Hybrid Active Passive Wireless Network Aided by Intelligent Reflecting Surface System Modeling and Performance Analysis

Abstract : Intelligent reflecting surface (IRS) is a new and promising paradigm to substantially improve the spectral and energy efficiency of wireless networks, by constructing favorable communication channels via tuning massive low-cost passive reflecting elements. Despite recent advances in the link-level performance optimization for various IRS-aided wireless systems, it still remains an open problem whether the large-scale deployment of IRSs in wireless networks can be a cost-effective solution to achieve their sustainable capacity growth in the future. To address this problem, we study in this paper a new hybrid wireless network comprising both active base stations (BSs) and passive IRSs, and characterize its achievable spatial throughput in the downlink as well as other pertinent key performance metrics averaged over both channel fading and random locations of the deployed BSs/IRSs therein based on stochastic geometry. Compared to prior works on characterizing the performance of wireless networks with active BSs only, our analysis needs to derive the power distributions of both the signal and interference reflected by distributed IRSs in the network under spatially correlated channels, which exhibit channel hardening effects when the number of IRS elements becomes large. Extensive numerical results are presented to validate our analysis and demonstrate the effectiveness of deploying distributed IRSs in enhancing the hybrid network throughput against the conventional network without IRS, which significantly boosts the signal power but results in only marginally increased interference in the network. Moreover, it is unveiled that there exists an optimal IRS/BS density ratio that maximizes the hybrid network throughput subject to a total deployment cost given their individual costs, while the conventional network without IRS (i.e., zero IRS/BS density ratio) is generally suboptimal in terms of throughput per unit cost.
 EXISTING SYSTEM :
 ? The work in consider a multi-user scenario and maximizes the energy efficiency by designing the AP’s transmit power allocation and the IRS reflections. ? In, the authors maximize the secrecy rate by jointly taking into account the AP’s active transmit beamforming and the IRS’s passive reflect beamforming. ? Through these reflections, an IRS provides the means to intelligently control the propagation environment and boost the received signal at the designated receivers. ? We provide a complete analytical framework in terms of the outage probability, using tools from stochastic geometry.
 DISADVANTAGE :
 ? In particular, for the case with IRS reflect beamforming, we characterize the impact of d0 on the mean signal power and the d0-dependent channel hardening effect to draw useful insights. ? One critical issue is the modeling, design and performance characterization of the IRS-aided multi-cell hybrid wireless network comprising both distributed active BSs and passive IRSs subjected to the inter-cell interference. ? However, the above works only consider a given number of BSs and IRSs at fixed locations, but do not investigate the impact of their spatial random locations on the performance of large-scale hybrid active/passive wireless networks.
 PROPOSED SYSTEM :
 • In, the authors propose lowcomplexity coding-based and selection-based schemes, which can achieve high energy efficiency as well as full diversity order. • The work in proposes an IRS-aided opportunistic beamforming scheme and derive the achieved sum-rate scaling laws; it is shown that the proposed scheme outperforms the conventional one. • Moreover, unlike the works in, we investigate how the association policy with the employed IRSs affects the performance of the network. • In particular, we study the association with a random IRS, with the closest IRS as well as with all IRSs available in the cell.
 ADVANTAGE :
 ? The proliferation of mobile applications and explosive growth of wireless data have been continually spurring enthusiasm in inventing new and innovative wireless communication technologies that would achieve higher spectral/energy efficiency (SE/EE) yet at an affordable deployment/operational cost. ? These new analytical methods jointly yield accurate and efficient characterization of the network SINR distribution and hence its spatial throughput. ? We derive the BS-IRS-UE cascaded channel power statistics, which is new for the IRS-aided hybrid network and essential to our subsequent performance analysis for it. ? Such correlation introduced by randomly distributed IRSs near UE 0 imposes new difficulty to the system-level performance analysis, which is challenging to deal with.

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