 | August 2005 | July 2005 | June 2005 | May 2005 | April 2005 | March 2005 | February 2005 | January 2005 | December 2004 | November 2004 | October 2004 | September 2004 | August 2004 | July 2004 | June 2004 | May 2004 | April 2004 | March 2004 | February 2004 | January 2004 | December 2003 | November 2003 | October 2003 | September 2003 | August 2003 | July 2003 | June 2003 | May 2003 | April 2003 | March 2003 | February 2003 | January 2003 | December 2002 | November 2002 | October 2002 | September 2002 | August 2002 | July 2002 | June 2002 | May 2002 | April 2002 | March 2002 | February 2002 | January 2002 | December 2001 | November 2001 | October 2001 | September 2001 | August 2001 | July 2001 | June 2001 | May 2001 | April 2001 |

Recent Entries

In-Flight Wi-Fi and In-Flight Bombs
Can WPA Protect against Firesheep on Same Network?
Southwest Sets In-Flight Wi-Fi at $5
Eye-Fi Adds a View for Web Access
Firesheep Makes Sidejacking Easy
Wi-Fi Direct Certification Starts
Decaf on the Starbucks Digital Network
Google Did Snag Passwords
WiMax and LTE Not Technically 4G by ITU Standards
AT&T Wi-Fi Connections Keep High Growth with Free Service

Site Philosophy

This site operates as an independent editorial operation. Advertising, sponsorships, and other non-editorial materials represent the opinions and messages of their respective origins, and not of the site operator. Part of the FM Tech advertising network.


Entire site and all contents except otherwise noted © Copyright 2001-2010 by Glenn Fleishman. Some images ©2006 Jupiterimages Corporation. All rights reserved. Please contact us for reprint rights. Linking is, of course, free and encouraged.

Powered by
Movable Type

« Foundry Upgrades WLAN Switch Software | Main | PDA for the Clumsy »

October 19, 2004

Why Cable Companies Have a Shrinking Pool

A thoughtful reader with no connection to cable companies thought my analysis of DSL versus cable service (in re: SBC's Wi-Fi hotspot offering) was a little harsh: This reader has had great cable modem performance, meeting the promised speeds. But I thought I'd share with you my response. Update: Folks more knowledgeable than I in the workings of the cable world have taken me to task: apparently there's more in common now with DSL and digital cable head ends than a few years ago--my knowledge on this subject is obviously out of date. I've revised this post.

When you buy into a pooled business service like Frame Relay, you can opt for a Committed Information Rate (CIR), or a rate below which the bandwidth will never be unavailable, but above that rate, you're not promised and you may often get higher rates. At one point, I had a 1.5 Mbps frame connection with a 384 CIR. I usually saw peak performance. But I was paying for a pool of bandwidth shared (virtually) with other users from other companies.

I believed that cable still had this same difficulty. However, digital cable head ends, or the points at which entire systems are connected (usually by optical fiber) out to neighborhood cable nodes which lead to hundreds of homes by coax, has much higher capacity and much greater ability to expand than I realized.

With DSL, the effective limit is the size of the DSLAM or DSL aggregator/multiplexer in the C.O. or central office. From the C.O. in most areas that have DSL, there's probably fiber back to the Internet, or something sufficiently high-speed to provide a large enough pool at that end.

So the pool that DSL users share could be higher because of the one-to-one DSL modem to DSL card in the DSLAM relationship. The pool that cable modem users share is at the neighborhood cable node, which limits the maximum amount of bandwidth that the cable companies can offer across the entire neighborhood shared network.

Where I erred in my analysis in this post was thinking that the cost and complexity of cable companies increasing bandwidth more than moderately as demand increased would radically outstrip capacity. But, as one reader, Mike Ritter noted, "It's an open issue if their bandwidth is more expensive to provide than DSLAM bandwidth. My guess is not."

Kerry Williamson brought up an excellent counterpoint to my one-to-one DSL argument, too: "Cable companies are able to provide exactly the same level of service everywhere within their plant [wire service area]. That LOCAL area plant can have a radius of 100 miles (I know, I have designed and built several of them), and have no effect on the service, either data or video. The telephone company and DSL cannot do that. The further from the CO, slower the service. Not so with cable." The more I read about this issue, it's certainly cable's greatest single advantage over DSL's current few mile limit for high-speed performance.

Williamson notes that current technology has the ability to offer in the U.S. 10 streams or pools of about 30 Mbps downstream and 10 streams of 3 Mbps upstream without any real difficulty using the widely adopted DOCSIS 2.0 cable data protocol. Each stream is a 6 megahertz wide (replacing the spectrum used for a broadcast television channel), offering a pool as large or larger than non-fiber-based DSLAMs in telco offices. DOCSIS 2.0 can run over 40 Mbps in the U.S., but at those speeds has much greater susceptibility to noise. (European broadcast channels are wider, providing more spectrum that can be replaced in the cable system by data, increasing bandwidth per stream.)

Williamson also notes that a new revision to the cable modem standard, DOCSIS 3.0, could bring 200 Mbps per stream downstream into the home. Here's an article in a broadband publication that details DOCSIS 3.0. Upstream speeds would dramatically increase, with 100 Mbps available per pool in the best-case scenario.

Byoung Jo Kim responded to the issues of whether there's more expansion left in DSL versus cable with this: "For DSL, the high rates achieved in South Korea and Japan are mainly due to their shorter lines and higher line qualities from denser and more recent deployments of twisted pair copper wires. In the US with the longer and older lines, it will be very difficult/expensive to achieve such rates just by putting in new line cards at central offices. Thus, even Bells are looking into wireless for reaching far-away houses that HFC [hybrid fiber coax] reaches easily, although the seriousness is questionable."

Kim points me to this reference: "A view of fiber to the home economics" by Frigo, et al, in Communications Magazine, IEEE (Aug. 2004, pages S16-S23, Vol. 42, Issue 8). (Only an abstract is available at no cost to non-IEEE members.)

Similar feedback on the DSL side, about high-speed DSL flavors coming soon--ADSL2 and VDSL, to name two--would be welcome. I've opened up comments on this post.

1 Comment

Well, except for the part that there are portable DSLAM's that SBC can drop in to an area for about $8000 total.

How much does it cost to upgrade a cable network again?