Researchers from South Korea’s Electronics and Telecommunications Research Institute demoed a new wireless technology this week that could enable better device-to-device (D2D) communications, allowing smart gadgets such as phones to link to one another without going through a base station. Many researchers believe that D2D capability will be a key feature in the next generation of wireless networks after 4G LTE and LTE-Advanced. It could help decongest overloaded base stations and usher in new applications, such as screening a video clip on a big screen while it's actually stored on your phone, or downloading the service manual directly from your smart car.
Now, I know what you’re thinking: Don’t D2D technologies already exist? Sure they do. You may be scrolling through this story using a Bluetooth-connected mouse. Perhaps you bought a cup of coffee this morning by tapping your smartphone to a near field communication (NFC)-enabled cash register. Other D2D standards already available or in the works include Wi-Fi Direct, LTE Direct, and Peer Awareness Communications.
But these technologies have yet to catch on in a big way. And maybe for good reason. Surveys show that users don’t particularly like touching their phones to things or scanning a list of available devices to connect with the one they want, which Wi-Fi Direct and most other D2D technologies require. Most people find all that tapping, scrolling, and clicking to be physically demanding, annoying, or just plain awkward. Given the choice, we would much rather engage with smart objects simply by pointing our smartphones or tablets at them—or better yet, by looking at them, such as with smart glasses.
But here’s the problem: In order to connect with, say, a smart poster or with your friend’s television, your phone must know its ID, such as an IP address or a given nickname. Without knowing this information or making you select it from a list, how would your phone identify the device you’re pointing it at?
The South Korean team, led by Young-Hoon Kim, devised a solution using a novel beamforming technique. Dubbed “Look And Link,” it uses an array of antennas to direct a phone’s transmissions toward the correct receiving device. The demo took place on Wednesday at an IEEE wireless standards meeting in Los Angeles.
So how does Look And Link work? Imagine, for instance, that you are strolling down the street, and you see a restaurant that you think you might want to try. But this is the future, so rather than walk in and ask for a menu, you simply stare through your smart glasses at the smart sign in the window. Using a built-in antenna array, your smart glasses form a directional beam to transmit a query toward the smart sign, thus avoiding querying other nearby devices.
But not just any beam pattern will do the trick. Conventional techniques, for instance, would create a beamform that, while concentrating most of its gain toward the smart sign, would also radiate in unintended directions. So devices that you’re not looking at, but that are close to you, might receive a signal that’s just as strong—or stronger—than the signal received by the smart sign. In the below figure, for example, both the device you’re pointing at (Device A) and a nearby device (Device B) will receive your query quite strongly.
Kim and his team solved this problem by randomly varying the shape of the beam over short time intervals—a technique they call jittering. Only the gain in the direction of the target device stays the same. The effect is that while the smart sign receives a signal of consistently high strength, other nearby devices see huge gain changes. The researchers illustrate the concept nicely in the figures below:
So now, when your smart glasses send out a query to the smart sign, nearby devices know not to answer. Meanwhile, the smart sign transmits back its ID, allowing your glasses to connect with it using some other wireless standard, such as LTE Direct. Then you can download information from the sign, such as menus and operating hours. Maybe you even decide to make a reservation for later that evening.
Kim points out that another advantage of Look And Link, besides enabling device identification through pointing, is that it allows devices to link with one another quickly. Using Look And Link, he says, two devices can connect in a just a few seconds, compared to almost a minute using Bluetooth.
At Wednesday’s demo, the researchers used a prototype transmitter with four antennas, according to Byung-Jae Kwak, one of the team members. He concedes that four or more antennas may not fit into today’s smartphones, which currently have no more than two. But, he says, cellular carriers as well as unlicensed device makers are beginning to look toward higher frequencies, which require smaller antennas. The South Korean team demoed Look And Link, for instance, using 5 GHz spectrum. “We are also interested in using 60 GHz,” Kwak said in an e-mail. “In that case, we can easily put eight antennas in the space of a finger nail.”