GROUND BREAKING MOBILE TECHNOLOGY. SINGLE FULL DUPLEX CHIP HAS BEEN DEVELOPED

Image: Negar Reiskarimian/Columbia Engineering

A ground breaking technological advancement in mobile telephony has been achieved by researchers in the university of Columbia; a single chip that can receive and transmit mobile signals at the same frequency at the same time in a telephone has been successfully developed. It means that with the full functionality of this system, our mobile phones data capacity could more than double. This development could lead to serious improvements in the way our mobile telephones would function in the nearest future.

For the Newbies/Novices 

I want to give a brief explanation of communication modes before i proceed with this article so my readers would not be thrown off balance while reading.

In communication, there are two basic modes of communication viz:

1. Simplex

2. Duplex 

In a simplex mode, communication is unidirectional. Information flow goes in one direction only. A typical example is your radio or tv at home. Transmitted information cannot receive any instantaneous feedback to the source. Thanks to the internet and social media, Radio and Tv communications are somewhat half duplex these days (lesson for another day). 

In duplex systems, communication is bidirectional. The sender and the receiver can communicate freely at the same time as in a telephone conversation or one after the other (Half Duplex as in Walkie Talkie). 

How do Current Devices Work?

In today's mobile devices, the sending antenna and the receiving antenna are separate. There are at least two antenna which send and transmit information using of the following two methods:

1. Time-division Duplex

2.  Frequency-division  Duplex

  

In time division, the two antenna will take turns to transmit or receive at the same frequency. In
frequency division duplex, the two antenna may transmit and receive signals at the same time at a varying frequencies. 

The Story

The Institute of Electrical and Electronics Engineers (IEEE) reports that in 2015,  Harish Krishnaswamy who is an Electrical Engineer at Columbia University designed, developed and demonstrated the possibility of full duplex communication from two antenna which were broadcasting at the same frequency and time using a radio he built.

This feat inspired a P.HD student  named Negar Reiskarimian under the guidance of Krishnaswamy  and sponsored by the Defence Advanced Research Projects Agency (DARPA) modified and embedded this innovation into a chip such that you have the transmitter and receiver on the same antenna.  This technology when properly refined can be used in smartphones and tablets.

Compared to the traditional models, the new full duplex radio chip is more efficient. “You’re not wasting time or frequency,” Krishnaswamy says. Such conservation is especially important as smartphones use more data, and companies search for ways to free up frequencies. Krishnaswamy says his lab is already working with several chip manufacturers to refine the concept.


In the past, electrical engineers have bypassed reciprocity by designing elements called circulators built of magnetic materials. By applying a magnetic field, an engineer can disrupt reciprocity by permitting waves to flow only forward and not backward, which allows for the simultaneous transmission of two signals. These circulators are usually too bogus and expensive and have only been used by the military in extreme circumstances, not in any way fit for mobile circuits because of the magnets (assuming the system could be miniaturized).

To achieve its efficiency, the new chip had to circumvent a longstanding principle called Lorentz Reciprocity, in which electromagnetic waves are thought to move along the same paths when traveling both backward and forward.

To overcome that limitation, Reiskarimian implanted silicon transistors on the face of a CMOS chip in an arrangement that reroutes signals as they are captured by both the transmitter and the receiver in order to avoid interference. “You essentially want the signals to kind of circulate in a clockwise sense,” Krishnaswamy says.

It also helped to use an echo-cancelling receiver that the lab also pioneered. This receiver solves the classic problem that transmitted signals tend to "echo" back into a receiver when a full duplex radio is in operation. This echo can be billions of times stronger than any external signal that a receiver needs to process. The echo-cancelling receiver cuts through this noise by learning what the transmitted signal was and subtracting that out of the signal that the receiver processes.

It is worthy of note however that this new chip does not have a high enough broadcasting power level to connect to a mobile network. It’s in the neighborhood of 10 to 100 milliwatts, which is about where a Wi-Fi network typically starts, but mobile networks operate at far higher levels. There are a few ways that Krishnaswamy is already planning to try to bolster the power level, such as by rearranging the components of the chip or choosing different hardware to build it.

Big break through here SPKB blog will keep you posted on further results.