Wiretapping Woes

Trouble ahead for those wanting to monitor Internet-based calls

4 min read

The telecommunications world was a much simpler place in 1994, when the U.S. Congress passed a landmark wiretapping law. At the time, the statute was meant to take advantage of the new fact that instead of doing wiretaps the old-fashioned way--by walking into a local phone company office with a warrant and some alligator clips--law enforcement officers now could conduct a wiretap centrally on a carrier's network by duplicating a phone call digitally and directing the copy to police headquarters.

Starting on 14 May, the 1994 law, the Communications Assistance for Law Enforcement Act (CALEA), will also apply to some voice over Internet Protocol providers, and the U.S. Federal Bureau of Investigation has asked that it eventually be extended to all Internet-based communications. The wiretapping statute was originally designed for traditional telephone companies, which use circuit switching to create a dedicated channel for each phone call. But today, using Internet telephony, almost anyone can be a telecommunications carrier, including Google, Skype, Vonage, and Yahoo, to name just four companies that didn't exist in 1994.

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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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