Unintended Consequences of High-Efficiency Lighting
By Steve Stroh

A new type of lighting system called "Radio Frequency, or RF Lighting" is being developed. It is claimed that RF Lighting devices will consume much less electrical power for an equivalent amount of light than current lighting technologies. The potential power savings of RF lighting came to prominence during the California power shortages in Summer 2001.

RF lighting works by eliminating the need for a filament or electrode, or a "raw" electrical discharge as is the case with current lighting systems. Instead, the "excitation" of light-producing elements is done with radio frequency energy instead of electrical energy. In addition to substantial energy savings, other claimed potential benefits of RF lighting are much longer lifetimes, and no change in color or brightness over the lifetime of an RF lighting system. For more information on the technology of RF lighting systems, see http://www.fusionlighting.com/technology.htm.

The Interference Problem

There is a potential problem with RF lighting, especially in multi-tenant buildings, that building managers and developers should be aware of. The radio frequency energy used in RF lighting systems is emitted within the popular 2.4 GHz band used by, among many other devices, wireless Local Area Networks (WLANs, often referred to as "Wi-Fi" devices) and the newest generation of cordless phones. Tenants who are using such devices may well find them completely non-functional if building management (or other tenants) install RF lighting systems in close proximity to tenant areas.

WLANs and 2.4 GHz cordless phones are proving to be very popular among technology-savvy consumers. With multiple-computer households becoming more common, the need has arisen to share high-speed Internet connections, printers, and other devices between members of the household who each have their own computers. WLANs, while not exactly "easy" to set up, are easy enough that they're proving to be a popular solution to the "computer sharing" problem. The primary alternative for computer sharing is to drill holes and run network cabling, or use "Phone Line Networking" which is, of course, only usable where there is a phone jack.

Similarly, sophisticated cordless phones have become very popular and relatively inexpensive. The majority of the newest, longest-range phones operate in the same 2.4 GHz spectrum as WLANs. Judging by the number of models displayed at stores such as Target, cordless phones appear to be outselling more conventional "wired" phones.

Interference with WLANs and 2.4 GHz cordless phones arise occasionally when microwave ovens are used near cordless phones. Microwave ovens also emit radio frequency energy within the 2.4 GHz band. However, microwave ovens adhere to strict emission limits (for the most part, the RF energy is confined to the inside of the microwave oven; if it wasn't the high-powered microwave signals could cause eye damage). Microwave ovens also operate sporadically - rarely for more than a few minutes at a time. RF lighting devices, on the other hand, will likely be turned on continuously, where their energy savings would be the highest, resulting in continuous interference.

How We Got To This Point

The genesis of the microwave oven occurred during the development of RADAR (Radio Detection And Ranging) during World War II. During the development of RADAR, it was noted that high-powered microwave emissions for RADAR systems in development caused water molecules to vibrate rapidly - resulting in heating with no external heat applied. Further experimentation showed that microwaves energy could actually cook food (and, if care was not taken, human tissue).

In order for Raytheon to develop the first industrial microwave oven, it needed a swath of spectrum to be designated specifically for use by microwave ovens. It wouldn't do to have a microwave oven on an Air Force base interfering with the base's RADAR systems. For this, and other microwave energy uses such as industrial plywood dryers and medical diathermy, the FCC created the Industrial, Scientific, and Medical (ISM) bands, the most popular of which is the 2.4 GHz band.

A considerable time after the development of the microwave oven, in response to the computer industry, the FCC permitted an additional use for the ISM bands - wireless Local Area Networks. Rules were crafted that communications devices had to "accept" interference, and "could not cause interference to existing communications systems". For equipment that was built to use the ISM spectrum and adhered scrupulously to the appropriate rules, purchasers of such systems were not required to obtain a license from the FCC to operate them.

The FCC's rules proved to be sufficiently flexible and the technology was developed to insure reasonably reliable operation of communications devices even in the presence of interference. Most importantly, there was considerable demand for Wireless LANs and later more sophisticated cordless telephones… and a near infinite number of wireless systems such as wireless video cameras, wireless stereo speakers, baby monitors, etc.

Though there were occasionally interference issues, the "high powered" use of 2.4 GHz and the "communications" use of 2.4 GHz proved to be mostly compatible. RF lighting, if widely deployed, threatens to upset this delicate balance.

The Big (Potential) Interference Issue Surfaces

This potential conflict of uses of 2.4 GHz first came to light in 1999 in concerns raised by vendors of Wireless LANs filing position papers with the FCC. More recently, the RF lighting potential interference issue surfaced in an August 6, 2001 article in the Wall Street Journal titled "Energy-Saving Light-Bulb Maker Battles With Satellite-Radio Firms For Bandwidth". The article dealt with the concerns of two companies that (then) planned to offer satellite-based broadcast radio - Sirius Satellite Radio, Inc. and XM Satellite Radio (which is now in limited operation). At issue was the amount of interference that Fusion Lighting, Inc.'s proposed new RF lighting devices would cause to the satellite radio broadcasts at 2.32 - 2.345 GHz, which are considerably removed from the spectrum where Fusion's devices operate - the 2.4 GHz band. The satellite radio broadcasters have concluded that Fusion's devices, as proposed, will cause substantial interference to their transmissions.

Left unmentioned in the WSJ article, and only now beginning to be noted by many users of the 2.4 GHz band is that if the Fusion devices are capable of causing such trouble for satellite radio broadcasting… what would the effect be to communications users of the 2.4 GHz band? Likely devastating- RF lighting devices could become as widely deployed as…light bulbs…with each one a source of interference in the 2.4 GHz band.

The potential interference issue is not just limited to individual offices or apartments. High profile (and highly profitable tenants) may well consider the use of wireless technology essential to their use of leased space. One example is Starbucks, which offers Internet access via Wireless LANs at many of their company-operated locations. Such "Public Wireless Access Points" are becoming ubiquitous, and some analysts project that PWAPs, deployed in public spaces such as airports, hotels, and many other locations may well displace the role envisioned for mobile telephone "3G" wireless data services.

What To Do

Currently, RF lighting devices are not approved for general use, so the problem is only a potential one at present. But looking ahead, it seems likely that RF lighting will be approved in some form - the potential power savings alone could justify the initially high prices for RF lighting devices.

Even if building management chooses not to install RF lighting, interference could still be an issue if tenants install RF lighting…which could then interfere with another tenant's WLAN or cordless phone. It's a somewhat humorous, but potentially very real possibility that building management would be called on to resolve a radio frequency interference complaint between tenants.

One solution… or salvation… is that in the next few years, WLAN systems will likely begin to migrate higher in the spectrum to 5 GHz, where there is much more spectrum available (and WLAN speeds will be higher). Currently 5 GHz WLAN equipment is expensive, but intense competition is beginning, and 5 GHz WLAN equipment will likely be considered affordable within two years.

Cordless phones are also likely migrating to 5 GHz spectrum along with WLANs. Likely the cordless phone migration will be slower due to greater cost-sensitivity by cordless phone buyers and range issues (though technology to enable greater 5 GHz range is evolving rapidly).

Of necessity, building managers increasingly need to become familiar with wireless technology that will be used inside their buildings. Just as "bad cellular telephone coverage" can become an issue with tenants, WLAN and cordless phone interference could also become an issue with tenants and potential tenants. It's possible that future tenant leases will include disclaimers like "This building makes use of RF lighting systems, and may render the use of devices such as Wireless Local Area Networks and cordless phones inoperable." To many building managers, the inclusion of such language may sound laughable… but it wasn't that long ago that cigarette smoking was considered an inalienable right, and any suggestion that smoking wasn't permitted in one's office or apartment would have been considered equally laughable.

About the Author

Steve Stroh is an Independent Technology Writer based in the Redmond, Washington area. Steve is Editor of Focus On Broadband Wireless Internet Access, and has specialized in writing about Broadband Wireless Internet Access since 1997. More information about Focus can be found at http://www.strohpub.com/focus.htm. Steve can be contacted via email at steve@strohpub.com with questions or comments.