The use of wireless devices is exploding. Statista, an international research service, estimated in March 2019 that roughly 13 billion mobile devices (e.g., phones, tablets, laptops) were in use worldwide, and Gartner, a global research and advisory firm, predicts that the internet of things will swell that number to more than 21 billion devices by the end of 2020.
The widespread use of mobile devices already creates significant demand on the cellular system that supports all this wireless connectivity, especially at locations, such as an outdoor concert or a sports arena, where large numbers of users may be simultaneously connecting. The ability of current-era cellular technology, or even the proposed next-generation 5G technology, will be severely strained to provide the high data rates and wide-area communication range needed to support the escalating device usage.
The communications community has been looking at in-band full-duplex (IBFD) technology to increase the capacity and the number of supported devices by allowing the devices to transmit and receive on the same frequency at the same time. This ability not only doubles the devices’ efficiency within the frequency spectrum, but also reduces the time for a message to be processed between send and receive modes.
In the article “In-Band Full-Duplex Technology: Techniques and Systems Survey,” published recently in IEEE Transactions on Microwave Theory and Techniques, MIT Lincoln Laboratory researchers from its RF Technology Group — Kenneth Kolodziej, Bradley Perry, and Jeffrey Herd — assessed the capabilities of more than 50 representative IBFD systems. They concluded that IBFD technology incorporated into wireless systems can enhance the systems’ ability to operate in today’s congested frequency spectrum and increase the efficient use of the spectrum.
However, the authors’ cautioned that the potential of IBFD for wireless communications can only be realized if system designers develop techniques to mitigate the self-interference generated by simultaneously transmitting and receiving on the same frequency.
The IBFD systems developed so far are limited in the range they can achieve and the number of devices they can accommodate because they rely on antennas that radiate omnidirectionally. Recently, Lincoln Laboratory researchers have demonstrated IBFD technology that for the first time can operate on phased-array antennas. “Phased arrays can direct communication traffic to targeted areas, thereby expanding the distances that the RF signals reach and significantly increasing the number of devices that a single node can connect,” Kolodziej said.