Want To Give Your In-Store Cell Reception A Huge, Cheap Boost? Use The AC Ducts

Written by Evan Schuman
September 15th, 2010

As retailers get more creative about ways to lure mobile-phone-lugging shoppers into their stores, they have to deal with the fact that the buildings they use were never designed to allow outside signals to mix with the customers and the display cases. A research team at North Carolina State University has come up with an unorthodox tactic that may help retailers pull in outside cellular tower signals for shoppers, boost Wi-Fi signals and extend the range for RFID: air-conditioning ducts.

It seems that those ducts—officially dubbed heating, ventilating and air-conditioning (HVAC) ducts—snaking through these old multi-level escalator-using buildings are natural signal boosters. “The HVAC ductwork is an excellent conduit for the radio transmissions because the ducts typically consist of hollow metal pipes,” the university’s report said. “Those pipes can be used to guide the radio waves, keeping the waves from dispersing, and helping to maintain a strong signal over a greater distance.”

The study was originally conducted to study RFID signals and the ducts can certainly be used for that purpose, but many retailers today consider the cell tower signal problem more challenging. Sam’s Club, for example, had to offer its customers Wi-Fi partially because they often couldn’t use mobile devices any other way, which would have put a crimp in the mobile plans of the Wal-Mart-owned warehouse club. Other chains have struggled with metal roofs that never considered cell signals during construction.

“In some buildings, this could be a very elegant solution,” said Dan Stancil, co-author of the study paper, professor and head of NC State’s Department of Electrical and Computer Engineering.

Although the stores would still need a microcell repeater to grab and strengthen the signal, the ducts don’t merely serve as a convenient, hidden place to house equipment. “You’re using the duct itself as a distributed antennae,” Stancil said.

When used for Wi-Fi or RFID location-tracking (regardless of whether it’s pallets, store associates, item-level products or customer mobile devices being tracked), Stancil stressed that engineers and installers will have to significantly recalculate where transmitters are placed. That’s because the ducts create lines of sight that are very different than a straight line so “the signal delays will not be as expected. This wouldn’t be the shortest path,” he said, but it may be the path with the smallest amount of signal loss.

“The ducts will increase the range in a very different way, meaning that you can cover Wi-Fi with far fewer access points,” Stancil said.


One Comment | Read Want To Give Your In-Store Cell Reception A Huge, Cheap Boost? Use The AC Ducts

  1. Terry Hare Says:

    HVAC ductwork sound like a great oportunity, but don’t jump in just yet.
    NATIONAL FIRE CODE requires plenum ratings for equipment installed in the building air plenum.
    Active equipment would have to be seperated from the plenum by a rated enclosure and the antenna or waveguide port would have to be plenum rated.
    That means no plastic or fiberglass antennas. Consider a waveguide port connection at the end of the duct or an all metal antenna.
    This trick will only work in buildings that have all metal ducts.
    Also note that the system should be shut down for HVAC maintenance to protect personnel from RF.
    I would consider all the risks of trying something like this versus the cost of traditional repeaters that are already listed and give more even coverage.


StorefrontBacktalk delivers the latest retail technology news & analysis. Join more than 60,000 retail IT leaders who subscribe to our free weekly email. Sign up today!

Most Recent Comments

Why Did Gonzales Hackers Like European Cards So Much Better?

I am still unclear about the core point here-- why higher value of European cards. Supply and demand, yes, makes sense. But the fact that the cards were chip and pin (EMV) should make them less valuable because that demonstrably reduces the ability to use them fraudulently. Did the author mean that the chip and pin cards could be used in a country where EMV is not implemented--the US--and this mis-match make it easier to us them since the issuing banks may not have as robust anti-fraud controls as non-EMV banks because they assumed EMV would do the fraud prevention for them Read more...
Two possible reasons that I can think of and have seen in the past - 1) Cards issued by European banks when used online cross border don't usually support AVS checks. So, when a European card is used with a billing address that's in the US, an ecom merchant wouldn't necessarily know that the shipping zip code doesn't match the billing code. 2) Also, in offline chip countries the card determines whether or not a transaction is approved, not the issuer. In my experience, European issuers haven't developed the same checks on authorization requests as US issuers. So, these cards might be more valuable because they are more likely to get approved. Read more...
A smart card slot in terminals doesn't mean there is a reader or that the reader is activated. Then, activated reader or not, the U.S. processors don't have apps certified or ready to load into those terminals to accept and process smart card transactions just yet. Don't get your card(t) before the terminal (horse). Read more...
The marketplace does speak. More fraud capacity translates to higher value for the stolen data. Because nearly 100% of all US transactions are authorized online in real time, we have less fraud regardless of whether the card is Magstripe only or chip and PIn. Hence, $10 prices for US cards vs $25 for the European counterparts. Read more...
@David True. The European cards have both an EMV chip AND a mag stripe. Europeans may generally use the chip for their transactions, but the insecure stripe remains vulnerable to skimming, whether it be from a false front on an ATM or a dishonest waiter with a handheld skimmer. If their stripe is skimmed, the track data can still be cloned and used fraudulently in the United States. If European banks only detect fraud from 9-5 GMT, that might explain why American criminals prefer them over American bank issued cards, who have fraud detection in place 24x7. Read more...

Our apologies. Due to legal and security copyright issues, we can't facilitate the printing of Premium Content. If you absolutely need a hard copy, please contact customer service.