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.

In this paper, we investigate the secrecy performance of a full-duplex (FD) non-orthogonal multiple access (NOMA) relay system under the presence of multiple non-colluding eavesdroppers over Rayleigh fading channels. Furthermore, to improve legitimate link's capacity, the partial relay selection (PRS) scheme is applied to choose the best relay. To evaluate the secrecy performance, we derive the closed-form expressions of the secure outage probability (SOP) of each user, the overall SOP and the sum effective secrecy throughput (EST) of the considered FD-NOMA relay system. We compare the SOP of the FD-NOMA relay system with that of the half-duplex (HD)-NOMA system and the SOPs of FD-NOMA relay system in the cases that PRS and multiple-relay (MR) schemes are employed at multiple relays. Monte-Carlo simulations verify the correctness of all derived mathematical expressions. Numerical results show that thanks to utilizing FD relays and PRS scheme, the considered FD-NOMA relay system has superior secrecy performance than other systems. Furthermore, increasing the number of FD relays, enhancing their self-interference cancellation capability, and selecting a suitable transmission power help to reduce the SOP of the considered FD-NOMA relay system. Meanwhile, the EST rapidly increases with the equivocation rate of the eavesdropping channel then gradually reaches the saturated maximum value.

In this paper, we analyze the performance of cooperative spectrum sharing single-carrier (SC) relay systems. Taking into account the peak interference power at the primary user (PU) and the maximum transmit power at the secondary user (SU) network, two separate power allocation constraints are formed. For a two-hop decode-and-forward (DF) relaying protocol and two power allocation constraints, two relay selection schemes, namely, a full-channel state information (CSI)-based best relay selection (BRS) and a partial CSI-based best relay selection (PBRS), are proposed. The distributions of the end-to-end signal-to-noise ratios (e2e-SNRs) for the four cases are derived first, and then their outage probabilities and asymptotic outage probabilities are derived in closed-form. The derived asymptotic outage probabilities are utilized to see different diversity gains. Monte Carlo simulations have verified the derived diversity gains for the four different cases. We also present upper bounds on the ergodic capacities for two particular cases.

Hardware impairments (HI) always exist in wireless devices, especially in low-cost devices. However, due to the complexity in mathematical derivation, the studies about wireless networks usually neglect the HI, particularly for full-duplex relaying (FDR) systems. In this paper, we consider the impact of the HI on the outage probabilities (OPs) and ergodic capacities (ECs) of one-way (OW) and two-way (TW) amplify-and-forward (AF) FDR system. We also take into account the residual self-interference (RSI) due to the imperfect self-interference cancellation (SIC). This RSI appears at the FDR node of the considered HI-OW-AF-FDR system and all nodes of the considered HI-TW-AF-FDR system. Through mathematical analysis, we successfully derive the exact expressions of the outage probabilities and ergodic capacities of HI-OW-AF-FDR and HI-TW-AF-FDR systems. Monte-Carlo simulations are used to validate all analysis results. Numerical results show the strong impact of the HI on the OPs and ECs of these systems. On the other hand, the impact of the HI is stronger than that of the RSI. Therefore, besides SIC techniques, all methods that can reduce the HI need to be applied to improve the system performance.

Although the theory of nonorthogonal multiple access (NOMA) has been widely investigated, so far, there is a lack of applying beamforming into NOMA systems. In this article, we propose a multiple-input and multiple-output (MIMO)-NOMA system, where all users in the whole system are divided into multiple clusters to reduce the inner interference. Next, the superpositioned signals at base station are beamed to the relays, and then, the relays communicate with the users through superposition coding in the power domain. We derive the exact expressions of the outage probability of each user and the ergodic capacity (EC) of each cluster in both cases, i.e., perfect successive interference cancellation (SIC) and imperfect SIC, taking into account the Nakagami- $m$ fading channels and imperfect channel state information (CSI). We also compare the outage performance and the EC of our proposed MIMO-NOMA relay system with an orthogonal multiple access (OMA) relay system. Monte Carlo simulations are used validate the derived mathematical expressions. Numerical results show that the outage performance and the EC of each user and the whole system are reduced remarkably due to the imperfect CSI but get better as the fading severity is less. Moreover, the EC of our proposed MIMO-NOMA relay system is higher than that of the OMA relay system.

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.