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Mapping From Wi-Fi "Fingerprints" Could Improve Indoor Navigation

Korean researchers build maps from Wi-Fi signals collected by mobile devices, even if GPS signals are lacking

2 min read
Mapping From Wi-Fi "Fingerprints" Could Improve Indoor Navigation

With outdoor mapping tools widely available and generally successful (Apple’s recent mapping debacle being the exception that proves the rule), technologists are pushing forward the state-of-the-art in indoor navigation, likely to be a hot area for advances throughout 2013.

This week, KAIST, The Korea Advanced Institute of Science and Technology, announced a development that definitely is a step, so to speak, in the right direction: a new method to build a map from Wi-Fi radio signals without accompanying GPS tags or manual inputs of map coordinates. Most current systems need GPS signals to fully interpret the data coming from Wi-Fi routers.

Dong-Soo Han, a professor in KAIST’s Department of Computer Science, and his research team used software embedded in smartphone apps to upload a Wi-Fi fingerprint, that is, information about the current set of Wi-Fi signals and signal strengths available to the mobile device at that moment. Users were asked to input their home and office addresses. The mapping system developed linked the geographic coordinates of those locations to the Wi-Fi fingerprints most frequently collected by the smartphones, combining that information with those from other users to create an overall Wi-Fi radio map of a selected geographic area. Such maps could be used as the basis of indoor navigation or indoor location-based services (that, for example, send a coupon when you pass a particular restaurant in a shopping mall). Han’s team tested the system in four areas of Korea with mixed residential and commercial locations.

In a press release, Han is quoted as saying, "Although there seem to be many issues like privacy protection that have to be cleared up before commercializing this technology, there is no doubt that we will face a greater demand for indoor positioning system in the near future."

Mike Stanley, a systems engineer at Freescale Semiconductor, told Spectrum that “Using measured Wi-Fi signal strengths to develop Wi-Fi fingerprints is an area that has been receiving attention from researchers, and is certainly a valid approach for indoor environments."

Stanley grimly questioned, however, one possible use of Wi-Fi mapping information envisioned by the researchers, that is, for emergency rescue operations. It could be difficult, he pointed out, to find victims under piles of rubble using Wi-Fi fingerprints when the rubble “may very well contain the remains of the Wi-Fi base stations upon which they based their fingerprint analysis.”

Image: ST Microelectronics

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Metamaterials Could Solve One of 6G’s Big Problems

There’s plenty of bandwidth available if we use reconfigurable intelligent surfaces

12 min read
An illustration depicting cellphone users at street level in a city, with wireless signals reaching them via reflecting surfaces.

Ground level in a typical urban canyon, shielded by tall buildings, will be inaccessible to some 6G frequencies. Deft placement of reconfigurable intelligent surfaces [yellow] will enable the signals to pervade these areas.

Chris Philpot

For all the tumultuous revolution in wireless technology over the past several decades, there have been a couple of constants. One is the overcrowding of radio bands, and the other is the move to escape that congestion by exploiting higher and higher frequencies. And today, as engineers roll out 5G and plan for 6G wireless, they find themselves at a crossroads: After years of designing superefficient transmitters and receivers, and of compensating for the signal losses at the end points of a radio channel, they’re beginning to realize that they are approaching the practical limits of transmitter and receiver efficiency. From now on, to get high performance as we go to higher frequencies, we will need to engineer the wireless channel itself. But how can we possibly engineer and control a wireless environment, which is determined by a host of factors, many of them random and therefore unpredictable?

Perhaps the most promising solution, right now, is to use reconfigurable intelligent surfaces. These are planar structures typically ranging in size from about 100 square centimeters to about 5 square meters or more, depending on the frequency and other factors. These surfaces use advanced substances called metamaterials to reflect and refract electromagnetic waves. Thin two-dimensional metamaterials, known as metasurfaces, can be designed to sense the local electromagnetic environment and tune the wave’s key properties, such as its amplitude, phase, and polarization, as the wave is reflected or refracted by the surface. So as the waves fall on such a surface, it can alter the incident waves’ direction so as to strengthen the channel. In fact, these metasurfaces can be programmed to make these changes dynamically, reconfiguring the signal in real time in response to changes in the wireless channel. Think of reconfigurable intelligent surfaces as the next evolution of the repeater concept.

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