Full-Duplex Radio Integrated Circuit Could Double Radio Frequency Data Capacity

Zothecula writes Full-duplex radio communication usually involves transmitters and receivers operating at different frequencies. Simultaneous transmission and reception on the same frequency is the Holy Grail for researchers, but has proved difficult to achieve. Those that have been built have proven complex and bulky, but to be commercially useful in the ever-shrinking world of communications technology, miniaturization is key. To this end, engineers at Columbia University (CU) claim to have created a world-first, full-duplex radio transceiver, all on one miniature integrated circuit.

Comments

Re:One question:

[DarkOx]

Is the spectrum that crowded that we need this?

The parts of the spectrum that have bandwidth enough for most of today's applications AND good signal propagation characteristics certainly are.

Re:Hmm

[cripkd]

Have you seen the CPU simulations in Minecraft?

Article is wrong. Transceivers do this already.

[gavron]

The article is misleading. Transmission and reception on the same "frequency" is done today. However, there's some other "discriminator" in the signal. Either modulation method, phase, shift, orientation, or "something" is different so that the receive and transmit don't collide.

This article -- despite its misleading introduction -- talks about a limited application whereby RX and TX can occur using the same frequency *BAND* (they say "spread spectrum") and allow full-duplex communication. The advance is that this is all on one chip.

What would be truly revolutionary, like the example of two people talking to each other at the same time, is the ability to transmit and receive using the *same* exact method by both transceivers. THAT would be the holy grail.

Not there yet.

E

Already in use elsewhere (such as Gig Ethernet)

[laing]

The (copper) Gigabit Ethernet PHY transmits and receives simultaneously on four wire pairs. It accomplishes this with a hybrid that subtracts the transmitted signal from the one being received. Last year some newer WiFi access points debuted that could do the same thing with RF. (Gigabit Ethernet is technically RF too because each of the four wire pairs operate at around 125MHz. WiFi access points operate in the 2.4GHz and 5.4GHz bands.)

Clarifications

[Anonymous Coward]

Hi all, I was perusing through all the comments, and as one of the authors of the work, I thought I would clarify some of the points that were raised to aid the discussion: 1. The chip targets same-channel full duplex, meaning the transmitter and the receiver work in the same frequency channel at the same time, and are not separated by polarization, modulation format etc. Therefore, since transmitted signals are around +20dBm and receiver sensitivity levels are around -90dBm, nearly 110dB of suppression through isolation (across a pair of antennas or a circulator) and echo (aka self-interference or SI) cancellation must be achieved (as one of the people above has correctly pointed out). Such a high degree of SI cancellation requires that SI cancellers be implemented in all domains (RF, analog and digital, each yielding a part of the total SI suppression). 2. As one of the people above has pointed out, even if the signals were separated in modulation format for instance, the transmitter SI would be so powerful that it would saturate the receiver front end before modulation-format-based separation can be achieved in the digital domain. So echo cancellation at the receiver front end is required. 3. As someone points out, circulators and echo cancellers have existed for quite a while and have been implemented in many ways. The innovation here is that we perform echo or SI cancellation at RF in a single chip, which has not been done before. 4. Moreover, the SI cancellation approach can tackle echos that experience significant delay (as high as 20ns) while still fitting with an IC form factor through the use of on-chip reconfigurable high-Q filters, enabling cancellation of wideband signals (>20MHz enabling use for WiFi). 5. Finally, indeed the varying environment is a challenge and the RF and digital SI cancellers need to be reconfigured periodically (milli-seconds). Hope this helps.

Re:Clarifications

[CoSMIClab]

Some more clarifications: 6. The chip has been fully tested, and is able to provide the required SI cancellation so that the desired signal can be received without distortion in the presence of the powerful transmitter echo. What remains to be tested are rate gains when several of these chips are networked. This is not that straightforward because today's networks are designed for half-duplex nodes, not full-duplex. So new scheduling concepts etc. need to be developed, which is a topic of research. 7. Echo cancellation is certainly not old technology. While echo cancellation techniques exist, they use techniques that cannot be integrated into an IC (e.g. cm-long transmission lines to replicate 10s of nanoseconds of delay spread, photonic techniques etc.). The innovation here is a technique that can replicate the delay spreads of the echo at RF frequencies on an IC.