Bandwidth Allocation Hits the Road
While wireless carriers have spent the last several years fighting for spectrum licenses for cell phone networks, WLANs have been relegated to unlicensed radio bands. But thats about to change with the introduction of a band set aside for automotive and other outdoor applications.
The Federal Communications Commission has been hurrying the allocation of 75MHz of spectrum on the band that spans 5.85GHz to 5.925GHz, to be used specifically for DSRC (dedicated short-range communications), the short-range wireless communications that focus on roadside safety. FCC officials said the commission is focusing on the band now more than ever because transportation safety is a national priority.
Companies that plan to sell products that run on the band said the applications will go beyond that.
"There are a lot of very important public safety applications, but people arent going to buy this technology just for public safety," said Sheung Li, product line manager for home networks at high-speed wireless LAN radio manufacturer Atheros Inc., in Sunnyvale, Calif., adding that the industry is already looking at how to take advantage of the band for corporate use.
"It makes sense for the trucking industry. Often, when truckers stop by truck stops, they do a full data dump. ... They could do this at public access points. Likewise, this is envisioned for use by trains as they go by various checkpoints," Li said.
Other applications include electronic toll taking, collision avoidance systems, systems that let transportation dispatchers track employees every time they pass checkpoints, systems that warn drivers of nearby emergency vehicles, and the ability to download maps and directions from kiosks at service stations.
Certainly, the ability to collect tolls wirelessly, to warn one vehicle of anothers approach and other automotive technologies exist today, but there is no single standard.
"At this point, all these technologies exist in one form or another, but theyre proprietarynone of them intercommunicate," Li said. "If someone were to take advantage of all these services, they would need five or six separate radios."
Atheros is involved in the adoption of technology for the new band largely because a DSRC standards writing body, comprising WLAN and automotive companies, voted 802.11a the technology of choice to run on the band. 802.11a is the high-speed, wireless Ethernet technology on which Atheros develops radios for myriad hardware companies. 802.11a was previously relegated to the unlicensed 5GHz range. The DSRC efforts open up the WLAN industry to a new set of applications on a licensed band, which guarantees less interference from other systems running on the band. The FCCs Notice of Proposed Rule Making requested comment on the spectrum-sharing potential of DSRC operations in the band, but, generally, operations in a licensed band are more protected than those in an unlicensed band.
"It essentially opens up another band for OFDM [orthogonal division frequency multiplexing, on which 802.11a is based]," said Jim Lansford, vice president of business development at Mobilian Corp., which develops wireless radios that support multiple wireless protocols and, therefore, keeps track of which protocols are hot. "This band is supposed to be used for telematics, but that doesnt mean you couldnt use it in the garage or your home. Its supposed to allow for any car-to-infrastructure communication."
Lansford said, though, that a market based on DSRC is a nascent one. "[The choice of 802.11a] was a moral victory," he said. "Its not entirely clear yet what the market is for people to be shipping [WLAN] data from the car."
Atheros officials, though, said they are already making deals with automotive electronics companies to develop systems both inside and outside the car and that because 802.11a can run in the 5GHz band, its possible systems will be available for that band even before the FCC officially approves the 5.9GHz band.
Li said he expects DSRC technology to start appearing in products about a year from now; automotive companies have tentatively committed, he said, but the lead time is long for anything that has to be built into a car. He declined to say which automotive companies have agreed to support the technology.
"The fact that the [802.11a] technology already works means that they can also do this in the unlicensed band," Li said. "The notion is that they wouldnt put this in a vehicle until the band is allocated," he said, but added that companies could start building systems outside the car because they will be compatible with systems inside the car when they are eventually installed.
It is not clear, either, when the new band will be officially designated for the 802.11a-based automotive systems because it generally takes many months for rules to make it through the FCC. Currently, the proposed rule is out for public comment, along with hundreds of other rules.
"For each FCC decision, about 10 percent are appealed," said an FCC lawyer who asked not to be named. "There are about 300 votes a year for each commissioner."