Operator coexistence in IRS-assisted mmWave networks: A wideband approach

Abstract

In sixth generation (6G) mobile networks, the push towards high-frequency bands for ultra-fast data rates intensifies the challenges of signal attenuation and reduced coverage range. Intelligent reconfigurable surfaces (IRSs) present a promising solution to these challenges by enhancing signal coverage and directing reflections, which also contribute to minimize loss. However, there are multiple challenges associated with IRS, which have to be addressed before full incorporation of this technology into existing networks. A key issue arises from the inability of IRS to filter out non-target signals from other frequency bands due to lack of bandpass filtering. In areas where multiple wireless operators are spatially nearby, even if they use different frequency bands, this may cause unwanted reflections that may degrade their communication performances. To address this challenge, we previously proposed a solution, which relied on partitioning an IRS into sub-surfaces (sub_IRS) and dynamically assigning operators to these sub_IRS. Results have shown that a proper assignment of wireless operators to sub_IRS can improve the overall performance compared to a random assignment. In this paper, we introduce a wideband approach, demonstrating that the impact from unwanted reflections can be mitigated by using wideband channels, as the average signal to noise ratio (SNR) across subcarriers is less adversely affected. This approach leverages frequency diversity to reduce SNR variance, as some of the subcarriers may be negatively affected while others benefit, resulting in maintaining a more consistent and robust system performance in the presence of IRS-induced unwanted reflections. Simulations and real-world measurements confirm that the deployment of wideband IRS provides a robust strategy for combating inter-operator reflections in next generation IRS-assisted networks. Additionally, the wideband approach comes at no additional necessity for centralized resource control in future multi-operator networks. According to simulations, the SNR variance for a 1.28 GHz channel is approximately 20 dB lower than that of a 10 MHz channel when coexistence is considered. Similarly, measurements confirm a threefold reduction in SNR variation when transitioning from narrowband (10 MHz) to wideband (320 MHz) transmission. In overall, the usage of wideband channels in this context allows the system to be more stable and predictable.