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

« Bigger Fish | Main | Evolution of a Case: Darwin Networks »

May 14, 2002

Hendricks: Licensed Users and Unlicensed's Future

We start with an interview with Dewayne Hendricks, and follow it with a response from Steve Stroh.

Dewayne Hendricks, Elaborated

FCC technology adviser Dewayne Hendricks has appeared in the press lately to be obsessed with illegal Wi-Fi antennas. As I noted on Sunday, I suspected Hendricks had a broader message which was elided.

I spoke to Hendricks Monday morning, and he confirmed that while not misquoted, he has been edited down to soundbites that make him sound like an antenna zealot. In fact, Hendricks's concerns about the future of the unlicensed use of spectrum stem from broader FCC policy decisions and licensed co-habitants of the unlicensed bands.

Hendricks is the CEO of the Dandin Group, a member of the FCC's Office of Engineering (OET) Technological Advisory Council (TAC), and the chair of the TAC's spectrum management working group.

The Dandin Group has an agreement with the Royal Kingdom of Tonga which allows them to test and deploy new technologies that incumbent users in other countries would prevent. "We can do whatever we want in the radio spectrum there" as a licensed common carrier. The kingdom is a test-bed where Dandin can offer to "bring your technology here and you can try it out in a real market." Ultrawideband (UWB) is one of the technologies for which Hendricks is interested in providing an effective testing ground.

Hendricks said that most unlicensed uses of the 2.4 GHz (2.4000 to 2.4835) band are unaware that there are four licensed uses of the same band. These other uses haven't overlapped significantly in the past, but the rise of use of licensed users may change the availability of this unlicensed spectrum.

Wi-Fi, Bluetooth, cordless phones, and a number of other devices are categorized under Part 15 of the FCC rules. Part 15 defines the characteristics of devices; the FCC individually approves Part 15 devices for use, but no license is required by purchasers to operate. Part 15 devices are limited to various spread-spectrum modulations to ensure that no one frequency in the range is occupied for very long. Power limits also ensure that signals can penetrate only limited distances.

In contrast, the four licensed uses of parts of the 2.4 GHz band can use more power, and have more rights. These licensed uses include amateur ("ham") radio and television (Part 97, overlapping 2.400-2.450 GHz), and three others that overlap 2.4500-2.4835: Part 101 fixed point-to-point microwave; Part 74, which Hendricks says is used for electronic newsgathering, such as local video uplinks; and Part 90, which Hendricks says many municipalities are using for police surveillance links. (In double-checking this information via the FCC's site, I found that many of these services can operate across many dozens or hundreds of frequencies, and most of them have many distinct purposes in addition to the specific uses cited by Hendricks.)

Roughly, the amateur radio/TV overlaps 802.11b channels 1-6, and the other three services, channels 7-11. HomeRF and Bluetooth hop across the entire available range so would be potential interferers across all four services.

Hendricks said, "All of those licensed services, if they're interfered with, can start an interference action with the [FCC], which can result in the unlicensed user being shut down." The sole case Hendricks can cite happened in early 2001, when Darwin Networks was contacted by the FCC because of a complaint by local hams. The ARRL, the ham's national association, reported on the story, but extensive searches through their archives and on Google cannot find the resolution, despite the initial attention. Darwin Networks no longer appears to be in operation. Hendricks spread the news about the FCC's request for information from Darwin in a few forums at the time, noting it as a potential harbinger.

Hendricks said that the lack of enforcement questions and actions doesn't predict the FCC's future behavior. I asked him if this were a Challenger shuttle-like situation, in which the current status quo had lulled unlicensed users into a state of complacency. He agreed with that statement.

Hendricks pointed out a simple case in which hams could shut down an extensive area. "Ham television is becoming more and more popular, the equipment's becoming cheaper; lots of hams like to broadcast," Hendricks said. "It's a pretty sexy application."

Hendricks said that the San Francisco Bay Area already has a number of ham TV repeaters. "A bunch of hams could deploy TV broadcasts" up to 1.5 kilowatts (kW). "We could effectively shut down 802.11 in the entire Bay Area, and it would be perfectly legal and there wouldn't be anything you could do about it." Part 15 devices like Wi-Fi radios are limited to less than 1 watt (W), and many devices use 30 to 100 milliwatts (mW). (When you start talking about radiated power output, these numbers are only starting points for calculations.)

Hendricks is pushing for a solution in his advisory role to the FCC to ensure that unlicensed spectrum is preserved. But, he says, "To deal with the situation effectively, you've got to start" dealing with the truth of the situation, including the licensed spectrumholders' power.

The FCC may offer up a new plan, as of yet unknown to deal with congestion. Hendricks said, "What happened in the first term of the TAC, when we presented our findings on the interference and congestion in the unlicensed bands," the FCC said it would be under a new regulatory framework.

Hendricks also noted the existence of a little-known intra-executive branch body known as the IRAC (Interdepartment Radio Advisory Committee). This body, which operates in closed meetings, coordinates governmental agency use of spectrum, and recommendations coming out of the IRAC virtually always set the agenda for spectrum use. Hendricks said, "They operate as a Star Chamber. They meet in secret and there is no appeal to their decision."

The group "has been around so long that they don't really think about what's in the public interest; they think about what's in the agency's interest," Hendricks said. This tends to reinforce the status quo.

Hendricks divides the noise surrounding 2.4 GHz and unlicensed spectrum use into two piles: real threats from licensed users, which he hopes can be mitigated by future modification of rules; and political static from the incumbent telephone companies and other data providers who "are coming to the commission and saying, look, we're going to be paying all this money for 3G spectrum" and yet facing competition from unlicensed users.

The paradigm shift underway will leave those incumbents behind, Hendricks says. "Incumbents hardly ever make the shift because they don't learn the new language of discourse." Steve Stroh has said that he believes a murmur campaign is mounting in political circles to try to derail unlicensed wireless networks. In the June/July Cook Report on the Internet, Stroh wrote, "There is considerable anecdotal evidence that there is a widespread, and perhaps coordinated campaign underway to discredit BWIA [broadband wireless Internet access] in general (and in particular license-exempt BWIA systems and companies) with the effect of starving out BWIA vendors and service providers for investment capital."

Hendricks uses real property to make the example of how spectrum is currently used. AT&T buys a house, but they have to share it with other people. A key service is the bathroom. If a house sharer (unlicensed user) is in the bathroom when AT&T needs to use it, AT&T can kick them out. But if the lower-priority guy takes a few minutes to clean up and get out, AT&T can call this interference.

Instead, Hendricks pushes what he calls the "post-Shannon" model in which many services can overlay the same bandwidth, which sidesteps Shannon's Law. In this scenario, AT&T owns the house, but they're not aware that anyone else is there. With UWB, Hendricks said, "I'm not only using the house, but other houses in the neighborhood."

Hendricks is optimistic about newer technologies overcoming the regulatory mess, but these protocols won't emerge first in the U.S. "The real developments are not going to happen in the developed countries because of the incumbent issues," which is why Hendricks is working in Tonga.

My analysis of Hendricks remarks: he's clearly not an alarmist, and as someone with a deep technical and policy knowledge is speaking from experience. He said several times during our interview that his advisory role on the FCC committee requires that he and his colleagues spin out reasonable scenarios as they offer guidance that the FCC can choose to use in charting courses that allow for new technology to get the bandwidth they need.

But when the challenges start coming, regardless of the licensed users actual rights, will the FCC take the politically damaging course of shutting down public networks, community networks, and corporations networks. (Remember: if 3Com is interfering with a ham operator, the ham operator wins.)

It seems unlikely, but I'm not an inside the Beltway guy, no do I know how the FCC conceives of and interact with the markets. The most obvious course as we head toward the future is that the billions and billions of dollars representing companies that make, sell, and employ Wi-Fi and related equipment today will have the lobbying power and the public sentiment to push for changes that accommodate all users.

This changeover could be painful, but we have to ask: would the FCC even conceivably shut down all Wi-Fi or all public unlicensed networks? Will they consider the public interest as they move forward? Will open forums allow the discussion of these issues to the benefit of individual, groups, consumers, businesses, educational organizations, and other entities?

I'd personally like to see what happens when a ham tries to get the FCC to enforce an action against Microsoft's campus-wide Wi-Fi network.

Hendricks likes to point to Citizen's Band (CB) radio. Initially, CB required a license to use, but consumers purchased radios in large quantities, and the FCC had to make a decision. "The FCC was unsuccessful in dealing with the Citizen's Band," Hendricks said. "They just walked away from it." This left the citizen in charge -- which is how it should be for unlicensed spectrum as well.

Small update: Hendricks wrote in after reading this to note that he'd been attending Spectrum and Services Beyond 3G the last few days, where four FCC bureau chiefs were also in attendance. There was the announcement at the meeting that a new unlicensed band may be launched with different parameters to allow for more exploration.

Steve Stroh on Bandwidth Congestion and Overlaps

Steve Stroh generously responded at length with further elaboration and some critique of my analysis -- which I welcome! Here is his reply to Sunday and today's items.

Not all, or even most (yet) of the use of 2.4 GHz is with 802.11b/g and a, and I think it is erroneous to extrapolate the likelihood, or not, of a "tragedy of the commons" from that perspective.

The bigger picture: The 2.4 GHz bands are far, far more utilized than just with 802.11b used in Wireless LANs such as hot spots and enterprises. For example, Wireless Internet Service Providers are a major user of 2.4 GHz, and in their markets (mostly secondary and rural) they are a competitive provider of, if not the only source of Broadband Wireless Internet Access. There are markets where there are as many as six or more Wireless ISPs operating Metropolitan Area Networks (MANs) operating base station/Customer Premise Equipment that can achieve ranges between customer and base station of as much as 20 miles.

For example, in San Diego County, CA, the San Diego County Sheriff department has deployed a network of base stations that allow 1 Mbps intrAnet (note -- not Internet) access from each of their 650 patrol vehicles - using the 2.4 GHz band.

I view it as likely that 802.11b access points will be widely deployed in a similar fashion to Metricom's Ricochet network -- on streetlights and other "high, but not too high" structures to provide metropolitan area network coverage. There are already such deployments in operation.

Indoors, there are untold numbers of wireless devices using 2.4 GHz, and there is no requirement to use 802.15.x, 802.11, 802.16, or indeed any specific protocols that "politely share" usage of the 2.4 GHz band. There is also the looming issue of industrial uses of 2.4 GHz -- remember that the FCC designation of the 2.4 GHz and other license-exempt bands is Industrial, Scientific, and Medical, operating under Part 18 of the FCC rules. Part 18 devices, such as RF Lighting that you've already written about, doesn't have any requirement to "politely share" the 2.4 GHz band.

High power: There is no requirement that Wireless Access Points (WAPs) be restricted to the low power levels that most currently operate at. Much higher power levels are possible, and such (completely legal) "high power WAPs" are now routinely being deployed. This is why there could be much more interference -- a "street level WAP" could easily transmit signals well into buildings. In previous articles, you've noted that this is already happening in downtown San Jose, where a number of service providers are providing commercial 802.11b Internet access in "zone" coverage. While those service providers can and should cooperate between themselves, having only three non-overlapping channels for 802.11b does not allow much "room" for in-building WAPs to operate in "competition" with those service providers' systems.

The unfortunate tendency, proven all too often in real world experiences, is that in the face of such competition, using higher power is a solution of choice. This fear has been borne out in some countries, where there is weak enforcement of "low power" rules for equipment and deployment in the 2.4 GHz band -- a very real 2.4 GHz tragedy of the commons.

FCC Enforcement: While it is certainly true that the FCC can find and shut down illegal high power Part 15 systems, they do not have the ability -- manpower, budget, or mandate to investigate more than a token few violators. That's just the reality of the situation. I and others think that the FCC should have "spoken up" in the case of well-publicized news stories about illegal Part 15 use, but they didn't, and I think that lack of action will haunt them in the years to come.

You wrote, I'm optimistic: people may crowd the beach, but they're not masochists. Would you put your umbrella and blanket down if you knew that every minute a volleyball would land in your picnic basket and someone would run right over you pursing an errant child? Probably not. The beach that's so busy people don't go there has worked out an informal system of usage that preserves its common function. The cost: privacy and solitude. The benefit: society and common use.

The worst part of the tragedy of the commons scenario is that the average buyers of license-exempt systems don't know ahead of time about "volleyballs landing," so they buy the equipment, try it, interference results (both the new and to existing equipment), and the new equipment owners take it back for another unit because "it doesn't work." In the meantime, the 802.11b network of the folks next door "goes on the fritz" and they assume that it's stopped working. This effect is occurring more and more frequently.

The Part 15 vendors are in "sell, Sell, SELL" mode - very aggressive competition. I'm told that some have (illegally) moved the required "... must accept interference" notice from the device itself to the instruction booklet which few bother to read, likely so that the prospective purchaser is less likely to read the notice. It may be that the FCC requires vendors of consumer products to post the "... must accept interference" statement on the exterior of the packaging, in a certain size, like is done now with cigarettes and alcoholic beverages. But there will undoubtedly be resistance to such a warning -- the vendors aren't anxious to admit to potential customers that the tragedy of the commons scenario may come to pass. They just want to sell more Part 15 devices, and spooked customers won't buy many. The market will certainly correct this problem, as is happening with 2.4 GHz cordless phones being returned because they "don't work" when the problem was an interference issue with the units in the surrounding apartments.

No easy solution: What's made the 2.4 GHz bands such an unprecedented success is that new wireless products can be brought to market without regard to their potential to impact existing 2.4 GHz systems already in place. Got a new idea? As long as it's certified to meet the minimal requirements of Part 15 rules, any new product can be offered for sale. To me, this is a primary reason why the tragedy of the commons is, to some extent, a plausible scenario.

What do I think? After the above points, it's probably reasonable to conclude that I believe that a tragedy of the commons will occur in license-exempt spectrum. While I understand the arguments for that scenario, I don't believe that the license-exempt bands will become unusable. I've evolved a (somewhat controversial) theory that increased crowding of license-exempt spectrum and the FCC's requirement that Part 15 systems "must accept interference" have birthed a rapid "Darwinian evolution" in license-exempt systems.

You espouse the idea that future systems will "all just get along" with new protocols being proposed. I'm skeptical that such protocols will be sufficient; such protocols only work when all systems use the same protocol. It seems unlikely that a Part 18 plywood dryer could be made to "just get along" with nearby Wi-Fi systems. But I do believe in market forces, and if the FCC can resist the temptation to mandate a "spectrum sharing etiquette" for license-exempt spectrum, and the pressures of licensed uses of the same spectrum remain, then the market approach will be able to function. That is, the best wireless technology will "win" -- continue to function in the presence of interference. Such "robust" systems will begin to sell well, because they will continue to provide service when less-capable systems cannot function. We're seeing the beginnings of such Darwinian evolution now, in vendors that offer only older, less robust, less cost-effective wireless technology going out of business because few will buy their products.

The counter-argument, that the license-exempt bands should be reprioritized to favor "less robust, but cheaper and more widely used" systems such as 802.11b / DSSS modulation, would be, in my opinion, a major policy mistake. Doing so would fossilize the use of license-exempt spectrum into the same kind of slow, compatible evolution and eventually stagnation that we've come to observe from licensed spectrum. In licensed spectrum, there's very little market incentive to develop and deploy new technology that accommodates more users, is more cost effective, allows higher speeds, etc. (despite what the wireless auction economists state).

New technologies are emerging in license-exempt spectrum. FHSS, for example, was chosen by HomeRF and Bluetooth and a number of Wireless Broadband equipment vendors because it is much more robust in the presence of interference and arguably scales better. For example, while 802.11b equipment might be unusable in countries that don't effectively regulate license-exempt spectrum, certain vendors' equipment will continue to operate in the presence of such intense interference. It will be interesting to see how OFDM, PBCC, and other wireless technologies such as adaptation of cable modems for broadband wireless use fare in the presence of vastly intensified usage of license-exempt spectrum.

In summary, I think that as long as there is ample incentive for rapid evolution in technology in license-exempt spectrum, a tragedy of the commons will be avoided because better, more robust systems will continually emerge. But, if the incentive for such rapid evolution is removed, the result will almost certainly cause a tragedy of the commons in license-exempt spectrum.

Other News for 5/14/2002

D-Link shifts to Texas Instruments: D-Link and TI announced that D-Link will use TI's ACX100 chips in new products in its wireless line-up. The companies claim a 30 percent throughput improvement over competitors, along with greater speeds at longer distances. Although this chipset supports the someday-to-be-ratified 802.11g optional PBCC modulation (developed by TI), the press releases don't mention a 22 Mbps mode. Hopefully, they'll clarify whether a firmware upgrade will make the D-Link models 802.11g compliant when the spec is ratified.