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Friday, June 14, 2002 |
I thought this would be of interest to readers. The title comes from a June 6, 2002 posting to the isp-wireless mailing list (http://www.isp-wireless.com) by Marlon Schafer of Odessa Office Equipment (http://www.ooe.com). Marlon is a Wireless ISP in Odessa, WA that is (deservedly) held in very high regard by the inmates... er, "audience" of the isp-wireless mailing list. Rather than co-opt Marlon's words, I'll refer readers to the archive version of Marlon's post at http://isp-lists.isp-planet.com/isp-wireless/0206/msg00863.html. Marlon's posting is well worth reading to get a sense of just how different the performance of the WaveRider equipment is from Marlon's well-developed 2.4 GHz Wireless Internet Access network in Odessa, WA.
WaveRider Communications (http://www.waverider.com) is a Canadian Broadband Wireless Internet Access equipment manufacturer. WaveRider's Last Mile Solution (LMS) product line operates in the 902-928 MHz ISM band. This is significant because 902-928 MHz has far superior foliage penetration characteristics than equipment that operates in the 2.4 GHz band. The relative lack of foliage penetration is a major factor in Wireless ISPs not being able to serve every potential customer who desires Wireless Internet Access service. To date, the 902-928 MHz band has been largely ignored by the vast majority of Wireless ISP equipment vendors (two important exceptions are Wi-LAN - http://www.wi-lan.com and the late, much-lamented Metricom who used the 902-928 MHz band extensively for user-to-poletop communications.) Largely ignored, because 902-928 MHz offers a smaller amount of spectrum in comparison to 2.4 GHz (26 MHz versus 83 MHz) and is 902-928 MHz is, for the most part, only available in North America (the 2.4 GHz band is nearly universal). I've long thought that with proper equipment, 902-928 MHz could easily be a "Wireless ISP Secret Weapon" in areas where Wireless Internet Access service is desired (customers waiting...) but 2.4 GHz equipment just won't penetrate. While there are many other vendors of 902-928 MHz data communications equipment (largely used for SCADA and other low-bandwidth telemetry applications), such equipment is largely inappropriate for Wireless Internet Access use. WaveRider's LMS product line is relatively new and hasn't been very extensively reviewed. As I state in my posting, I had some previous experience with 902-928 MHz equipment so had some basis for comparison.
On June 7, 2002, I followed up Marlon's posting with my own posting to isp-wireless:
Well, Marlon beat me to the keyboard, but he was about 200 miles closer to his than I was to mine at the end of the day.
I had to give Marlon a bit of hell because for his initial tests he had like 2/3 of the antenna taped up against the steel mast, and I knew on sight that was severely compromising anything resembling a normal radiation pattern (if not actually causing SWR and foldback of transmit power). Something that I didn't reveal to Marlon at the time was that I'd had some experience with 900 MHz gear, and I was fairly sure that what he was describing was not normal behavior for a 900 MHz system, which in general penetrates trees, houses, etc. pretty well.
For the tests we ran together, if we had mounted the base antenna up and in the clear better (something resembling a permanent installation) and away from the shading effect of the water tank, I think we would have had total saturation coverage at both ends of town where we lost signal.
Like Marlon, I was very impressed with the coverage (once we finally cottoned on to which end was front of the CPE panel antenna). TAKE THE HINT, WAVERIDER - PUT A LABEL ON THE FRONT! One thing I observed was that when we lost signal, it took a few seconds to recover, like the radio wasn't going to let the ping go through until it was "sure" that the signal had been re-established. In that time we had moved 10 feet or so. In a real-world test, the radio isn't designed to be mobile, so I don't count that "slow acquisition time" against it. In a real environment, you'd move the antenna around the room in various places to find the best signal, and then LEAVE it there.
A minor nit... the CPE panel antenna is very light in comparison to the relatively stiff, heavy coax cable. I can easily imagine the antenna getting pulled out of a window sill by the weight of the coax. I didn't get to see the entire system as it came in the box (Marlon pretty well stripped it down to essentials to take it on the road), but if there isn't a mounting frame that gives a bit of weight and stability to the panel antenna, there should be.
Another minor nit - the RSSI utility (constantly writing out the RSSI readings when in a telnet session) worked great, but the telnet session timed out way too quickly for our use in road testing... of course, it's designed as a quick test for optimizing the location of the antenna within the range of the length of coax (which is about 6' or so). So, I don't count that against them either, it just would have been nice to see RSSI readings continuously just like we were seeing the pings.
One last thing that I clarified with Mitch while on the phone. The cavity filter that WaveRider offers may not be necessary unless you're going to deploy in close proximity to paging transmitters AND you're going to run enough base stations that you'll need to use 5 MHz channels near the edges of the band. For Marlon's test we set it on 915 MHz and it worked fine... but there weren't any known paging transmitters nearby.
All in all, nice job, WaveRider. Please tell Bruce Sinclair that THIS was the product that I had REALLY wanted to see and hear about when WaveRider had their big public debut that I attended in Vancouver, BC in 1997 or 1998.
This final line of my posting warrants some additional comment. WaveRider first unveiled the idea for the LMS product line at a press conference in Vancouver, BC in 1997 or 1998 which I attended (it was sometime shortly after the debut of my Wireless Data Developments column in Boardwatch Magazine.) The nearly-ready-for-sale product that WaveRider announced at the time was a 2.4 GHz version of LMS. At that press conference, WaveRider spoke of the LMS product line eventually expanding into other license-exempt bands such as 902-928 MHz. I felt at the time, and (I think) stated this to WaveRider personnel that were present, that WaveRider's 2.4 product was entering a very crowded market for 2.4 GHz equipment, and that the announcement of a 902-928 MHz version of LMS, even though still in development, was more significant in the long term. In the years since, as far as I can tell, that early assessment has been borne out. WaveRider only began to gain notable success in the marketplace with the emergence of the 902-928 MHz LMS.
5:07:55 PM 
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http://www.80211-planet.com/news/print/0,,1481_1365071,00.html
Reporting from the 802.11 Planet conference in Philadelphia, Brian Morrissey writes:
Begin excerpt
At the 802.11 Planet Conference here, the message to the public hotspot market is: Forget John Q. Public, unless he's carrying a briefcase.
Analysts said the market for public hotspots, despite all the hype, doesn't appear all that large, except for niche providers for business travelers. According to Cahners InStat analyst Gemma Paolo, today there are just 41,000 hotspot subscribers. Even with that figure growing to 40,000 by 2006, the economics of the industry are difficult.
"For the pure plays, there's probably room only for a handful to survive," said Yankee Group analyst Adam Zawel. "We've been playing with the numbers, and then you've got all these players dipping in, and it just gets really thin."
End exerpt
I just enjoy the heck out of these types of stories proclaiming the inevitable death of the hotspot markets. I feel very strongly that the Public Wireless Access Points (PWAPs) will suceed and become totally ubiquitous in nearly every public area, and that, collectively many fortunes will be made. (That's not to say that every PWAP venture will succeed - far from it. There will be lots of casualties as there is a "dot com feeding frenzy" feel to this trend as way too much clueless, desperate-to-cash-in-on-the-next-big-trend venture investments are being pumped in.) I feel that every analysis of the PWAP trend that I have seen to date is very fundamentally flawed because they do not take into account the following factors:
- The cost of backhaul bandwidth to each every individual PWAP is assumed to be equivalent to the cost of a dedicated T-1 line. That assumption is fundamentally flawed. The primary requirement for a PWAP is that it offers some reasonable amount of bandwidth wirelessly; IE, a PWAP just turns on their wireless-equipped laptop, logs in / pays / automatically authenticates, and begins their Internet activity. That backhaul could easily be bonded dialup (roughly equivalent to 128 Kbps), ISDN (128 Kbps), DSL (up to 1.5 Mbps or faster), and most likely... wireless! (The last is especially true if the wireless backhaul is provided by a Wireless ISP with an existing network; the additional bandwidth demands of supplying a PWAP are a negligable addition to their existing customer base's bandwidth requirements.) All of these transports would provide more-than-adequate bandwidth to a PWAP at an order of magnitude lower cost than a dedicated T-1 line.
- The average PWAP customer uses a laptop to access the Internet. In 2002 and before, true. In 2003 and beyond, false. Current models of Palm's PDAs have a Secure Digital (SD) expansion slot, and SD 802.11b cards will soon appear. Once PDAs begin to ship with embedded "no pain" 802.11b (no significant change in form factor or battery life), I feel that PDA users will rapidly become the largest group of users for PWAP services. (This assumes that pricing and other business issues begin to approach reasonable - pricing for purely commercial PWAP service is way too high at the moment.)
- It's assumed that PWAPs are limited to "premises coverage". Bzzt. Bad assumption, extrapolated from typical 802.11b access point coverage which are specifically designed to limit coverage area - inefficient antennas, low transmit power levels, etc. 802.11b technology is easily capable of providing "much larger than premise" coverage. If such "wider coverage area" 802.11b access points are implemented, the pool of potential PWAP customers goes way up.
- We're now seeing the emergence of hot zones - coverage of outdoor areas such as public parks. We'll rapidly see the emergence of Hot Zones in places such as campgrounds, truck stops, marinas, private airports, gas stations, nearly anwhere someone would want to access the Internet (enabled in such places by alternative backhaul transport described above).
My standard disclaimer (modified): I consider this a significant development in the Broadband Wireless Internet Access industry. I've written extensively about this development, in significant depth in my newsletter Focus On Broadband Wireless Internet Access (http://www.strohpub.com/focus.)
3:09:32 PM
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The FCC has initiated Notice of Proposed Rulemaking (NPRM) FCC 02-180 to establish rules leading to the commercial use of the 71-76 GHz, 81-86 GHz and 92-95 GHz bands. The FCC's terminology for this spectrum is "W Band". What is unique about the W Band is that to date there has not been any commercial use (other than an experiment by Loea Communications) - an example of the fabled, long-thought-to-be-extinct "Virgin Spectrum". Among other approaches, the FCC will consider the possibility of making some portion or all of these new bands license-exempt.
My standard disclaimer: I consider this a significant development in the Broadband Wireless Internet Access industry. I will be analyzing this development in significant depth in a feature article in my newsletter Focus On Broadband Wireless Internet Access (http://www.strohpub.com/focus.)
Some pointers:
2:42:46 PM
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This is an interesting development. The technique of combining FSO and 60 GHz equipment in a near-perfect complement of license-exempt, capacity, range, and offsetting attenuation characteristics. That combination was first developed and used (to my knowledge) by e-xpedient in their Miami network. e-xpedient used Canon Canobeam FSO equipment, Harmonix GigaLink 60 GHz equipment, and Cisco switch/routers (with the routing / switching done in silicon to reduce latency to practically nil). I wasn't aware of any 60 GHz system vendors other than Harmonix, but a query to the company asking if they were involved resulted in a non-committal answer. Something of a confirmation that Harmonix is providing 60 GHz equipment to AirFiber is a single bullet point on a AirFiber white paper on the newly-announced system.
Now if the fiber backbone companies will just GRASP the concept of using high-bandwidth wireless for deployments in the last mile, instead of the ruinous "gotta run FIBER to EVERY customer, never MIND the cost" mindset.
My standard disclaimer: I consider this a significant development in the Broadband Wireless Internet Access industry. I will be analyzing this development in significant depth in a feature article in my newsletter Focus On Broadband Wireless Internet Access (http://www.strohpub.com/focus.)
For Immediate Release
AIRFIBER INTRODUCES NEW WIRELESS TECHNOLOGY COMBINATION; FIRST TO OVERCOME FOG, RAIN AND RELIABILITY BARRIERS
New Generation of Wireless Communications Eliminates Fog, Rain Concerns; Provides 99.999% Availability Over Longer Distances and Sets New Threshold For Reliability and Distance
SAN DIEGO - May 29, 2002 - AirFiber today unveiled a new high-capacity unlicensed wireless system that provides greater reliability over longer distances than ever before. Coupling carrier class free space optical (FSO) equipment with 60 GHz millimeter wave technology, the new solution provides continuous, error-free communications (up to 1.25 Gbps) and 99.999% availability over 1 kilometer - a capability previously not possible with any other unlicensed wireless equipment.
The new system, called HFR (Hybrid Free space optic/Radio), capitalizes on the complimentary nature of two respective technologies and dramatically extends their reach when coupled together. The reliability of an FSO link over long distances suffers during fog conditions, while 60 Ghz is limited in distance due to attenuation caused by heavy rain. However, the combination is virtually immune to the conditions that limit the distance of either technology alone - heavy rain does not significantly impact an FSO transmission while fog does not inhibit a 60 GHz signal. When the two technologies are coupled using AirFiber's patent-pending Redundant Link Controller (RLC), error-free wireless communications is possible in all weather conditions.
AirFiber intends for the product to address the telecommunications last mile problem, a dilemma that stems from the time and cost required for fiber extension and renders the vast majority of buildings worldwide without high bandwidth capabilities. AirFiber's products have the ability to reliably bridge this gap with a solution that is much less expensive than fiber, requires no expensive frequency licensing or permitting, and can be installed in hours rather than months.
"Other than changing the laws of physics, we have designed the only way to extend the reach of unlicensed wireless systems operating at high capacity," said Brett Helm, President and CEO of AirFiber. "This is a breakthrough that will revolutionize the last mile in telecommunications and unleash the pent-up capacity of installed fiber systems. The reaction among carriers has been incredible."
AirFiber's HFR system is unique and made possible by AirFiber's proprietary Redundant Link Controller (RLC), a technology currently available in the recently released AirFiber 5800. The RLC monitors two simultaneous transmissions (in the case of HFR, millimeter wave RF and FSO transmission), and provides a "hitless," or error-free, capability to the system. If interference occurs on one of the wireless links, be it from weather attenuation or any link blockage, the RLC maintains error-free communications by using data supplied via the other wireless link. This patent-pending technology is completely transparent to the network and occurs with absolutely no loss of data and provides a fiber-like quality to a wireless transmission.
AirFiber's solution is significantly different than previous attempts of marrying FSO with radio. HFR utilizes links running at the same bandwidth to provide a consistent and guaranteed data rate at all times during all weather conditions. This method is different than a microwave backup that would result in loss of data during the switchover and a dramatically lower capacity during fog events.
The AirFiber HFR system currently operates from 155 to 622 Mbps, with a 1.25 Gbps product to be available later this year. A white paper discussing the technology in more detail is available on the AirFiber Web site at:
http://www.airfiber.com.
About AirFiber
AirFiber is a leading-edge developer of free space hybrid access equipment, the telecommunications technology that wirelessly provides fiber-like broadband capacity at a fraction of the time and cost of installing fiber. AirFiber's products have been designed to adhere to the most stringent telecommunications carrier requirements to meld seamlessly into their networks and withstand the most rigorous of conditions. For more information, please visit the AirFiber Web site at www.airfiber.com.
###
For more information:
Geoff Mordock
AirFiber, Inc.
(858) 676-7000 x177
gmordock@airfiber.com
2:24:01 PM
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http://www.nytimes.com/2002/06/10/technology/10WIRE.html?ex=1024286400&;en=8bb397788ddf1bff&ei=5007&partner=USERLAND
Markoff writes about a new company called Etherlinx that has adapted commodity 802.11b components to create a Wireless Internet access system. Nothing new here from the perspective of the existing Wireless Internet Service Provider industry other than the quoted price point: "...they believe can be built in quantity for less than $150 each." It sounds very much like they have simply used the 802.11b radio and gutted out the 802.11b protocols and substituted their own homemade (or purchased?) software and protocols more suitable for use at longer ranges. Again, Wireless ISPs and WISP industry vendors already do this very routinely, at price points approaching that of Etherlinx.
On another level, this article is an example of the rampant cluelessness of the general business press about the existence of the Wireless ISP industry (sigh...) Markoff implies that Etherlinx' system will enable ISPs to provide new broadband wireless services. But...
- A very robust Wireless ISP industry already exists to which Etherlinx is simply "Yet Another Vendor",
- There are similar capabilities already on the WISP market from established vendors (though not at Etherlinx's stated price points (which are, at this point, purely hypothetical), and
- There's a lot more to providing wireless ISP service than just the existence of a suitable radio... like billing and authentication.
Note: For a few days at least I'll be trying to mention the developments of interest since the beginning of June. They won't be in chronological order. Ongoing, developments of interest will be posted as they develop and as I become aware of them.)
1:50:14 PM
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One of the more interesting capabilities of Radio Userland was a configuration line for setting up automatic checking of an email account for blog updates. That would be incredibly handy when attending conferences, travel, etc. It was a bit maddening to get it configured just right, but it's working now. I expect to make heavy use of this feature.
1:49:18 PM
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http://www.pbs.org/cringely/pulpit/pulpit20020606.html
Wow. How's this for an impressive introduction: There is a very good writer named Steve Stroh who specializes in wireless technology, and almost a year ago, he wrote an article that really disturbed me. Cringely refers to my now famous July/August 2001 article Part 18 RF Lighting: A Potential “Extinction Level Event” For Communications Users Of The 2.4 GHz Band (http://www.strohpub.com/0701feat.htm). Cringely puts his own spin on why he thinks that the "RF Lighting vs. 802.11b controversy" isn't getting much attention from the mainstream press. Unfortunately, he goes on to get a number of basic facts wrong about wireless technology which detract pretty significantly from the article. During the week preceding the article, Cringely called me and left a voice mail message saying that he had some questions. I return his call, leaving him a voice mail message saying I was happy to help. I also responded (in brief) to an email message from Cringely (under the assumption that we would talk that week). Unfortunately, he didn't return my voice mail, and it was disapointing to see Cringely's article appear with a number of factual errors. I emailed Cringely once again pointing out a couple of the more grevious errors and offered to go into more depth if he's interested. He wrote back and said that he is indeed interested in corrections and tentatively plans a followup column on this subject.
For those that aren't previously aware of Cringely, he's the author of an entertaining and informative book (which I read and enjoyed) called Accidental Empires: How the Boys of Silicon Valley Make Their Millions, Battle Foreign Competition, and Still Can't Get a Date and was later made into a PBS special titled Triumph of the Nerds. Cringely went on to do other projects in association with PBS, and now writes a weekly column found on PBS' web page (http://www.pbs.org/cringely.) Suffice it to say that Cringely has quite a following and his column is read regularly by a large base of fans.
So, at Cringely's invitation, I did write him back, and below is that message (with a bit of formatting).
Bob:
OK, you asked. I got busy and put it into draft, and got busy with other stuff. For your convenience, I include the relevant parts of the first two messages I sent to you on this topic, so you have it all in one place.
Again, thanks for the mention in your column. I'm a fan, and a regular reader, so it was quite a pleasant surprise. I got more (and more clueful) response from your mention than from the original slashdotting.
First, I don't claim any credit for "spotting" this issue way ahead of everyone else. Although I don't reference it in my article (but should have), I first learned of this issue, and the potential impact of RF Lighting on communications use of 2.4 GHz through a friend and colleague, Dewayne Hendricks. Dewayne referenced the Wall Street Journal article (that I did reference in my article) that first mentioned RF lighting in a very public way. Those mentions were the first I'd heard of a practical (remains to be seen, I guess) implementation of RF lighting. The WSJ article doesn't reference the 2.4 GHz band, but rather "out of band" emissions potentially interfering with satellite radio transmissions... and the "band" that such signals would be "out of" is 2.4 GHz.
Here are some of MY guesses as to the reasons that few have picked up (independently) on the RF Lighting / 2.4 GHz interference story:
- There are few RF Lighting devices actually deployed. The threat is mostly theoretical at this moment.
- When confronted, Fusion Lighting doesn't acknowledge the interference potential with communications use of the 2.4 GHz band
- The FCC can't restrict RF Lighting too tightly as it IS a legitimate use of the ISM bands under the Part 18 rules, so they won't "fuel" the "controversy".
- (Main reason) The vendors and industry associations don't want such a story written and downplay the issue. When reporters inquire, they get something like "it's always been a possibility, but there's no real news there" and the reporter moves on to the next big story.
Some background:
The original purpose of these chunks of spectrum - 902-928 MHz, 2.4 GHz, 5.8 GHz, was to be used for non-communications purposes. IE, it was INTENDED that they be "polluted" by things such as microwave ovens (2.4 GHz), plywood dryers, diathermy machines, RF lighting, etc. The formal name of these bands - Industrial Scientific and Medical - ISM pretty well explains the intent of the FCC.
When the computer folks came along 15 or so years ago begging for some relatively large chunks of spectrum and requested to use that new spectrum without the need for conventional FCC licensing (so the gear could be sold over-the-counter), the FCC said, in effect "OK, how about you use the ISM bands?
- IF you use low power,
- IF you use spread spectrum (which the FCC wanted to encourage / see experimented with, just having been declassified),
- IF you swear that you have NO expectation of protection when interference inevitably happens...
then we (the FCC) agree that you don't need to get a usage license for each unit.
There are other complications, like there being LICENSED (therefore higher priority than Part 15) users given rights in the ISM bands, but those are the basics of the "conflict".
How we may well have reached an inflection point is that to date, the industrial devices operating in the ISM bands (under Part 18 rules) have only "caused interference" very locally AND the economic value of communications use of the ISM bands has risen exponentially. It's my guesstimate that the "economic activity value" of the license-exempt bands is immense compared to almost any other chunk of spectrum except perhaps cellular / PCS phones (and that's arguable) and Digital Satellite TV band. RF Lighting may upset this delicate balance by "radiating interference" (and that's technically inaccurate, but gets the point across) from a high point (75' light pole) in a populated area (a large parking lot) surrounding which there may well be homes or businesses making considerable use of 802.11b and other license-exempt wireless systems.
All the professionals in this industry have known this delicate state of affairs from the very beginning. But the consumers had no clue other than the common wisdom that "your microwave oven might interfere with your household WLAN". It's simply not in the interests of the wireless equipment vendors to say "this wireless LAN device could stop working at any moment due to interference issues. You have no recourse if you encounter such interference - you must accept it."
Yet accept it they must. There's a tag that's supposed to be attached to EVERY Part 15 device that says (paraphrased), in part, "This device must accept interference, even when such interference causes undesirable operation." Everyone seems to have a problem with this. It basically says buyer beware, you have no recourse. But the vendors don't explain this in depth (again, it's not in their interest to do so and scare off potential customers).
My article of a year ago that you cited wasn't intended to chastise Fusion Lighting. They have a device that uses RF technology, they went to the FCC to find out where in the spectrum such devices are supposed to operate, and the FCC steers them to the ISM bands. This is just an example of the law of unintended consequences.
The FCC never, in their wildest fantasies, scenarios, or outright speculations, could have imagined that unlicensed uses of spectrum would become SO popular, to the point of eclipsing many licensed uses of the spectrum (I could cite lots of examples of this.) The FCC simply isn't attuned to Moore's Law yet as it applies to wireless spectrum, yet the force that's driving this vastly increased use of license-exempt spectrum are the increasingly capable DSPs that can recover signals too low to even be heard by equipment as recent as 5 years ago, faster cheaper processors that can use much more sophisticated (computationally intensive modulation techniques like OFDM, and cheap RAM to enable things like mesh networking to be able to store routing tables, etc. in the radio.
In regards to your story about your buddy Steve's experiences with BroadLink, BroadLink doesn't have to care about what happens to other Part 15 users as a result of their system's operation. As long as BroadLink's systems are in compliance with the letter of the Part 15 rules, they're golden as far as the FCC is concerned. The FCC takes NO position about Part 15 vs. Part 15 clashes (nor Part 18 vs. Part 15 clashes.) There's no language in Part 15 about "thou must play nice and share the spectrum with fellow users". The ONLY thing the FCC cares about is if you're within the letter of the law of Part 15; your equipment is certified as a system, etc.
That your buddy Steve and BroadLink have issues doesn't trouble the FCC at all. That phrase attached to nearly all (by law, SHOULD be >ALL<) Part 15 devices about not causing harmful interference has a very specific meaning in FCC Legalese - it specifically refers to not causing interference to LICENSED spectrum users. Since Part-15 anything isn't licensed, and part of operating under the Part 15 rules means "must accept interference, even when such interference causes undesirable operation".
This was WELL established with Metricom's original (902 - 928 MHz band) and 128 Kbps Ricochet network (began using 2.4 GHz band for node-node linking). When Ricochet came online in San Francisco, it caused a lot of old, not very robust 900 MHz gear to stop working. Same thing for other markets - Seattle, Washington DC, then San Diego, etc. So sad... but the Part 15 rules offer NO protection. So, use of the license-exempt spectrum continually evolves. Old equipment gets retired, replaced by newer equipment that is more robust (and works better anyway). I call this the "Darwinian Nature of License-exempt Wireless."
If you want more background on RF Lighting versus communications use of 2.4 GHz, I wholeheartedly recommend that you talk to: (referral was deleted for weblog publication)
A few nits to pick with factual inaccuracies and mis-characterizations in your article:
- RF lighting dumps a lot of "interference" onto the 2.4 GHz band in its immediate vicinity. SOME types of modulation CAN effectively deal with such interference. Stating very generally, Frequency Hopping Spread Spectrum (FHSS) will deal with such interference better than 802.11b. (By no means am I saying that FHSS is always better than DSSS as used in 802.11b. Which is better depends on specific cases.) Some vendors have implemented VERY robust FHSS techniques and I mention one in particular in my article - WIMAN Systems. WIMAN's systems are used to good effect by Wireless ISPs in some very, very "RF polluted" areas such as Mexico City and Puerto Rico. There are others, but I won't make this into an endorsement.
- 802.11b = Wi-Fi. Wi-Fi is only a trademark / logo that certifies that equipment bearing it interoperates with other Wi-Fi equipment. There were no "older" versions of Wi-Fi. Wi-Fi came to life only with the advent of 802.11b.
- 802.11 used three physical transports - 2.4 GHz Direct Sequence (compatible with 802.11b's 1 Mbps and 2 Mbps modes), 2.4 GHz FHSS (totally INcompatible with 802.11b), and Infrared (a bit of trivia). 802.11 didn't catch on because the equipment was expensive, few people had a requirement, and interoperability couldn't be assumed. It was perfectly possible to buy two pieces of 802.11 equipment, and they be totally non-interoperable.
- FHSS until VERY recently was required to use ALL of the 2.4 GHz band, so as not to "monopolize" any specific part of the band- the RF energy had to be spread pretty equally over the entire band. The Part 15 rules were changed in May, 2002 to allow adaptive hopping (at much reduced power levels).
- Hedy Lamarr's patent was actually a communications technique to prevent Germans from jamming the radio signals that allowed torpedoes to be remotely controlled, and thus more deadly. The intent wasn't encryption per se, but rather "jam-proofing". The patent was co-authored by George Antheil.
- All of the 802.11b speeds - 11 Mbps, 5 Mbps, 2 Mbps, 1 Mbps, use Direct Sequence Spread Spectrum and a 22 MHz channel. The modulation is progressively more robust (longer range, more tolerant of interference) as the speed steps down - 5.5 is better than 11, 2 is more robust than 5.5, etc.
- The UNII 5.8 band and the 5.8 ISM band are mostly the same chunk of spectrum. Equipment vendors can choose for their equipment to operate under the UNII rules or the Part 15 rules. The downside is that 5.8 is subject to ISM use - conceivably we could see RF lighting show up at 5.8 GHz also. But most of the Wireless LAN activity is down at 5.3 GHz which IS pretty much "virgin spectrum" for communications use only.
Over the next few years, we're likely we'll end up using a combination of license-exempt spectrum at 2.4 (802.11b, 802.11g), 5 GHz (which may well grow from 300 MHz to a total of 525 MHz), and other exotic spectrum and techniques like 60 GHz (a total of 7 GHz of spectrum to play with there), Ultrawideband, and even Free space optical (lasers). We'll use multimode radios, and mesh networking. We'll also use some variant of 3G cellular data technology, but to date, only one company, Monet Networks, is doing 3G data RIGHT... so I'm not yet counting on 3G data being any kind of a success.
Thanks,
Steve
1:38:19 PM
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© Copyright 2002 Steve Stroh.
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