STANDARDS:5.9GHz? US ETC Likely To Stay at 915MHz for Now

If there is any serious movement to using the higher frequency it isn’t coming from tolling. As Dick Schnacke of Amtech said in a ‘Vendor Perspective’ at a 5.9GHz Stakeholder Workshop organized by ITS America late December the present 915MHz works fine, has good range, and is cheap to make. Reproducing the existing functionality of 915Mhz tags in 5.9GHz would be between twice and three times the cost ($60 to $100), while ‘do-it-all’ high-end tags would be five times the cost ($150 to $200). The physics favor 915MHz in almost all respects, he points out. Bad weather and simple atmospheric attenuation are less at 915MHz. And at 5.8/5.9GHz antennas have to be close to the RF source, whereas at 915Mhz they can be 50m or more away.

At the higher frequency RF components almost have to be located up with the antenna over the lane, so: “Maintenance requires either very large, strong man-rated antenna structures, or lane closure and a man-lift.”

Serious fading occurs at the higher frequencies, so messages have to be re-sent more often or higher power levels used. In theory 5.8/5.9Ghz is seven times worse then 915MHz, but apparently because of heroic efforts of engineering it is empirically only 3 to 4 times worse, Schnacke said.

The pressure to go to the higher frequency has always been from those who cry “interference” since ETC shares the 915MHz band with a bunch of other unregulated applications. But, Schnacke says, with 915MHz usage of ET there is presently “no unworkable interference problem – and none expected that we can’t deal with through moving channels or adjusting power.” And in a worst case scenario of interference the vendors would deploy filers and improve sensitivity of antennas, which he says is “much cheaper than developing 5.9Ghz solutions.”

Physics, cost, and migration, all those issues favor sticking with 915Mhz.

So why the discussion about 5.9GHz?

It’s partly a use it or lose it issue. The FCC has allocated the spectrum. If ITS won’t use it, someone else will claim it, and it could be lost. Other arguments the ITSA group advanced include the need for new applications with more bandwidth and higher data rates.

Schnacke himself gets enthusiastic about 5.9GHz when it comes to a variety of other ITS or ‘telematics’ services, especially various vehicle control and safety services in development.

“It MUST be 5.9GHz,” he says on an overhead.

Apart from tolls, the following are available now: parking payment, access control, engine diagnostic downloads, priority at traffic signals, truck weigh station bypass, border crossing pre-clearance, fuel sales. Sounds impressive as a list like that, but when the extent of actual implementation of each of these is examined it is quite UNimpressive. While virtually all major toll facilities and quite a few smaller ones either have implemented, or are committed to implementation of electronic tolling, and electronic tolling has become a mainstream payment mode, the proportion of traffic signals with priority or border crossings with electronic pre-clearance are negligible. A recent GAO report on border crossing problems skipped over the much-hyped electronic pre-clearance as insignificant ‘experiments’ with little bearing on real problems.

Such demonstrations, or gestures of applications, are no basis on which to build a new DSRC technology.

Still, within three years there is promise of vehicle-to-vehicle communcations, data off a vehicle databus, realtime traveler information (on incidents etc) container monitoring, and in-vehicle safety warnings (of a train approaching a grade crossing for example.) Beyond that there could be cooperative driving with vehicles set to detect a dangerous closing rate on the car ahead or some other obstacle, collision warning at intersections and even lane keeping. Some no doubt will be implemented, but it is unclear which, and the enthusiasts for ITS sometimes sound as if they are keen to get ET into the higher frequency, not for any benefit to tolling, but perhaps because they see it as underwriting the economic viability of the other applications

Bruce Abernathy of BWR (TRAFFIC TECHNOLOGY INTERNATIONAL Feb/MAR 00 P62) says the ITS world has been upstaged by the broader electronics industry. He’s right about that. The broader industry of telecom, oil companies, and car and appliance manufacturers has the power of mass production which drives down costs and dictates what is economic and what isn’t.

915MHz is decried for the problem of ‘interference’ but the flipside of interference is what is generating that interference! That is the plethora of wireless devices (mostly cordless and analog cell phones) with components manufactured and traded on a vast scale and at low prices - the low cost of those components is the reason US ET transponders can be sold for $25, whereas the 5.8Ghz gear - out there lonely and interference-free in the higher frequencies - costs a multiple of that price. 5.8/5.9GHz uses custom parts.

Abernathy contrasts the ITS world and its 10 year effort to achieve only partial DSRC standards with the group of telephone, chip, and computer makers which managed in 18 months to establish the Bluetooth wireless networking standard. Bluetooth sensibly uses 2.4Ghz - near the frequency used by digital wireless phones - to be practical and economical to implement. He suggests that Bluetooth be adopted as the universal standard for vehicle-roadside communications including electronic tolling.

In that detail he appears to be stretching things.

Abernathy says that Bluetooth will operate at distances to the 100m needed for vehicle-to-roadside coms at highway speed. Intel’s rep on the Bluetooth panel told us it is designed to work at a maximum range of 10m, not 100m, and in a stationary mode! Car companies might use Bluetooth to eliminate the mass of wires between appliances within the confines of one vehicle, the Intel expert told us, and similarly in a truck between the tractor and the trailer. No way, would it be suitable for vehicle-roadside applications, he said.

Rich Weiland, ITS expert in Chicago who is chair of the 5.9GHz group for ITSA, says the Automobile Manufacturers Internet Collaboration (AMIC) group, which represents the major carmakers, sees the possibility of using wireless datalinks at gas stations to order up fuel, operate robotic fueling devices, and allow the motorist to download digital music and videos (hopefully only for the passengers). But not with Bluetooth, he says.

AMIC, Weiland says, thinks Bluetooth is inadequate for such data-heavy applications as the download of movies. And, he says, AMIC, at a recent meeting, adamantly ruled out the idea of using Bluetooth for any off-board (vehicle-to-roadside) communications. They want to keep Bluetooth strictly for a range of a few meters and between stationary devices, as a kind of wireless personal network at home or as a vehicle systems net within a single vehicle. It is too slow to initialize for vehicle-roadside, too.

The notion of there being some neat overall standard for vehicular radio coms, that ITSA or FHWA can dictate, is probably wishful thinking.

Already some of the most successful ITS applications - GM’s OnStar and Ford’s Rescu - make use of cellular telephone plus GPS, completely bypassing DSRC.

At the 5.9GHz Stakeholders workshop a rep of Mack Truck said his company had abandoned the idea of folding fleet management and service coms (such as download of engine data, fuel and other driver purchase authorizations, and waybill details) into a 915MHz transponder because of the lack of a standard there. So much for the Hughes/Raytheon tags built to ASTMv6 or the so-called sandwich standard. Mack Truck will be announcing a wireless databus this year. Guy Rini of Mack provides the teaser that it won’t be either 915MHz or 5.9GHz.

A guess is that it will be a wireless local area network at 2.4GHz to an established IEEE-802.11 standard, which unlike Bluetooth, has been successfully tested and deployed at “medium” highway speeds for vehicle-roadside coms. Mack’s application will be used at truck-stops and truck-yards where trucks are either crawling along at 10mph going in a driveway or gate, or even when they have come to a stop. A few transit buses use IEEE-802.11 2.4GHz successfully for wireless data transfers in depots in an application sometimes termed wireless ethernet.

For trucking and bus operations it may be goldplating to go for the ITSA/FHWA ideal of a new system that supports 100mph operations in a part of the spectrum with little componentry mass-produced, when 30mph is quite adequate and the manufacturers can tap cheap parts and established hardware and software packages.

At the same time Texas Instruments is developing a market for a couple of specialized transponders:

(1) keyfob transponders that now routinely come with new cars: 134KHz, 4m range

(2) 134KHz/903MHz (down/uplink) transponders tradenamed Speedpass, mounted on the car’s back window for vehicle-gaspump coms, 1m, mostly Mobil ‘Speedpass.’ Texaco and Shell through a joint subsidiary Equiva are working on a whole integrated vehicle-gas station com system that could involve a robotic gas pump, engine diagnostics and download of in-vehicle entertainment. It has not yet chosen an RF technology, but will soon. Bluetooth, or an 802.11 LAN at 2.4GHz? The 5.9GHz is struggling to gain applications.

A Belgium company SmartMove, an IMEC associate, has a Boston-based US sub which has been working with Caltrans and has demonstrated a network operating at 5.9GHz that apprently supports a heap of applications via Java modules. It has designed a chip and frequency multiplexing system that supports 24Mbits/sec compared to 1Mbit/sec data rate of most existing wireless systems. Bart Stevens, who despite the name speaks with a good Flemmish accent, pitches the idea that such broadband “data pumps” are the way of the future, that a single transponder per car or truck is what is needed. He says the existing vendors are short-sighted in sticking with their relatively low data rate systems.

Maybe, maybe not.

Stevens readily agrees that tolling does not need broadband and that other applications will have to support it. It isn’t clear to us what those other applications will be. Many technically promising safety applications are hampered by uncertainty over legal liability issues, and questions about how much people will pay for them. For example, how much traveler information service are people going to pay for? In-vehicle navigation, while a technical marvel, seems to have attracted only a small niche market of customers. And how much entertainment do people in back seats of cars really need to get via a wireless net? They may be more inclined to buy it at home, via cable and satellite and stick it in the car on a DVD player when they want it there. The gas station systems will have plenty of competition.

The ITS databus or IDB is another integration project that is attempting to rationalize vehicular communications and transactions by forming a common interface between vehicular systems and communications with the world outside. It plans a demonstration in 2002. Good luck. They’ll need it. Planning is tough in the hurly burly of hightech innovation.

(Contacts Rich Weiland 847 699 7800, Dick Schnacke Amtech/Intermech 972 733 6623, Bruce Abernethy BWR 214 770 1300, Bart Stevens SmartMove 617 252 3700, IDB arlan.stehney@idbforum.org)