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When Searching Goes Astray

Summaries of Research and Inventions from Science and Technology Journals

3 min read

Have you ever wondered whether search engines pay attention when you spice up your searches with Boolean operators, such as AND, OR, MUST APPEAR (+), PHRASE (""), and NOT? Well, apparently they don't--or at least they don't return much better results when you use them. Two researchers from the University of South Carolina and Pennsylvania State University investigated the effect that these operators had on the total number of documents retrieved, the number of relevant documents, and document ranking on Google, AOL, and MSN. They found that most of the operators had little positive effect. And that could be why only about 10 percent of searches bother with them. Don't, however, completely give up on your Boolean buddies. The researchers did find that the OR operator, as expected , was able to noticeably increase the number of hits on Google but not on the others and that using the PHRASE operator resulted in more relevant hits in general. Surprisingly, using the AND operator, which should narrow a search, actually increased the number of results returned by MSN.

Coverage, Relevance, and Ranking: The Impact of Query Operators on Web Search Engine Results , by C. M. Eastman and B. J. Jansen, ACM Transactions on Information Systems , October 2003, pp. 383--411.

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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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