Analysis and Optimization of an Intelligent Reflecting Surface-Assisted System With Interference

Statistical CSI-Based Design for Reconfigurable Intelligent Surface-Aided Massive MIMO Systems With Direct Links

“…However, this feature no longer holds for RIS-aided mMIMO systems. We can find that both the signal term in (8) and interference term in (9) are on the order of O(M 2 ), which means that a large M will make the signal-interference-ratio converge to a constant. Thus, a basic question is that whether this additional interference will limit the gain of RIS.…”

“…Since rich scatters often exist near the ground, we use Rayleigh fading model to express the direct links between the BS and users as [4], [8], [9]. The channel of direct links D ∈ C M ×K can be written as…”

“…The BS decides the MRC matrix by estimating the overall instantaneous channel matrix G + D. At the beginning of each coherence interval, users will transmit the orthogonal pilot sequences to the BS, and then the BS uses the received pilot signals to estimate the overall M × K channel G + D by using the same method in traditional mMIMO systems [15]. We assume this channel is perfectly estimated as in [8], [9] which serves as an upper bound for practical systems, and the extension to imperfect CSI scenario is left for our further work. Thus, using its perfect estimates, the BS can configure the MRC matrix as (G+D) H , and process the received signal as…”

“…Different from the above instantaneous channel state information (CSI)-based contributions, extensive research attention has been shifted to exploit statistical CSI to design the phase shifts of RIS [8]- [14], since it can greatly reduce the channel estimation overhead and computational complexity. Specifically, RIS-aided single-user systems with and without interference were studied in work [8] and [9], respectively.…”

“…Different from the above instantaneous channel state information (CSI)-based contributions, extensive research attention has been shifted to exploit statistical CSI to design the phase shifts of RIS [8]- [14], since it can greatly reduce the channel estimation overhead and computational complexity. Specifically, RIS-aided single-user systems with and without interference were studied in work [8] and [9], respectively. The authors in [10] correlated Rayleigh model, the asymptotic minimum signalto-interference-plus-noise ratio (SINR) and energy efficiency optimization were investigated in work [11] and [12], respectively.…”