Multidimensional Index Modulation for 5G and Beyond Wireless Networks

This study examines the flexible utilization of existing IM techniques in a comprehensive manner to satisfy the challenging and diverse requirements of 5G and beyond services. After spatial modulation (SM), which transmits information bits through antenna indices, application of IM to orthogonal frequency division multiplexing (OFDM) subcarriers has opened the door for the extension of IM into different dimensions, such as radio frequency (RF) mirrors, time slots, codes, and dispersion matrices. Recent studies have introduced the concept of multidimensional IM by various combinations of one-dimensional IM techniques to provide higher spectral efficiency (SE) and better bit error rate (BER) performance at the expense of higher transmitter (Tx) and receiver (Rx) complexity. Despite the ongoing research on the design of new IM techniques and their implementation challenges, proper use of the available IM techniques to address different requirements of 5G and beyond networks is an open research area in the literature. For this reason, we first provide the dimensional-based categorization of available IM domains and review the existing IM types regarding this categorization. Then, we develop a framework that investigates the efficient utilization of these techniques and establishes a link between the IM schemes and 5G services, namely enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communication (URLLC). Additionally, this work defines key performance indicators (KPIs) to quantify the advantages and disadvantages of IM techniques in time, frequency, space, and code dimensions. Finally, future recommendations are given regarding the design of flexible IM-based communication systems for 5G and beyond wireless networks.Comment: This work has been submitted to Proceedings of the IEEE for possible publicatio

A Study on Three Dimensional Spatial Scattering Modulation Systems

With an explosive growth of data traffic demand, the researchers of the mobile communication era forecast that the traffic volume will have a 1000x increase in the forthcoming beyond fifth generation (B5G) network. To satisfy the growing traffic demand, the three-dimensional (3-D) multiple-input-and-multiple-output (MIMO) system is considered as a key technology to enhance spectrum efficiency (SE), which explores degrees of freedom in both the vertical and the horizontal dimensions. Combined with 3-D MIMO technology, index modulation (IM) is proposed to improve both energy efficiency (EE) and SE in the B5G era. Existing IM technologies can be categorized according to the domain in which the additional IM bits are modulated, e.g., the spatial-domain IM, the frequency-domain IM and the beamspace-domain IM etc. As one of the mainstream IM techniques, spatial scattering modulation (SSM) is proposed, which works in the beamspace-domain. For SSM systems, the information bits are denoted by the distinguishable signal scattering paths and the modulated symbols. Therein, two information bit streams are transmitted simultaneously by selections of modulated symbols and scattering paths. However, the existing papers only discuss two-dimensional (2-D) SSM systems. The 2-D SSM system applies linear antenna arrays, which only take the azimuth angles to recognise the direction of scattering paths. Therefore, to take the full advantage of the beamspace-domain resources, this thesis mainly focuses on the 3-D SSM system design and the performance evaluation. Firstly, a novel 3-D SSM system is designed. For the 3-D SSM system, besides the azimuth angles of arrival (AoA) and angles of departure (AoD), the elevation AoA and AoD are considered. Then the optimum detection algorithm is obtained, and the closed-form union upper bound expression on average bit error probability (ABEP) is derived. Moreover, the system performance is evaluated under a typical indoor environment. Numerical results indicate that the novel 3-D SSM system outperforms the conventional 2-D SSM system, which reduces the ABEP by 10 times with the same signal-to-noise ratio (SNR) level under the typical indoor environment. Secondly, for the system equipped with large-scale antenna arrays, hybrid beamforming schemes with several RF-chains have attracted more attention. To further explore the throughput of the 3-D SSM system, a generalised 3-D SSM system is proposed, which generates several RF-chains in a transmission time slot to convey modulated symbols. A system model of generalised 3-D SSM is proposed at first. Then an optimum detection algorithm is designed. Meanwhile, a closed-form expression of the ABEP is also derived and validated by Monte-Carlo simulation. For the performance evaluation, three stochastic propagation environments with randomly distributed scatterers are adopted. The results reveal that the generalised 3-D SSM system has better ABEP performance compared with the system with a single RF-chain. Considering different propagation environments, the SSM system has better ABEP performance under the statical propagation environments than the stochastic propagation environments. Thirdly, to reduce the hardware and computational complexities, two optimisation schemes are proposed for the generalised 3-D SSM systems. The 2-D fast Fourier transform (FFT) based transceivers are designed to improve the hardware friendliness, which replace the analogue phase shift networks by the multi-bit phase shifter networks. To reduce the computational complexity of the optimum detection algorithm, a low-complexity detection scheme is designed based on the linear minimum mean square error (MMSE) algorithm. Meanwhile, to quickly evaluate, the asymptotic ABEP performance and the diversity gain of the generalised 3-D SSM system are obtained

Millimeter Wave MIMO-OFDM with Index Modulation: A Pareto Paradigm on Spectral- Energy Efficiency Trade-Off

Multiple-input multiple-output orthogonal frequency division multiplexing with index modulation (MIMO-OFDM-IM) has recently received increased attention, due to the potential advantage to balance the trade-off between spectral efficiency (SE) and energy efficiency (EE). In this paper, we investigate the application of MIMO-OFDM-IM to millimeter wave (mmWave) communication systems, where a hybrid analogy-digital (HAD) beamforming architecture is employed. Taking advantage of the Pareto-optimal beam design, we propose a feasible solution to approximately achieve a globally Pareto-optimal trade-off between SE and EE, and the collision constraints of the multi-objective optimization problem (MOP) can be solved efficiently. Correspondingly, the MOP of SE-EE trade-off can be converted into a feasible solution for energy-efficient resource usage, by finding the Pareto-optimal set (POS) towards the Pareto front. This combinatorial-oriented resource allocation approach on the SE-EE relation considers the optimal beam design and power control strategies for downlink multi-user mmWave transmission. To ease the system performance evaluation, we adopt the Poisson point process (PPP) to model the mobile data traffic, and the evolutionary algorithm is applied to speed up the search efficiency of the Pareto front. Compared with benchmarks, the experimental results collected from extensive simulations demonstrate that the proposed optimization approach is vastly superior to existing algorithms

Performance investigation of spatial modulation systems under realistic channel models

In order to fulfil the explosive demand for convenient wireless data access, novel wireless technologies such as the multiple-input-multiple-output (MIMO) have widely been used to improve the link reliability and capacity of wireless communication systems. In recent years, a new MIMO technology named the spatial modulation (SM) has attracted signi cant research interest due to its reported enhancement on the system performance with the reasonable system complexity. Before a new technology comes into real use, it is necessary to comprehensively evaluate its performance under different scenarios. In this thesis, we investigate the performance of SM systems under some important realistic scenarios for future wireless communications, such as the vehicle-to-vehicle (V2V), the high-speed train (HST), and the massive MIMO scenarios. Firstly, the bit error rate (BER) performance of SM systems under a novel threedimensional (3D) geometry based stochastic model (GBSM) for V2V MIMO channels is investigated by both theoretical analysis and system simulations. The impacts of vehicle tra c density (VTD), Doppler effect, and 3D feature on the BER performance of SM systems are thoroughly studied. In addition, other MIMO technologies, such as the vertical Bell Labs layered space-time (V-BLAST), the Alamouti scheme are compared with SM under different simulation settings. Secondly, the BER performance of SM systems is studied under a non-stationary wideband HST GBSM considering the non-ideal channel estimation case. The timevarying behaviour of the channel and its impact on the performance of SM systems are comprehensively investigated. The accurate theoretical BER expression of SM systems under a non-stationary wideband HST channels with non-ideal channel estimation is derived. A novel statistic property named stationary interval in terms of the space-time correlation function (STCF) is introduced in order to clearly explain all theoretical and simulation results. Thirdly, the performance of SM systems is evaluated under a Kroneck-based massive MIMO channel model. As a massive MIMO system employs large numbers of antennas, antenna elements are distributed over a wide range. Thus, different antenna elements may observe different sets of clusters. How this phenomenon affects the performance of SM systems is investigated by considering a survival probability of clusters, which abstracts the birth-death process of each cluster in the channel model. Moreover, the performance of SM systems is also compared with that of other MIMO technologies under the massive MIMO channel model. In summary, all research works in this thesis have considered realistic MIMO channel models, which are meaningful for the test, performance evaluation, and implementation of SM technology for future advanced wireless communications systems

On the energy efficiency of spatial modulation concepts

Spatial Modulation (SM) is a Multiple-Input Multiple-Output (MIMO) transmission technique which realizes low complexity implementations in wireless communication systems. Due the transmission principle of SM, only one Radio Frequency (RF) chain is required in the transmitter. Therefore, the complexity of the transmitter is lower compared to the complexity of traditional MIMO schemes, such as Spatial MultipleXing (SMX). In addition, because of the single RF chain configuration of SM, only one Power Amplifier (PA) is required in the transmitter. Hence, SM has the potential to exhibit significant Energy Efficiency (EE) benefits. At the receiver side, due to the SM transmission mechanism, detection is conducted using a low complexity (single stream) Maximum Likelihood (ML) detector. However, despite the use of a single stream detector, SM achieves a multiplexing gain. A point-to-point closed-loop variant of SM is receive space modulation. In receive space modulation, the concept of SMis extended at the receiver side, using linear precoding with Channel State Information at the Transmitter (CSIT). Even though receive space modulation does not preserve the single RF chain configuration of SM, due to the deployed linear precoding, it can be efficiently incorporated in a Space Division Multiple Access (SDMA) or in a Virtual Multiple-Input Multiple-Output (VMIMO) architecture. Inspired by the potentials of SM, the objectives of this thesis are the evaluation of the EE of SM and its extension in different forms of MIMO communication. In particular, a realistic power model for the power consumption of a Base Station (BS) is deployed in order to assess the EE of SM in terms of Mbps/J. By taking into account the whole power supply of a BS and considering a Time Division Multiple Access (TDMA) multiple access scheme, it is shown that SM is significantly more energy efficient compared to the traditional MIMO techniques. In the considered system setup, it is shown that SM is up to 67% more energy efficient compared to the benchmark systems. In addition, the concept of space modulation is researched at the receiver side. Specifically, based on the union bound technique, a framework for the evaluation of the Average Bit Error Probability (ABEP), diversity order, and coding gain of receive space modulation is developed. Because receive space modulation deploys linear precoding with CSIT, two new precoding methods which utilize imperfect CSIT are proposed. Furthermore, in this thesis, receive space modulation is incorporated in the broadcast channel. The derivation of the theoretical ABEP, diversity order, and coding gain of the new broadcast scheme is provided. It is concluded that receive space modulation is able to outperform the corresponding traditional MIMO scheme. Finally, SM, receive space modulation, and relaying are combined in order to form a novel virtual MIMO architecture. It is shown that the new architecture practically eliminates or reduces the problem of the inefficient relaying of the uncoordinated virtual MIMO space modulation architectures. This is undertaken by using precoding in a novel fashion. The evaluation of the new architecture is conducted using simulation and theoretical results

Mm-Wave STSK-aided single carrier block transmission for broadband networking

Millimeter wave (mm-Wave) communications has been considered as a strong candidate for future wireless standards, due to the large available bandwidth in the order of gigahertz. As a result, a plethora of future services and application-oriented scenarios can be conceived, under suitable propagation conditions. Accurate physical (PHY) layer design plays a vital role in the deployment of robust transmission systems able to efficiently exploit the large bandwidth portions available in the mm-Wave frequencies. In this paper, we propose Space-Time Shift Keying (STSK) MIMO coding combined with Cyclic-Prefixed Single Carrier (CP-SC) block transmission for broadband data exchange over frequency-selective mm-Wave channels. STSK allows to exploit transmit and receive diversity with better performance when compared with state-of-the-art MIMO techniques only relying on receive diversity, such as, for example Spatial Modulation (SM). The performance of CP-SC-STSK and CP-SC-SM have been assessed in the presence of phase noise and imperfect channel estimation, considering 2 and 4 elements MIMO systems and LoS indoor vs. nLoS outdoor 73 GHz multipath channels. We show that the STSK-based solution using MMSE Frequency-Domain Equalization (FDE) is very robust against the aforementioned impairments and clearly outperforms CP-SC-SM at the price of a slight increase of receiver complexity and a throughput reduction of 50% when 4 × 4 MIMO systems are considered