Scientists at the Tokyo Institute of Technology (Tokyo Tech) have developed a wireless powered relay network for 5G systems. The proposed battery-free communication addresses the challenges of flexible deployment of relay networks.
The researchers say the design is both economical and energy efficient, and such advancements in 5G communications could create huge opportunities for a wide variety of industries.
The ever-increasing demand for wireless data bandwidth does not appear to be slowing down for the foreseeable future.
Millimeter wave, a short wavelength spectrum, has shown great potential in 5G communications and beyond.
To take advantage of high-capacity millimeter wave frequencies, phased array antennas (antenna elements that work together to amplify signal strength in a specific direction) are modified.
However, the current use case is limited to line-of-sight propagation. As a result, relay nodes are being considered for non-line-of-sight communication (see figure below).
While relaying can provide improved bandwidth, coverage and reliability, the flexible deployment of a relay network poses some challenges.
The main challenge in relay networks is the power supply. A typical relay node has its own power supply or is connected to an external power source.
The team of scientists at Tokyo Tech, led by Professor Kenichi Okada, has proposed a wirelessly powered 28GHz phased-array relay transceiver for the 5G network.
Their work is scheduled for presentation at the 2021 Symposia on VLSI Technology and Circuits, an international conference exploring emerging trends and new concepts in semiconductor technology and circuits.
To realize the proposed design, a vector summing backscattering technique is used. The transmitter works as a backscatter with 24GHz local oscillator (LO) and 4GHz intermediate frequency (IF) signals.
“Backscatter communication makes it possible to harvest energy from incident signals and reflect back parts of the same signals as the data is modulated.
In this design, backscatter converts the 5G New Radio (5G NR) spectrum at 4GHz and broadcasts it at 28GHz,” Okada said. The transmitter also acts as a phase shifter, allowing it to change the phase of an incoming signal.
and phase shift capabilities of the transmitter facilitate the formation of a beam, whereby an array of antennas can be controlled to transmit signals in a specific direction.
The result is that information is transmitted more efficiently with less interference. The operation of the receiver and rectifier is a Another critical feature of the transceiver.
Passive phase shifters and power combiners (which combine power with multiple ports) are used to amplify the received signal power for wireless power transmission (WPT).
The proposed rectifier works like a self-heterodyne mixer. In other words, the rectifier splits and recombines an incoming beam with a modulated far sie of itself.
It also works as a full-wave rectifier with the 24GHz WPT signal. The full phased array relay transceiver is configured in an area of only 1.8 mm2. In receive mode, the wirelessly powered 4×8 array module produces 3.1 mW of power.
In transmit mode, it produces -2.2 dBm saturated equivalent isotropic radiated power (EIRP), which is the output power radiated from an antenna in one direction.
The vector-summing backscatter covers a 360 ° phase range with 7-bit phase resolution and consumes only 0.03 mW in both transmit and receive mode.
Okada added, “The proposed battery-free transceiver improves 5G connectivity by serving as a repeater between indoor and outdoor environments.
This, in turn, will improve user experiences and create new opportunities for operational efficiency in the Internet of Things, industrial automation and new communication services. ”