Low-Complexity Random Rotation-based Schemes for Intelligent Reflecting Surfaces
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The employment of intelligent reflecting surfaces (IRSs) is a potential and promising solution to increase the spectral and energy efficiency of wireless communication networks. The passive operation of their elements and the fact that they can be deployed on any flat surface, makes them ideal for both indoor and outdoor applications. On the other hand, the capabilities of IRS-aided communications have limitations as they are subject to high propagation losses. To overcome this, the phase rotation at each element needs to be designed in such a way as to increase the channel gain at the destination. However, this increases the system's complexity as well as its power consumption. In this paper, we present an analytical framework for the performance of random rotation-based IRS-aided communications. Under this framework, we propose four low-complexity and energy efficient techniques based on two approaches: a coding-based and a selection-based approach. Both approaches depend on random phase rotations and require no channel state information. In particular, the coding-based schemes use time-varying random phase rotations to produce a time-varying channel, whereas the selection-based schemes, select a partition of the IRS elements at each time slot based on the received signal power at the destination. Analytical expressions for the achieved outage probability and energy efficiency of each scheme are derived. It is demonstrated that all schemes can provide significant performance gains as well as full diversity order.
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