Full and Half Duplex for Future Cell Phone Networks

I wrote in earlier in New Full Duplex Radio Chip Transmits and Receives Wireless Signals at Once posting about article New Full Duplex Radio Chip Transmits and Receives Wireless Signals at Once – IEEE Spectrum that told about a new chip that makes full dupled radio communications (tranmitting and receiving at the same frequency time at the same time).A new chip by Columbia University researchers uses a circulator made of silicon transistors to reroute signals and avoid interference from a transmitter and receiver that share the same antenna. The chip enables them to work around the principle of Lorentz Reciprocity, in which electromagnetic waves are thought to always travel along the same path both forward and backward. If this technology work well, the promise is that this technology instantly doubles data capacity on wireless links. for example the CoSMIC (Columbia high-Speed and Mm-wave IC) Lab full-duplex transceiver IC can enable simultaneous transmit and receive at the same frequency and researchers are now working on testing their system with a Wi-Fi network.

Looks interesting. I expect to see how well this works in real life – is it practical?

A new article Finding the Perfect Blend of Full and Half Duplex for Future Cell Phone Networks tells that the idea for practical full duplex radio started in 2007.  The sales pitch for full duplex is a powerful one: these new radios could instantly double the capacity of today’s wireless networks by transmitting and receiving signals on the same frequency, at the same time. But in reality, transmitting and receiving messages at the same time on the same frequency has an unfortunate side effect. It causes twice as much interference as performing each function in turn or on separate bands. So while full duplex radios can dramatically improve spectrum efficiency, the resulting interference means more connections would be lost if a network were constructed wholly of them. Now researchers are studying how wireless engineers can get the best of both worlds by blending full and half duplex radios into the same network. The result is that wireless engineers could tweak the mix of full and half duplex cells in a network: more full duplex cells delivered higher spectrum efficiency at the cost of a few more dropped calls and featuring more half duplex units improved coverage at the expense of overall efficiency. Controlling the transmission power becomes more important in full duplex network than what it has been eariler.