Transceiver Design for GFDM with Index Modulation in Multi-user Networks

Index modulation (IM) techniques can be applied to the different media in order to achieve spectral- and energyefficient communication as well as to the indices of the subcarriers of a generalized frequency division multiplexing (GFDM) data block. In this work, a novel transceiver architecture for multiuser GFDM-IM system is introduced. The performance of the GFDM-IM is studied by considering the bit error rate (BER) as performance metric. It is shown that better BER performance than the classical GFDM and the orthogonal frequency division multiplexing (OFDM) with IM can be achieved by employing IM to the GFDM

Index Modulation Techniques for Energy-efficient Transmission in Large-scale MIMO Systems

This thesis exploits index modulation techniques to design energy- and spectrum-efficient system models to operate in future wireless networks. In this respect, index modulation techniques are studied considering two different media: mapping the information onto the frequency indices of multicarrier systems, and onto the antenna array indices of a platform that comprises multiple antennas. The index modulation techniques in wideband communication scenarios considering orthogonal and generalized frequency division multiplexing systems are studied first. Single cell multiuser networks are considered while developing the system models that exploit the index modulation on the subcarriers of the multicarrier systems. Instead of actively modulating all the subcarriers, a subset is selected according to the index modulation bits. As a result, there are subcarriers that remain idle during the data transmission phase and the activation pattern of the subcarriers convey additional information. The transceivers for the orthogonal and generalized frequency division multiplexing systems with index modulation are both designed considering the uplink and downlink transmission phases with a linear combiner and precoder in order to reduce the system complexity. In the developed system models, channel state information is required only at the base station. The linear combiner is designed adopting minimum mean square error method to mitigate the inter-user-interference. The proposed system models offer a flexible design as the parameters are independent of each other. The parameters can be adjusted to design the system in favor of the energy efficiency, spectrum efficiency, peak-to-average power ratio, or error performance. Then, the index modulation techniques are studied for large-scale multiple-input multiple-output systems that operate in millimeter wave bands. In order to overcome the drawbacks of transmission in millimeter wave frequencies, channel properties should be taken in to account while envisaging the wireless communication network. The large-scale multiple-input multiple-output systems increase the degrees of freedom in the spatial domain. This feature can be exploited to focus the transmit power directly onto the intended receiver terminal to cope with the severe path-loss. However, scaling up the number of hardware elements results in excessive power consumption. Hybrid architectures provide a remedy by shifting a part of the signal processing to the analog domain. In this way, the number of bulky and high power consuming hardware elements can be reduced. However, there will be a performance degradation as a consequence of renouncing the fully digital signal processing. Index modulation techniques can be combined with the hybrid system architecture to compensate the loss in spectrum efficiency to further increase the data rates. A user terminal architecture is designed that employs analog beamforming together with spatial modulation where a part of the information bits is mapped onto the indices of the antenna arrays. The system is comprised a switching stage that allocates the user terminal antennas on the phase shifter groups to minimize the spatial correlation, and a phase shifting stage that maximizes the beamforming gain to combat the path-loss. A computationally efficient optimization algorithm is developed to configure the system. The flexibility of the architecture enables optimization of the hybrid transceiver at any signal-to-noise ratio values. A base station is designed in which hybrid beamforming together with spatial modulation is employed. The analog beamformer is designed to point the transmit beam only in the direction of the intended user terminal to mitigate leakage of the transmit power to other directions. The analog beamformer to transmit the signal is chosen based on the spatial modulation bits. The digital precoder is designed to eliminate the inter-user-interference by exploiting the zero-forcing method. The base station computes the hybrid beamformers and the digital combiners, and only feeds back the digital combiners of each antenna array-user pair to the related user terminals. Thus, a low complexity user architecture is sufficient to achieve a higher performance. The developed optimization framework for the energy efficiency jointly optimizes the number of served users and the total transmit power by utilizing the derived upper bound of the achievable rate. The proposed transceiver architectures provide a more energy-efficient system model compared to the hybrid systems in which the spatial modulation technique is not exploited. This thesis develops low-complexity system models that operate in narrowband and wideband channel environments to meet the energy and spectrum efficiency demands of future wireless networks. It is corroborated in the thesis that adopting index modulation techniques both in the systems improves the system performance in various aspects.:1 Introduction 1 1.1 Motivation 1 1.2 Overview and Contribution 2 1.3 Outline 9 2 Preliminaries and Fundamentals 13 2.1 Multicarrier Systems 13 2.2 Large-scale Multiple Input Multiple Output Systems 17 2.3 Index Modulation Techniques 19 2.4 Single Cell Multiuser Networks 22 3 Multicarrier Systems with Index Modulation 27 3.1 Orthogonal Frequency Division Multiplexing 28 3.2 Generalized Frequency Division Multiplexing 40 3.3 Summary 52 4 Hybrid Beamforming with Spatial Modulation 55 4.1 Uplink Transmission 56 4.2 Downlink Transmission 74 4.3 Summary 106 5 Conclusion and Outlook 109 5.1 Conclusion 109 5.2 Outlook 111 A Quantization Error Derivations 113 B On the Achievable Rate of Gaussian Mixtures 115 B.1 The Conditional Density Function 115 B.2 Tight Bounds on the Differential Entropy 116 B.3 A Bound on the Achievable Rate 118 C Multiuser MIMO Downlink without Spatial Modulation 121 Bibliograph

Orthogonal Generalized Frequency Division Multiplexing (OGFDM)

This thesis focuses on introducing a novel technique of the transmission waveform termed as orthogonal generalized frequency division multiplexing (OGFDM) for increasing the wireless channel capacity without the need for extra bandwidth (BW) size or power consumption. The new wireless waveform (OGFDM) tends to obtain a better BW efficiency which in turn can increase highly the wireless channel capacity in comparison with the generalized frequency division multiplexing (GFDM) and cyclic-prefix orthogonal frequency division multiplexing (CP-OFDM). The main feature of the OGFDM is developing the physical layer of future mobile networks by achieving the orthogonality between non-orthogonal filters, removing the interference between adjacent frequency subcarriers, and gaining a flexible bit loading scheme. Since the key downsides of the 4G waveform (CP-OFDM), several alternative transmission waveforms have been investigated for improving transmission techniques of the upcoming communication networks (5G and beyond). This, as a result, comes up with introducing the GFDM as the best candidate waveform for the 5G air interface. Nevertheless, due to ignoring the orthogonality with the GFDM, the BW efficiency is severely affected which in turn causes in extremely reducing the gained channel capacity (research gap). For this reason, the proposed OGFDM waveform aims to improve wireless channel capacity by investigating different levels of processing and carrier schemes. As such, three key levels called as filtration level, oversampling level, and modulation level are adopted for a variant range of OGFDM carriers like a single carrier, couple carrier, quadruple carrier, and multi-carrier system. Regarding the single carrier OGFDM system where the filtration level is developed, the orthogonality is attained between the non-orthogonal filters of the GFDM frequency subcarriers. The core idea behind this novel technique is increasing the efficiency of the applied BW which in turn can double the capacity of the channel at the acceptable level of the bit error rate (BER). Concerning the couple carrier OGFDM system where the oversampling level is developed, the double oversampling mode is applied side by side with the normal one. As a result, the OGFDM waveform can efficiently avoid the interference between adjacent frequency subcarriers improving the quality of service under bad transmission states. As regards the quadruple carrier OGFDM system where the modulation level is improved, a flexible modulation scheme is utilized rather than the fixed modulation formats. Consequently, multilevel modulation shapes are optimally assigned to gain an enhanced channel capacity in accordance with the realistic transmission state. To achieve a higher BW efficiency, the preliminary multi-carrier system that combines the three levels of processing in one uniformed physical platform is introduced. To demonstrate the main advantages of OGFDM waveform, the multicarrier system is further extended and compared with the GFDM (5G technology) and CP-OFDM (LTE Ericsson technology). Hence, the multi-carrier OGFDM can double, boost, and yet maximize the bit-rate of the transmission relative to the GFDM and CP-OFDM at the acceptable level of the BER. The MATLAB simulation and Visio tools are utilized to validate the results and represent them graphically