Tuesday, March 17, 2015

Techy Tuesday: Full-Duplex Chip is Nothing but Hype from Theoreticians

Ol' Backwoods is a seasoned old fart, and when I read hyped-up stuff like this, I just have to speak up:
New technology may double radio frequency data capacityA team of Columbia Engineering researchers has invented a technology — full-duplex radio integrated circuits (ICs) — that can be implemented in nanoscale CMOS to enable simultaneous transmission and reception at the same frequency in a wireless radio. Up to now, this has been thought to be impossible 
[horse hockey! --BE]: 
transmitters and receivers either work at different times or at the same time but at different frequencies. 
The Columbia team, led by Electrical Engineering Associate Professor Harish Krishnaswamy, is the first to demonstrate an IC that can accomplish this. The researchers presented their work at the International Solid-State Circuits Conference (ISSCC) in San Francisco on February 25. 
“This is a game-changer,” says Krishnaswamy. “By leveraging our new technology, networks can effectively double the frequency spectrum resources available for devices like smartphones and tablets.”
Look, this ain't no "game changer", and if these pointy-headed scientists knew anything about practical radio systems, they'd know it sure ain't "impossible" to transmit and receive at the same time. (I worked on systems designed in the 1960's that did just that.)  It's just there's a more power-efficient way to operate a radio system.
Some of y'all know: I am a practicing radio-frequency (RF) design engineer, with over 25 years of experience, spanning products from gas pipeline telemetry to satellite communications to automatic water meter reading. I’m also a ham radio operator, and have been since I was 14 years old. Radio communications is literally my bread and butter, and my life’s work.
And Ol' Backwoods is telling you: this is hype. This is nothing but hyperbole to pump up the public perception of the work of theoreticians who have never designed a practical radio communications system. This is NOT a world-changing technology.
In fact, it’s more power-efficient NOT to do full-duplex transmission, like the old analog cellular phones used to do. Modern cellular and VOIP networks break digitized voice into “packets”, and the receiving of packets is interleaved with transmission of packets, so that the phone does not have to transmit and receive simultaneously. Yes, this adds a delay to the transmission, but unless the two people talking are in the same room (and why?), they don’t care about a slight delay.
Full-duplex voice belongs to a bygone era. Nowadays, it can be emulated by packetized digital voice techniques far more power-efficiently than real full-duplex.
If these people want to solve REAL problems, why don't they work on devices that would make a real difference to spectral efficiency, such as band-selective analog-to-digital converters (ADC's).

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