High-Resolution Programmable Scattering for Wireless Coverage Enhancement: An Indoor Field Trial Campaign

Abstract

This paper presents a multi-bit reconfigurable intelligent surface (RIS) with a high phase resolution, capable of beam-steering in the azimuthal plane at sub-6 Gigahertz (GHz). Field trials in realistic indoor deployments have been carried out, with coverage enhancement performance ascertained for three common wireless communication scenarios. Namely, serving users in an open lobby with mixed line of sight and nonline of sight conditions, communication via a junction between long corridors, and a multi-floor scenario with propagation via windows. This work explores the potential for reconfigurable intelligent surface (RIS) deployment to mitigate non-line of sight effects in indoor wireless communications. In a single transmitter, single receiver non-line of sight link, received power improvement of as much as 40 dB is shown to be achievable by suitable placement of a RIS, with an instantaneous bandwidth of at least 100 MHz possible over a 3 to 4.5 GHz range. In addition, the effects of phase resolution on the optimal power reception for the multi-bit RIS have been experimentally verified, with a 2.65 dB improvement compared to a 1-bit case.

Review Paper on Hardware of Reconfigurable Intelligent Surfaces

“…37 (a), Fig. A multi-bit PIN diode-based RIS capable of beam steering at the sub-6 GHz was proposed in [141]. An indoor field trial was carried out for different scenarios.…”

A varactor-based 1024-element RIS design for mm-waves

“…Compared to the previous references (Trichopoulos et al, 2022)- (Araghi et al, 2022), the proposed unit cell has a higher loss than the 1-bit unit cell presented from (Trichopoulos et al, 2022) and the 2-bit unit cell from (Dai et al, 2020), although both unit cells operate at lower frequencies. The 1-bit unit cell at 28.5 GHz from (Gros et al, 2021) showed a maximum reflection amplitude of -3 dB using PIN diodes, whereas the one from (Rains et al, 2021) can generate a 3-bit phase response with −4.65 dB maximum reflection amplitude at 3.75 GHz. The unit cells from (Pei et al, 2021) and (Araghi et al, 2022) used varactor diodes as tuning elements at 5.8 and 3.5 GHz, respectively.…”

“…Since then, many works have been published in RIS based on PCB solutions with PIN and varactor diodes as tuning elements and patch reflectors (Trichopoulos et al, 2022)- (Araghi et al, 2022). To generate the unit cell reflection phase tunability, patch elements might be connected to parasitic elements (Trichopoulos et al, 2022), (Gros et al, 2021), grounded elements (Pei et al, 2021), (Rains et al, 2021), or between them (Araghi et al, 2022). Also, a different approach was proposed in (Dai et al, 2020) based on a top patch element interaction with a slotloaded plane between it and the ground plane.…”

“…Aiming to increase the number of phase states using PIN diodes, five devices were arranged into a slot-loaded plane in (Dai et al, 2020), producing four different 90 °apart phase states to compose a 2-bit unit cell at 2.3 GHz and another one at 28.5 GHz. The number of phase states was improved by introducing a unit cell with five patches connected by three PIN diodes and one lumped capacitor (Rains et al, 2021). In this way, a 3-bit unit cell with eight distinct phase states biased in a column-wise fashion was demonstrated.…”

Reconfigurable Intelligent Surface: Power Consumption Modeling and Practical Measurement Validation

“…Since P dynamic ≈ 0, varactor-diode-based RIS has potential of achieving low power consumption compared with PIN-diode-based RIS. However, it should be noted that the control circuit of varactor-diode based RIS is often much more complicated, i.e., a varactor diode interfaced with voltage level shifter circuity or DACs, whereas PIN-diode based RIS only needs shift register and FPGA [12]. In addition, most of RISs working in high frequency (i.e., mmWave band) belong to the…”