Mobile POS's Unfixable Single Point Of Failure: Wi-Fi

Just when you thought you had figured out how to deploy in-store mobile devices, something comes along to remind you that it's not that simple. Last month, the FCC ordered 20 small online retailers to stop selling illegal devices that jam the signals for mobile phones, GPS and Wi-Fi. No surprise there—but also not much impact, because such devices are easily available from other online retailers. That means anyone willing to pay as little as $80 could walk into a store in your chain and jam the Wi-Fi that your mobile POS depends on.

It's a classic single-point-of-failure problem, and it could be frighteningly disruptive—especially since this holiday season will be the first at many stores with lots of in-store mobile devices in use, and almost all retailers are using Wi-Fi to keep them connected. A saboteur who uses a pocket-size jammer wouldn't have access to payment-card information, but what's supposed to be an impressive demonstration of retail technology would just irritate customers and frustrate associates—especially during the high-volume times that mobile POS should be a relief. And that's just from an intentional saboteur. Unintentional Wi-Fi jamming could have even worse effects.

The problem is that many in-store mobile devices, including the iPod Touch, use Wi-Fi with 2.4 GHz signals. That frequency range is not exclusively for wireless networking. Cordless phones, wireless microphones and other personal radio products were made for years that used signals in the same range.

That means a saboteur or prankster isn't the only one who might walk into the store and jam the Wi-Fi. To be clear, what's illegal is to "willfully or maliciously interfere with or cause interference to any [legal] radio communications," as the FCC's order put it. It's also illegal to market devices for the purpose of creating interference. So that saboteur who turns on a jammer in the store is breaking the law.

But a shopping-mall musical performer who comes into the store and forgets to turn off her wireless mike—that's not illegal. The mike's not illegal, and neither is forgetting to turn it off. That doesn't make it any less a problem if it disrupts a customer's mobile checkout.

Small children who bring in certain radio-powered toys can be just as disruptive, even if the kids themselves are well behaved. Just as bad can be malfunctioning phones or PDAs that scatter static across the Wi-Fi band, especially if it happens in momentary bursts that are just long enough to break a Wi-Fi signal.

Even more of a potential problem is Wi-Fi equipment from other retailers—such as pop-up stores.Even more of a potential problem is Wi-Fi equipment from other retailers, especially (in an indoor mall) from holiday pop-up stores. Those stores have to be set up and torn down quickly, often on a tight budget. That means Wi-Fi is very appealing, and so is keeping non-standard or off-brand equipment around long after it should have been replaced.

That's an invitation to problems, especially for the pop-up store's neighbors. For example, some Wi-Fi access points that used early versions of the 802.11n standard worked perfectly with equipment from the same vendor but completely wiped out all other Wi-Fi communications within range of the signal, which—being 802.11n—is a much wider area than previous Wi-Fi access points covered.

Lots of that so-called "pre-N" equipment is still in use, which means a new, temporary next-door neighbor could intermittently disrupt a store's mobile POS through the whole holiday season—exactly when mobile POS is supposed to be helping the most. And ironically, even though it could subject the whole store to a much stronger signal than the low-power, short-range pocket jammer carried by a saboteur, that unintentional jamming is technically legal.

Unfortunately, there's not much that IT can do in advance when a Wi-Fi jammer moves in next door or a saboteur settles in for the afternoon. If the store is using Wi-Fi-equipped phones and there's a cell signal available, associates might switch to that—but that won't work with the iPod Touch and Wi-Fi-only iPad, the two most popular in-store mobile devices.

In some cases, a store's Wi-Fi can be switched from 2.4 GHz to the less frequently used 5 GHz band if the equipment can support either 802.11a or some versions of 802.11n. But that won't work with the iPod Touch either. (The Wi-Fi iPad can use 5 GHz—and it's nice to know you get something more than a pretty screen for all that extra money and bandwidth.)

Mostly, though, associates who have Wi-Fi problems will probably have trouble even figuring out that Wi-Fi is the problem. With new wireless networking equipment, new mobile devices that get bumped around more than expected and new back-end software that may choke under the stress of Black Friday and the days that follow, associates might not even think the problem could be anywhere but in the store's own systems.

Yes, it could—and in a certain number of cases, it probably will be. Just hope that if their Wi-Fi is jammed, it's because of a prankster who causes problems for a few minutes and then moves on. If the problem is a new neighbor, the Wi-Fi could be jammed for the rest of the year.