This paper explores the combination of transmit side Space Shift Keying (SSK) and Reflecting Metasurfaces (MTS) in a Multiple-Input Multiple-Output (MIMO) downlink transmitter aimed at advancing the next-generation communication systems. We perform a Pairwise Squared Euclidean Distance (PSED) analysis, which reveals that a simple transmit MTS-SSK scheme – where MTS elements either apply no phase offset or introduce random phase offsets – unexpectedly outperforms a more complex Reconfigurable Intelligent Surface SSK (RIS-SSK) scheme from existing literature, where MTS phases are optimized through feedback of the estimated channel from the receiver to the MTS. This surprising result underscores the potential of an unoptimized MTS as a simpler and more effective alternative to RIS for downlink MIMO-SSK systems. Additionally, we propose a novel approach called RIS-aided Spatial Amplitude Phase Modulation (RIS-SAPM), which overcomes the performance limitation of the MTS-SSK at low values of spectral efficiency. We substantiate these findings by extensive theoretical and simulation-based analysis presented in this paper.

A conventional Direction of Arrival (DoA) estimation algorithm at a GNSS (Global Navigational Satellite System) receiver equipped with a phased array of antennas cannot classify whether the estimated DoA corresponds to the desired GNSS satellite or an interfering source. Furthermore, the GNSS signal is often a low-power spread-spectrum signal that lies below the receiver noise floor. These limitations hinder the application of beamforming in the direction of the GNSS satellite while suppressing the interfering sources. To address this challenge, we introduce a novel two-dimensional (2D) space-frequency DoA estimator and beamformer. Our proposed approach (i) elevates the low-SNR (signal-to-noise ratio) GNSS signals above the noise floor, (ii) leverages the known spectral density of GNSS signals for DoA and FoA (frequency of arrival) estimation, and (iii) performs computationally-efficient spectral domain beamforming and interference nulling. We provide analysis and simulation results to validate the proposed concept.

This paper introduces a novel blind iterative projections algorithm to address challenges associated with codebook-based beamforming in 5G and beyond systems. In contrast to existing methodologies, our proposed algorithm eliminates quantization noise and search space scanning latency. The blind nature of our approach capitalizes on information-bearing symbols, yielding performance close to theoretical expectations. In contrast to the prevalent iterative least squares (LS) algorithms in the literature, our proposal does not necessitate the constant modulus or finite alphabet constraints on the desired signal. This makes our algorithm more general and allows us to demonstrate its stability analytically and capability to perform singular value decomposition (SVD) of the received signal matrix. Our algorithm achieves SVD optimality with lower computational costs than conventional SVD methods. We present an analysis of the Signal to Noise Ratio (SNR) at each iteration, elucidating the impact of batch size and noise variance on the SNR gain at convergence. We apply our proposed algorithm to receive-side hybrid beamforming and show that it offers superior performance compared to various existing approaches documented in the literature.

Smart antenna systems have been considered for base station (BS) and mobile station (MS) to improve spectral efficiency and link quality. The newly emerging 3rd generation mobile (W-CDMA and cdma2000) systems are required to support high bit rate services. This type of high bit rate traffic inevitably consumes a significant amount of capacity and causes considerable interference to low data rate users. Under these circumstances, the smart antenna system is a good candidate to mitigate this interference and keep link quality at adequate levels. One of the crucial components, which can be very complex, is the searcher whose functionality is to continuously search for new multipath signals for combining. A spatio-temporal searcher structure is proposed to enhance the detection capability of the multipath traffic channel searcher. This structure basically employs a spatio-temporal signal structure to search for a new signal. The detection and false alarm probabilities of the new and conventional schemes are calculated and numerical examples of mean acquisition time are given.

We reformulate several different models of antenna array enabled W-CDMA receivers operating in a frequency selective multipath fading channel. We study the problem of full exploitation of both spatial diversity offered by the antenna array and temporal diversity offered by the RAKE while suppressing the interference.