A Study on Fiber-Optic Relaying Scheme Using Spatial Modulation for MIMO Transmissions

In recent years, several approaches have been proposed aiming the optimal joint design of finite impulse response (FIR) multiple-input multiple-output (MIMO) transmitter and receiver. Assuming that the channel input is power constrained and that the channel model is a known FIR MIMO system, it is possible to design high performance transceivers in the presence of additive noise. Unfortunately, most optimal transceivers available so far, do not have fast implementation and simple design approaches. This work proposes a minimum mean square error (MMSE) design approach where constraints are incorporated into the structure of the FIR MIMO transmitter, in such a way that the resulting optimal MIMO transmitter, in the MMSE sense, has inherent fast algorithm implementation. In comparison with the general jointly optimized transceivers recently proposed, the new approach allows substantial reduction in the computational complexity at expense of mild performance degradation.

A channel state information (CSI) feedback algorithm based on scalar quantization is proposed for a multiple-input multiple-output (MIMO) transmission. The performance of the proposed algorithm is evaluated using the effective transmission rate, which incorporates the effect of the CSI feedback overhead on transmission time. Besides that, the power consumed due to the computational complexity of the CSI feedback algorithm is taken into account together with the transmit power when evaluating the energy efficiency. We compare our proposed algorithm to other typical CSI feedback algorithms under correlated channel conditions. Simulation results show that the proposed algorithm enables practical MIMO transmission to achieve an relative transmission rate at 95% of the ideal rate.

This paper investigates the issue of high complexity of digital predistortion for the nonlinear distortion introduced due to crosstalk in addition to the nonlinear distortion generated by a power amplifier (PA) in 2 × 2 MIMO transmitters. This paper proposes a less complex, novel model for digital predistortion (DPD) for linearizing multiple-input multiple-output (MIMO) transmitters. This model is constructed by taking account of both linear and nonlinear crosstalks, along with the fact that the nonlinearity generated due to crosstalk would be lesser than the nonlinearity already available due to PA. For proof-of-concept, it is shown for two different scenarios that proposed model provides similar linearization performance as compared to 2 × 2 PH model with less number of coefficients.

Orbital Angular Momentum (OAM) has been considered as a new dimension in wireless transmission. In Multiple Input Multiple Output (MIMO) system, OAM can also be utilized as the new Degrees of Freedom (DoF) to manipulate the beamforming instead of the traditional Channel State Information (CSI) feedback, so that the computation complexity of the beamforming dramatically decreases, as well as the capacity of the transmission is maintained approaching the upper bound of the MIMO system. For example, this beamforming manipulation with OAM is extremely efficient in the Line of Sight (LoS) MIMO system. In this paper, the mathematical model of the DoF in beamforming manipulation in MIMO with OAM is established. The computation complexity is evaluated, and compared in LoS environment within MIMO, MIMO-OAM, and OAM. The quantitatively simulation confirms the fact that MIMO-OAM has the best trade-off between the capacity and the computation complexity, which gives a consolidated evidence that the MIMOOAM scheme can be adopted as an efficient beamforming scheme in LoS backhaul links between the base station and the self backhaul small cell station, or Near Field Communications (NFC) directly between mobile terminals. Due to these promising applications, MIMO-OAM may become one of the candidate technologies in Beyond 5G (B5G) mobile communications.

An adaptive digital predistortion (PD) technique is proposed for linearization of power amplifiers (PAs) in multiple-input multiple-output (MIMO) transmitters. Instead of constructing a separate feedback path at each PA, we propose a PD technique based on a combined feedback, which adds all the PAs' outputs to form a single feedback. We develop an algorithm for finding the multiple PA characteristics jointly from the combined feedback. The PD parameters are calculated from the identified PA characteristics. Although the proposed method requires more computations for PA identification than the conventional method, its hardware implementation is much simpler and can overcome the crosstalk problem of a radio frequency (RF) selector, which is necessary for multiple feedback selection. The simulation results show that, despite its simple structure, the linearization performance of the proposed method is almost the same as the separate multiple feedback method.

Video monitoring applications for underground rely on wireless train-to-wayside communication systems which require high data rate as well as high Quality of Service (QoS) level. In order to satisfy both constraints we propose a combined source and channel coding approach in the context of MIMO (Multiple Input Multiple Output) video transmission. In the present case, MIMO transmission is based on the PHY layer of IEEE 802.11n Wi-Fi standard currently deployed in a railway tunnels. Two different strategies are studied: first, the association between Multiple Description Coding (MDC) and a STBC (Space Time Block Code) MIMO scheme is considered when no channel information is available at transmitter side. In the case when perfect channel information is available at transmitter side (CSIT), a Singular Value Decomposition of the MIMO channel is possible. This transmission scheme is then associated with scalable video coding, which consists here in the separation of the scene into different Regions Of Interest (ROI). The creation of the regions of interest is based on the Flexible Macroblock Ordering (FMO) technique introduced in the new H.264/AVC compression standard. The stream associated to the area with the maximal perceptual relevance is transmitted on the eigen-channel with the higher gain. Consequently, this strategy which provides unequal protection against channel errors, allows guaranteeing better robustness and acceptable reconstructed video quality at the control-centre. The two different strategies of transmission have been evaluated thanks to realistic simulations. Two antenna configurations representative of real cases encountered in railway tunnels are considered. The channel model is generated by using the correlation based Kronecker model obtained by computing the channel matrix with a 3D ray tracing tool. Simulation results show that the two proposed solutions allow enhancing the reconstructed video quality compared to conventional transmission schemes with no increase of the transmitted power and of the number of radio access points along the infrastructure, even in tunnels in presence of spatial correlation.Keywordstrain-to-wayside communicationsvideo communicationsMultiple Input Multiple Output (MIMO) systemMultiple Description Coding (MDC)Scalable Video Coding (SVC)Kronecker model

Environmental issues and the need to reduce energy consumption for lowering operating costs have pushed power efficiency to become one of the major issues of current research in the field of wireless networks. This paper addresses a number of multiple input multiple output (MIMO) precoding and scheduling techniques across the PHY and MAC layers that can operate under a reduced link budget and collectively improve the transmit power efficiency of a base station, while maintaining the same levels of service. Different MIMO transmission and precoding schemes proposed for LTE, achieving varying degrees of multiuser diversity in both the time, frequency as well as the space domain, are examined. Several fairness-aware resource allocation algorithms are applied to the considered MIMO schemes and a detailed analysis of the tradeoffs between power efficiency and quality of service is presented. This paper explicitly examines the performance of a system serving real-time, VoIP traffic under different traffic loading conditions and transmit power levels. It is demonstrated that by use of efficient scheduling and resource allocation techniques significant savings in terms of consumed energy can be achieved, without compromising QoS.

In this paper, we analyze by theoretical calculation of the proposed scheme for collision detection in wireless local area networks (WLANs). The proposed scheme utilizes the medium access control (MAC) procedure of multiple input multiple output (MIMO) transmission technology, which is used to achieve high-speed transmission in WLANs in recent years; however, the transmission efficiency degrades at the MAC layer level, although a high transmission link rate is achieved at the physical (PHY) layer. The proposed scheme were performed high transmission efficiency of approximately 90% by the computer simulation in our previous work. In this paper, the results of our theoretical calculations correspond with the computer simulation results, indicating that the proposed scheme is indeed efficient and reliable.

Multiple-input multiple-output (MIMO) signaling is one of the key technologies of current mobile communication systems. However, the complex and expensive radio frequency (RF) chains have always limited the increase of MIMO scale. In this paper, we propose a MIMO transmission architecture based on a dual-polarized reconfigurable intelligent surface (RIS), which can directly achieve modulation and transmission of multichannel signals without the need for conventional RF chains. Compared with previous works, the proposed architecture can improve the integration of RIS-based transmission systems. A prototype of the dual-polarized RIS-based MIMO transmission system is built and the experimental results confirm the feasibility of the proposed architecture. The dual-polarized RIS-based MIMO transmission architecture provides a promising solution for realizing low-cost ultra-massive MIMO towards future networks.

Multiple-input multiple-output (MIMO) systems are threatened by smart attackers, who apply programmable radio devices such as software defined radios to perform multiple types of attacks such as eavesdropping, jamming and spoofing. In this paper, MIMO transmission in the presence of smart attacks is formulated as a noncooperative game, in which a MIMO transmitter chooses its transmit power level and a smart attacker determines its attack type accordingly. A Nash equilibrium of this secure MIMO transmission game is derived and conditions assuring its existence are provided to reveal the impact of the number of antennas and the costs of the attacker to launch each type of attack. A power control strategy based on Q-learning is proposed for the MIMO transmitter to suppress the attack motivation of smart attackers in a dynamic version of MIMO transmission game without being aware of the attack and the radio channel model. Simulation results show that our proposed scheme can reduce the attack rate of smart attackers and improve the secrecy capacity compared with the benchmark strategy.

The radio over fiber (RoF)-distributed antenna system (DAS) over a wavelength division multiplexing-passive optical network (WDM-PON) with multiple input multiple output (MIMO) employing bandpass-sampling and optical time division multiplexing (TDM) techniques has been proposed to realize next generation broadband wireless access with higher throughput and its preliminary feasibility has been confirmed. To investigate the performance of bandpass-sampled and time domain multiplexed optical signals, and enhance the transmission performance in the wireless link of the RoF-DAS over WDM-PON, we perform two-tone signal transmission experiments with 2.4 GHz band radio frequency (RF) signals and analyze the RF carrier power, third-order intermodulation distortion (IMD) power and noise power. The analysis results confirmed that the nonlinearity of the proposed system is mainly caused by a lithium niobate-Mach-Zehnder modulator (LN-MZM) as with the other RoF systems and that the dominant noise components are the signal-spontaneous beat noise arising from the amplified spontaneous emission (ASE) of two erbium doped fiber amplifiers (EDFAs) and the signal-signal beat noise caused by the interference between the optical TDM pulses. The latter is the specific noise component in the proposed system. In addition, we clarify the principle of the signal-signal beat noise generation and report that the signal-spontaneous beat noise can be reduced by the gain optimization of the two EDFAs.

Distributed antenna systems (DASs) have been proposed for use in high-data-rate wireless communications. Connecting the central unit to remote antenna units, radio over fiber (RoF) links become essential parts of the DAS. One of the major problems in the RoF links is the nonlinear distortion experienced in its optoelectronic devices. This paper considers the adaptive compensation of the nonlinear RoF link. In particular, we present an extension to the conventional least-mean-square algorithm for memory-polynomial-based predistortion. In addition, we study different combinations of the algorithms for the predistortion. Moreover, we implement the adaptive predistorter in hardware, build a real RoF link, and verify the performance by measurements. The results demonstrate that distortion of the RoF link can be considerably diminished with a low complexity design.

An approach to predict the throughput of multiple-input multiple-output (MIMO) transmission systems in radio network planning tools is proposed in this paper. Two different measurement campaigns have been evaluated. At first the Shannon MIMO transmission capacity is calculated based on MIMO channel sounder measurements. At second LTE throughput measurements in a field trial network with specific network configurations have been investigated. Both campaigns were located in urban areas and a 2×2 MIMO system with cross-polarised antennas was used. The MIMO capacity gain is derived from both investigations and it is shown that it is correlated with the difference between the free space path loss and the experienced path loss. This measure is the basis of the suggested approach. It includes the length as well as the land usage of the radio path and it requires only input data which is generally available from macro cell propagation models.

In this paper, a new multiple-input multiple-output (MIMO) transmission technique, which is called double spatial modulation (DSM), is proposed as a new high-rate generalized spatial modulation (SM) scheme. DSM scheme aims to improve the spectral efficiency of classical SM by increasing the number of active transmit antennas. In the DSM scheme, incoming data bits determine two modulated symbols as well as their corresponding activated transmit antenna indices. One of the modulated symbols is directly transmitted over its corresponding activated transmit antenna, while the other one is transmitted with a rotation angle, which is optimized for M-ary quadrature amplitude modulation (M-QAM) signal constellation, over the second activated transmit antenna. The error performance of the proposed DSM scheme is compared with the recently proposed emerging SM schemes such as quadrature SM (QSM) and enhanced SM (ESM). Our computer simulations show that the DSM scheme provides considerably better error performance than QSM and ESM schemes for different spectral efficiency values. In addition, the pairwise error probability (PEP) of DSM is derived and the average bit error probability (ABEP) over uncorrelated Rayleigh fading channels is obtained for different M-QAM constellations.

Visible Light Communication (VLC) has emerged as a powerful technique for wireless communication systems. Providing high data rate and increasing capacity are the major problems in VLC. Recent evidence suggests that Multiple Input Multiple Output (MIMO) technique can offers improved data rates and increased link range. This paper describes the design and implementation of visible light communication system in indoor environment exploring the benefits of MIMO. The specific objective of this research was to implement a 4×4 Multiple Input (LEDs) Multiple Output (photodetectors)-VLC communication system, where a 16 white power LEDs in four arrays are setting up at transmitter and four RX modules are setting up at receiver side without the need for additional power or bandwidth as well as analyze a mathematical model for a VLC- 4×4 MIMO with different modes such as the suitable angles to cover the entire room. The research designs practically an electronic circuit for the transmitter and receiver with inexpensive components. The power distribution of different propagation modes is calculated for Single Input Single Output (SISO) and MIMO channels in typical room dimensions. The results in this paper indicate that the power is distributed uniformly for entire room when implemented VLC-MIMO as compared to VLC-SISO. Furthermore, a 4×4 MIMO implementing VLC is compared in term of BER vs. SINR with SISO communication system for both Line of Sight (LOS) and Non Line of Sight (NLOS) propagation modes. Comparing the two results of LOS and NLOS, it can be seen that a 4×4 MIMO implementing VLC for LOS perform better than the same system with NLOS due to decreasing in the received power resulted from the multipath effect.