First True Full Duplex Wireless Radio Communication


You might be surprised by that technology till date couldn’t actually create a device that could Transmit and receive at the same time wirelessly – aka Full Duplex communication. You might argue that your GSM/CDMA phone, your wifi already does that. But if you jump into the details of how these wireless networks operate, you will realize they use Time division multiplexing or a similar technique to make it simulate a full duplex communication. TDM divides the time into slots (of the order of ms) which are used for Transmit and followed by Receive, both in separate slots, i.e. at a different time. Because these time slots are as large as 2-10 milliseconds, they feel to be happening at the same time.

Radio traffic can flow in only one direction at a time on a specific frequency, hence the frequent use of “over” by pilots and air traffic controllers, walkie-talkie users and emergency personnel as they take turns speaking.

Stanford‘s engineering labs have discovered new ways of avoiding wireless interference, and hence make it to possible to have full duplex communication even in a noisy environment.  Electrical engineering graduate students, Jung Il Choi, Mayank Jain and Kannan Srinivasan, began working on a new approach when they came up with a seemingly simple idea. What if radios could do the same thing our brains do when we listen and talk simultaneously.

A newfangled wireless technology developed is proving that signals can indeed be sent and received at the same time. Typical wireless signals have to take turns when it comes to listening and transmitting. As an example, it’s impossible for a WiFi router to “shout” out signals while also being intelligent enough to quiet its own voice in order to hear “whispers” from a connected device.

Their main roadblock to two-way simultaneous conversation was this: Incoming signals are overwhelmed by the radio’s own transmissions, making it impossible to talk and listen at the same time.

The breakthrough came when researchers found that radios could be tweaked to filter out the signal from its own transmitter. This phenomena has been derived from noise-canceling headphones, which cancel out the sound waves from surroundings.

“When a radio is transmitting, its own transmission is millions, billions of times stronger than anything else it might hear [from another radio],” Levis said. “It’s trying to hear a whisper while you yourself are shouting.”

If a radio receiver could filter out the signal from its own transmitter, weak incoming signals could be heard. “You can make it so you don’t hear your own shout and you can hear someone else’s whisper,” Levis said.

This technology can help overcome various current challenges like overcoming a major problem with air traffic control communications. With current systems, if two aircraft try to call the control tower at the same time on the same frequency, neither will get through. Levis says these blocked transmissions have caused aircraft collisions, which the new system would help prevent.

If this can be packaged into a commercially viable platform, it could instantly double the amount of information sent over existing networks, and on an even grander scale, it could allow airplanes to radio into control towers simultaneously.

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