Boosting WiFi

CMOS circulator IC on a printed-curcuit board, interfaced with off-chip inductors. Credit: Negar Reiskarimian, Columbia Engineering

WiFi has become ubiquitous, both inside our homes and in open urban spaces. Whilst at home it works well, in urban environment, in department stores, in hotels often it gets sluggish. Not enough bandwidth. In general it is not because there is too much demand in terms of absolute bandwidth but because there are too many devices accessing the local network, interfering with one another and leading to a decrease in the network throughput.

In the XIX century Maxwell worked out his field equations that basically tied together the magnetic and electric fields. Along with that it came the realisation that the two are interchangeable (Lorentz reciprocity). An electric field creates a magnetic field and the other way round. The point of conversion between the two is the antenna (a wire is an antenna too... but an antenna is designed to maximise this conversion capability). Hence you can use the same antenna to create a magnetic field that carries the signal in space (transmission) and to create an electric field by detecting a magnetic field in the surrounding air (reception).

The antenna is connected to an electronic circuit that either creates an electric field that the antenna will broadcast in terms of magnetic field or analyses an electric current created by the antenna detecting a magnetic field.  This is normally called half duplex. At any single instant the antenna is used as a receiver or as a transmitter. The use of the antenna as a transmitting element or as a receiving element is done through a device called a "circulator" (the ferrite bar in old radios).

At Columbia University researchers have found a way to put all of this into a single chip and to use the antenna to transmit and receive at the same time (full duplex). This makes the WiFi router much smaller since everything is now embedded into a single chip, less expensive (again because one chip does it all) and it doubles the capacity since now the antenna receives and transmits at the same time.

A big boost to WiFi, both in terms of performance and in terms of economics!

Author - Roberto Saracco

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