Full Duplex Technology Would Double Cellular Capacity

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By Michelle Choi, an insider at Lease Advisors

Have you ever wondered why police dispatchers hold a button on their radios to speak, and wait for a response to come through? The reason they cannot talk at the same time as the person on the other end is radio self-interference—the inability for transmission and reception to occur simultaneously on the same frequency. Also called half duplex, current 3G and 4G networks have been unable to overcome this shortcoming in network efficiency until now. Multiple efforts to develop full duplex radio are in the works in the hope that someday cellular capacity will double and radio signals will be able to coexist on the same frequency. This accomplishment would facilitate heavy data traffic, save carriers billions of dollars on spectrum licensing auctions, and potentially allow carriers and government to share spectrum without issue.

Today’s networks transmit, and then receive, in turn and on separate frequencies. Most mobile networks are built around two blocks of spectrum: one for upstream signals received from mobile devices and another for downstream or outgoing signals. Outgoing signals are 10 billion times stronger than incoming signals that could be drowned out at cell tower base stations. To understand the difference between the two, imagine trying to listen to someone whisper from far away while someone is yelling right next to you. Still, full duplex could be achieved via strategically placed transmitters and receivers, allocating transmission to large base stations and reception to small base stations, and developing a scheduling algorithm by identifying transmission power. The new technology would streamline current networks of infrastructure and spectrum.

There are numerous efforts to pursue full duplex including those by Fujitsu, a team at Columbia University, startup Kumu Networks, and University of California Riverside researchers, each with different approaches. These groups have developed full duplex radio integrated circuitry, self-interference canceling algorithms, and in-radio signal-cancelling circuitry so far. Integration into the coming 5G network remains a challenge as does reduced battery life and the task of navigating tedious regulation. Once achieved, however, full duplex could greatly improve current standards in network speeds using half the amount of spectrum, maximize spectrum and alleviate auction pressures, and more. This is definitely a game changer.

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