Maximizing the IRS’s Gains in NLOS Communication through Optimal Positioning

Abstract

Background: Recently, an IRS has been proposed as a low-cost and effective solution for performance improvement in wireless communication. However, the configuration and setup necessary to derive optimal results have not been identified yet. Objective: The paper seeks to build the knowledge by investigating the effects of IRS in the LOS and NLOS environment to verify the achievable gains from each and examine how different IRS positions impact the BER. Methods: An IRS model was simulated in MATLAB to investigate the channel capacity gain of an IRS in LOS and NLOS scenarios for the verification of performance gains. Further, the effects of the IRS positioning (with respect to transmitter and end-user) on the BER were investigated. Results: The channel capacity of an IRS system was found to be lower by 12Mbps compared to that of a direct link in a LOS scenario. This demonstrates that a passive IRS is only beneficial in the absence of a line of sight. In the case of a NLOS, for an SNR of 50, MIMO transmitter diversity and receiver diversity had channel capacities of 1.0 Mbps and 4.5 Mbps, respectively while the IRS system achieved 22 Mbps. As such, it is more beneficial to create an alternative path via the IRS than to increase the number of transmit or receive antennas. The positioning of the IRS had a significant impact on the BER. From the results, positioning the IRS mid-way between the AP and STA led to up to 57.69% improvements in BER compared to close to STA or close to AP arrangements. Conclusion: The results prove that an IRS is a cost-effective, low-power consumption solution for overcoming challenges associated with NLOS communication. The work also identified the ideal positioning of the IRS to be the midpoint between AP and STA, for the WLAN system. Further research will be needed to verify performance in other systems.