This paper proposes and analyzes a downlink multi-antenna multi-user system with rate-splitting multiple access (RSMA) scheme. In this framework, we consider the error probability when the base station (BS) transmits both long and short packet information to multiple cell-edge users. Our approach begins with the beamforming vector analysis, and employs the cumulative distribution functions (CDF) of signal-interference noise ratio (SINR). To map the dependencies of common and private streams of RSMA for the SINR, we adopt a two-dimensional signal constellation, which revealed the relationship between power allocation factors and modulation types. This relationship affects the decision boundaries of the modulation schemes. To evaluate the system performance, exact and asymptotic expressions for the block error rate (BLER) and bit error rate (BER) are derived over Nakagami fading channels. The optimal power allocation coefficient to minimize BLER under varying channel uses is formulated and detected through optimization problem and numerical results. Fairness in BER among all users is considered by accounting for the number of antennas and the adopted power allocation strategy. The advantages of RSMA are further verified through comparisons of BLER/BER with non-orthogonal multiple access (NOMA) systems. These findings underscore the potential of RSMA to significantly enhance reliability. The derived expressions are tractable, validated through comparisons with Monte Carlo simulation results, and offer reduced computational complexity and faster execution compared to the simulation-based outcomes. The results show the closest alignment between simulations and the derived analytical expressions.

This paper considers and analyzes the performance of a non-orthogonal multiple access (NOMA) system using finite-size data packets with the assistance of active reconfigurable intelligent surfaces (ARISs) mounted on an unmanned aerial vehicle (UAV). This work aims to enhance communication efficiency in scenarios that require low latency and high reliability. The exact and asymptotic closed-form expressions for the block error rate (BLER) and average achievable rate (AAR) of the considered UAV-ARIS-NOMA system with short packet communication under imperfect successive interference cancellation (SIC) are derived. The results analysis indicates that the number of reflection elements strongly influences the diversity order. The considered system meets ultra-reliable and low-latency communications (URLLC) demands with 99.999% reliability, and the ARIS model's BLER reduces by 290% compared to the passive RIS (PRIS). Moreover, the gap between the AAR of ARIS and PRIS is up to 40% when configuring eight reflection elements. The system's AAR reaches saturation by adjusting the ARIS amplification factor to three power units. When channel uses exceed 300, the system's transmission rate meets the Shannon rate. Moreover, simulation results are introduced to verify the theoretical analysis and offer insights into optimizing power allocation and UAV altitude to minimize BLER.

This paper analyzes and solves the optimization problem of the performance of a multi-antenna unmanned aerial vehicle (UAV)-aided NOMA multi-user pairing system. Based on the approximation of the Gaussian-Chebyshev quadrature and incomplete Gamma function, we successfully derive the exact and asymptotic closed-form expressions for the block error rate, throughput, and goodput of the system. Moreover, we also provide other metrics such as the latency, reliability, and age of information (AoI). The results indicate that the considered system meets the requirements of ultra-reliable and low-latency communications (URLLC). Particularly, its reliability is higher than 99.99% and latency is less than 1 ms. The optimization of the UAV's altitude, block length, and the number of transmission bits to maximize the throughput and minimize the latency and AoI of the considered system is also studied by using iterative algorithms. Furthermore, we propose an algorithm to optimize the transmission power of UAVs to maximize the system's energy efficiency. The greedy algorithm is used to schedule paired users and achieves better performance compared to the random schedule. Moreover, applying multiple antennas and maximum ratio transmission can significantly improve the latency and AoI performance of the considered system. The accuracy of analytical frameworks is verified by simulation results.

In this work, we consider a base station (BS) mounted on an unmanned aerial vehicle (UAV) called as an aerial BS (ABS). The ABS is equipped with multiple antennas to assist two pairs of users in nonorthogonal multiple access (NOMA) scheme, and it serves as a relay station to forward the data from the uplink to the downlink of ground IoT users in half-duplex mode. Moreover, the communication power of ABS is harvested from ambient radio-frequency (RF) sources, such as television (TV) and radio signals via the time switching mechanism. In order to improve the efficiency of harvested energy, multiple antennas at the TV/radio tower and the maximal-ratio transmission (MRT) scheme are applied. The proposed ABS RF energy harvesting system overcomes the problem of connectivity of ground IoT users and the energy limitation of devices. The system performance is evaluated in terms of the outage probability of each pair of IoT users in various urban communication environments. Monte Carlo simulation results are provided to validate the accuracy of the developed analytical results and also demonstrate the performance of the proposed system. The results show that the proposed system achieves better performance than that of benchmark systems and the performance can be improved significantly by adjusting the UAV’s altitude.

In this paper, we investigate the performance of a full-duplex (FD) relay system where multi-antennas are exploited at source and destination. Unlike previous works, the impacts of imperfect channel state information (I-CSI), transceiver hardware noise (THN), and residual self-interference (RSI) are taken into account. We mathematically derive the exact closed-form expressions of the outage probability (OP), symbol error rate (SER), and ergodic capacity (EC) of the FD relay system with I-CSI, THN, and RSI over Nakagami-$m$fading channels. From the derived expressions, the performance of the considered system under the effects of three negative factors (I-CSI, THN, and RSI) is compared with that system in the case of all ideal factors (perfect channel state information (P-CSI), perfect transceiver hardware (P-TH) and perfect self-interference cancellation (P-SIC)), two ideal factors (P-CSI and P-TH, P-CSI and P-SIC, P-TH and P-SIC), or one ideal factor (P-CSI or P-TH or P-SIC). Numerical results show a strong impact of three negative factors on the OP, SER, and EC of the considered FD relay system, especially when the data transmission rate of the system and signal-to-noise ratio (SNR) are high. In particular, OP, SER, and EC go to the floors in the high SNR regime due to the three negative factors. Therefore, when I-CSI, THNs, and RSI exist in the FD relay system, we should use suitable source and relay transmission power to obtain excellent performance while saving energy consumption. Moreover, when two of the three negative factors are large enough, the remaining factor’s impact becomes weaker and may be neglected in certain circumstances.

In this paper, we analyze the performance of in-band full-duplex (IBFD) relay systems that use the decode-and-forward (DF) protocol at the relay under the impact of imperfect self-interference cancellation and hardware impairments. Three practical relay scenarios are considered in our analysis: (i) there is no direct link from the source to the destination; (ii) there is a direct link, but the signal from the source is considered interference; and (iii) there is a direct link, and the signal from the source is cooperatively combined with that from the relaying path. Specifically, we derive exact and asymptotic expressions for the outage probability (OP) of the IBFD system. Based on the OP, the exact expression for symbol error probability (SEP) is also derived. Moreover, in order to cope with the effect of imperfect self-interference cancellation (SIC) due to the full-duplex mode, we propose optimal and suboptimal power calculation methods for the relay to minimize the OP and SEP. A performance evaluation shows that the IBFD relay system is significantly affected by both imperfect SIC and hardware impairments. However, the optimal power values can help to improve the system performance, significantly.

In this paper, we analyze the performance of a full-duplex (FD) amplify-and-forward (AF) relay system with imperfect hardware. Besides the aggregate hardware impairments of the imperfect transceiver, we also consider the impact of residual self-interference (RSI) due to imperfect cancellation at the FD relay node. An analytical framework for analyzing the system performance including exact outage probability (OP), asymptotic OP, and approximate symbol error probability (SEP) is developed. In order to tackle these impacts, we propose an optimal power allocation scheme which can improve the outage performance of the FD relay node, especially at the high signal-to-noise ratio (SNR) regime. Numerical results are presented for various evaluation scenarios and verified using the Monte Carlo simulations.

In this paper, we propose a spatially modulated space-time block coding scheme, called DT-SM, by combining the conventional double space time transmit diversity (DSTTD) with spatial modulation. First, we design a set of four basic spatial constellation (SC) codewords and an extended set of 16 SC codewords for four transmit antennas by using computer search based on the rank and determinant criterion. We then present a generalized algorithm to design SC codewords for an arbitrary number of transmit antennas greater than four. Compared with DSTTD, the proposed scheme attains the same transmit diversity order, while offering higher spectral efficiency. Besides, we derive a union bound for the bit error rate (BER) of the proposed DT-SM scheme in a quasi-static Rayleigh fading channel with spatial correlation. In order to achieve the performance of maximum-likelihood (ML) estimation at reduced detection complexity, we develop a sphere decoder based on the conventional Schnorr-Euchner sphere decoder. BER performance and detection complexity of the DT-SM scheme are evaluated by computer simulations. It is shown that the proposed DT-SM outperforms many existing MIMO and SM-based MIMO schemes at reasonable detection complexity, even in correlated MIMO channels.

This paper proposes a low‐complexity signal estimator at the relay node for a spatially modulated physical‐layer network coding system. In the considered system, the two terminal nodes use spatial modulation to transmit their signals to the relay node during the multiple access phase. Based on the channel quantization method, we propose a low‐complexity estimator which can detect both antenna indices and M‐QAM symbols using successive interference cancellation (SIC). Moreover, we design signal constellations for a combined signal component at the relay for arbitrary M‐QAM modulation. The obtained constellations allow further reduction of the computational complexity of the estimator. Performance evaluations show that the proposed estimator can achieve near‐optimal error performance while requiring significantly less computational complexity compared with the maximum‐likelihood detector, particularly with high‐order modulation.

This paper proposes an enhanced sub-optimal detector for the High Rate-Spatial Modulation (HR- SM) systems presented in [1] by incorporating the ISQRD detector previously proposed in [2] with a new search space. The proposed decoder, called Enhanced ISQRD, achieves not only significant improvement in the bit error rate (BER) performance but also complexity reduction as compared to the ISQRD detector. In addition, we propose a new bit mapping approach that allows the HR-SM system to improve its BER performance. Simulation results and complexity analysis are presented to verify the effectiveness of the proposed approaches in terms of performance improvement and detection complexity reduction when they are applied to the HR-SM systems.

In this paper, we present a new upper bound for the bit error probability (BEP) of the so-called Space Time Block Coded Spatial Modulation (STBC-SM) system introduced by E. Basar et al. in [1] over a quasi-static Rayleigh fading channel. Based on the Verdu's theorem [2], the concept of the spatial constellation (SC) codewords and maximum likelihood (ML) decoder in [3], the upper bound is obtained by eliminating a number of redundant pairwise error probabilities (PEPs). Our approach leads to a new upper bound, which is tighter than the union bound. Consequently, it allows us to evaluate the bit-error performance of STBC-SM systems more exactly, particularly when the signal-to-noise power ratio (SNR) is sufficiently high.

This paper proposes a high rate spatial modulation transmission scheme based on the concept of Spatial Constellation (SC) and SC codewords introduced in [1]. In the proposed scheme, transmitted signal vectors are generated by multiplying spatial SC codewords with constellation symbols drawn from a conventional QAM or PSK constellation. The entries of SC codewords will determine how the constellation symbols are weighted and which transmit antennas among a total of nT transmit antennas are activated to transmit the signals. Different SC codewords allow us to have different ways to transmit the constellation symbols. Thus, information bits are born not only by constellation symbols but also by SC codewords. The additional spectral efficiency offered by SC codewords is proportional to the number of SC codewords which can be designed for each antenna configuration. A new low-complexity maximum-likelihood (ML) decoder is also devised for signal recovery. In addition, a theoretical union bound on the bit error probability is derived. Simulation results, supported by the theoretical upper bound, are given to compare bit error rate (BER) performance of the proposed scheme with those of existing MIMO transmission counterparts in the literature for various antenna configurations.

This paper presents a design of two-way two-hop relay network using physical layer network coding (PNC) in which multiple antennas are used at all nodes. For transmission over the multiple-input multiple-output channels, the Alamouti's space-time block code (STBC) is used for transmission while linear detection is used for signal estimation at all nodes. In order to facilitate linear detection, we develop an equivalent multiuser STBC model for the proposed network and design the sum-and-difference matrix which is suitable for signal estimation. Simulation results show that the proposed network achieves diversity order 2 with polynomial complexity.

This paper proposes a multiple-input multiple-output (MIMO) transmission scheme for M-ary modulations, called Spatially Modulated Orthogonal Space-Time Block Coding (SM—OSTBC), based on the concept of Spatial Constellation (SC) codewords introduced by Le at el. . In the proposed scheme, transmit codeword matrices are generated by multiplying SC matrices with codewords constructed from Orthogonal Space-time Block Codes (O—STBC). The maximum spectral efficiency of the proposed scheme is equal to (n_T-2+ log_2 M) bpcu, where n_T is the number of transmit antennas and M is the modulation order. The SC matrices provide a means of carrying information bits together with the O—STBC codewords and allow the SM—OSTBC scheme to achieve second-order transmit diversity by satisfying the non-vanishing determinant property. A systematic method to design the SC codewords for an even number of transmit antennas greater than 3 is presented. A single-stream maximum-likelihood (ML) decoder, which requires a low computational complexity thanks to the structure of the SM—OSTBC codewords and to the orthogonality of the O—STBCs, and a sphere decoder with further reduced signal processing complexity are developed. The bit error rate (BER) performance of the proposed scheme is studied by using both theoretical union bound analysis and computer simulations. Finally, simulation results are presented in order to compare BER performance, energy efficiency and decoding complexity of the proposed scheme with those of several existing MIMO transmission schemes.

Recently, lattice reduction aided (ERA) detectors have been introduced into Vertical Bell-Labs Layered Space-Time (V-BEAST) systems to obtain nearly optimal bit error rate (BER) performance for only small additional complexity. In this paper, the layer error characteristics of LRA-V-BLAST detectors are analyzed and compared with those of conventional V-BLAST ones. Two important conclusions are drawn for the LRA-V-BLAST detectors. First, the variation of their mean square error (MSE) within each detection iteration is not as large as in conventional V-BLAST detectors. Second, thanks to lattice reduction there exists an inherent sub-optimal detection order from the last to the first layer. These conclusions allow LRA-V-BLAST detectors to avoid optimal ordering to further reduce the complexity. LRA-V-BLAST detectors without optimal ordering are shown to obtain almost the same BER performance of LRA-V-BLAST detector with optimal ordering

In this paper, we propose two minimum mean square error (MMSE)-based multiuser detectors, called the combined MMSE and maximum likelihood (MMSE-ML) multiuser detector and the combined MMSE and successive interference cancellation (MMSE-SIC) multiuser detector, for an uplink space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) system. Both detectors provide significantly improved bit error rate (BER) over the conventional MMSE multiuser detector while requiring the same complexity order. Moreover, the combined MMSE-ML detector exhibits better BER than the combined MMSE-SIC, particularly, in a system with a small number of users.

The paper presents a simple method of the maximum SINR (signal to interference plus noise ratio) design of MIMO (multiple input multiple output) communication systems using a TDL (tapped delay line) structure. The transmitter and receiver weights are determined alternately, optimizing one side by fixing the other, and this operation is repeated until the SINR converges. The performance of MIMO systems using the proposed approach is investigated, through computer simulations, and it is demonstrated that, though it requires high computational cost, the TDL structure brings high ability to mitigate the influence of frequency selective fading, particularly when the duration of the delay profile is long. Moreover, experimental results show that the equable distribution of the resources (weights and delay units) to both arrays is a better choice than the concentration of them to one side of the transmitter or receiver.

The subband adaptive array (SBAA) is a method for the parallel implementation of the tapped delay line adaptive array (TDLAA) which possesses high ability to mitigate the degradation of the quality of wireless communications under the environment where plural coherent propagation waves are arriving from different directions (multipath fading environment). This paper presents a unified analytical overview and an evaluation criterion for SBAA accompanied with sampling rate conversion. Here the signal-to-interference-plus-noise ratio (SINR) is adopted as quality factor and the performance of the SBAA under multipath fading is investigated theoretically based on this criterion. As an improvement for the SBAA, the cyclic prefix (CP) which is used in orthogonal frequency division multiplexing (OFDM) communication systems is introduced and experimentally verified to be effective through computer simulations. This paper demonstrates the advantage of this approach from the analytical viewpoint with respect to the correlation matrix in each band.