Echo cancellation

Echo cancellation

Over the past few decades there has been a remarkable shift in the methods through which people communicate. Whether conducting business or checking in with family, wireless devices have changed the standard of communication all over the world. Along with this growing reliance on wireless communication, the demand for high quality transmission has grown. Customers have come to expect a clear, strong signal with little to no delay.

One of the biggest complaints service providers hear has to do with the presence of an echo. Anyone who’s called into a teleconference, used a hands free device while driving, or spoken on a mobile phone has experienced the annoyance of an acoustic echo. This occurs when a microphone picks up audio signals from the speaker’s voice and routes it back to them on a slight delay, giving the effect of an echo.

Echo cancellation is methodology put in place by network providers to reduce the instances of acoustic echo. Integrated into voice switches or directly within handheld devices, echo cancellers use algorithms that work as adaptive filters, preventing a person’s speech from being transported back to them.

How full duplex functionality is changing the game

Today, wireless carriers are limited to two technologies with regard to transmission:

  • frequency division duplex (FDD), in which one frequency is used to send and one to receive
  • time division duplex (TDD), in which messages are sent and received at different times

With the development of full duplex radio integrated circuits, Saffron Communications has successfully removed the need for dual frequencies or separately timed signals. By eliminating the use of the FDD or TDD method of transmission, this industry-changing technology enables voice and data to be sent and received at the same frequency and same time, resulting in an increase in signal speed and a reduction of the total bandwidth required for high quality transmission.

Echo cancellation within the parameters of full duplex

Working to cancel echo during simultaneous transmission was one of the most challenging parts of the process for Dr. Krishnaswamy and the team at Columbia University. In theory, an integrated circuit using the same frequency both send and receive signals at the same time and would be overwhelmed by “self interference.” The tiny scale of the integrated circuit with which they were working added an extra level of complexity to the undertaking. The solution was to engineer a way to cancel the local transmitter’s signal in the local receiver circuitry, thus allowing the remote signal to be heard. And, full duplex functionality with echo cancellation was achieved.