Multiple-input multiple-output (MIMO) techniques are the fundamental technology in several standardizations, including long-term evolution (LTE) and LTE-advanced. For instance, MIMO spatial multiplexing (MIMO-SM) is used to increase the system capacity without requiring additional time/frequency resources. However, the performance of the MIMO-SM depends on the employed detection algorithm. Also, multi-user MIMO precoding at the transmitter part is used to support the simultaneous transmission to several users. In this book, we review the basics of MIMO detection. Then, we introduce two detection algorithms, namely, adaptive parallel QRDM algorithm (APQRDM) that increases the detection throughput and adaptive iterative QRD-M algorithm (AIQRDM) that reduces the hardware requirements. Besides, these two algorithms adaptively reduce the computational complexity, while achieving the optimum diversity. Furthermore, in addition to introducing the state of the art of the precoding techniques, we propose a fixed complexity sphere encoder (FSE) that requires a fraction of the computations performed by the QRDM encoder, while achieving a tremendous increase in the precoding throughput.
Wireless communication is an emerging field, which has seen enormous growth in the last several years. Wireless Networks and the exponential growth of the internet have resulted in an increased demand for new methods of obtaining robust, high capacity wireless networks. In this book, we have mainly focused on various methods for improving the spectral efficiency and link reliability of Wireless network using MIMO-OFDM system, and also observing the bandwidth efficiency with the varying length of cyclic prefix. We have also focused on different detection algorithms required in the reception of MIMO-OFDM signals, which have recently emerged as a very promising approach to solve detection problem.
Multiple input multiple output (MIMO) wireless systems that use multiple transmit and receive antennas allow a gain in reliability (diversity gain) and capacity (multiplexing gain). Unfortunately, these advantages come at the cost of higher computational complexity, particularly when using soft detection (SD). SD features improved performance compared to hard detection and is a prerequisite for iterative receiver structures (turbo receivers). In this thesis we consider the sphere decoder for soft-output MIMO detection and present modifications that allow flexible trade-offs between computational complexity on the one hand and performance and diversity on the other hand. Additionally to these two modifications we present a lower bound on partial sphere decoder metrics that allows to reduce the complexity of the detection using the sphere decoder without performance degradation.
This book investigates the problem of user selection and scheduling in MIMO-BC. A low-complexity user selection algorithm is proposed when the BS has perfect channel-state information and the performance of the proposed algorithm with linear and non-linear precoding techniques is evaluated. A signalling scheme for the MIMO-BC systems in the absence of perfect CSIT is presented. A novel transmit-antenna selection scheme is proposed. The performance of the proposed scheme with different user selection algorithms and linear receivers is evaluated. The book considers a cross-layer scheduling approach in order to provide QoS guarantees to the users. A scheduling algorithm, multi-user ?-Rule scheduling, is proposed with the capability of maximizing the system throughput and providing QoS to the users. The effect of rate estimation on the performance of the scheduling algorithm is analyzed along with the effect of the variability in the allocated rates on the mean queue lengths of the users. It is shown that by increasing the fairness, the variability in rate allocation decreases, which results in smaller queue sizes for the users with marginal reduction in the sum-capacity of the system.
This book presents a general overview on the concept of MIMO OFDM for communication systems. Moreover, the different detection schemes for such systems are portrayed with special emphasis on the LS, ZF & LMMSE detector. The core of a LMMSE detector requires matrix inversion, which is usually regarded as a computationally intensive task. Hence, the CORDIC and SGR algorithms that can be used to decrease the complexity of matrix inversion are explored in depth and their software and hardware implementation issues are analyzed. The goal of this thesis is to realize an implementation of the LMMSE detector on an FPGA, since results from hardware simulations are faster and more valuable to designers compared to software based simulations.
The prime objectives in the development of Next Generation Wireless Communication systems are to increase the link throughput and network capacity. These demands translate into designing systems that have improved spectral efficiency, efficient bandwidth utilization, computationally economical signal processing algorithms and high speed processing hardware. The available frequency spectrum is limited and a very scarce resource. Hence, efficient channel utilization techniques are required to exploit the channel conditions more proficiently. MIMO technology has become popular in wireless communication systems to achieve enhanced spectral efficiency in rich scattering environments. Test-beds are requisite to validate the results of theory and simulations. The focal benefit of a test-bed is the leeway to study and compare different synchronization, channel estimation and detection algorithms in realistic environments. One of the aspirations of this research work is to achieve real-time video transmission over Next Generation Wireless Systems employing MIMO transmission which enables enhanced data rates utilizing the same frequency band.
Base station cooperation (BSC), also known as Cooperative Multi-Point (CoMP), has been identified as a key radio access technology for next-generation cellular networks. This work creates a foundational framework that extends BSC transmission to provide spatial spectrum sharing (SSS) through MIMO null beamforming while enjoying cooperative stream transmission. SSS is investigated by introducing the protected Gaussian MIMO broadcast channel (PGMBC), a GMBC with receive power constraints. Applications of the PGMBC are identified and its capacity region is derived. In addition, precoding schemes are developed to mitigate intercell interference and intersystem interference. The simulations show that through BSC, significant throughput gains over non-cooperative null-beamforming schemes can be achieved. However, to maximize the benefits of BSC in practical networks, the location and configuration of BS sites must be planned accordingly. This work introduces a fundamental framework for planning BSC networks. The impacts of BSC on coverage, capacity, complexity are investigated. In addition, a cell planning procedure for distributed, dynamic fractional BSC networks is described.
With the evolution in the telecommunication generations, more and more research is going on in the field of wireless communications. The purpose of these researches has always been to provide good network coverage across the region with higher data rates, accuracy and better performance. Control on coverage and performance has always been in focus and is achieved by using better and better antennas. The research in this thesis is also based upon these main factors.
MIMO systems using multiple transmitting and receiving antennas are by now well studied. Several axes of these schemes have been explored with the underlying MIMO channel assumed linear. However, when high-power amplifiers (HPA) operating near their peak efficiency operating points are employed in the communication chain, non-linear distortions are introduced in the transmitted signals, and the resulting MIMO channel will be non-linear. This book establishes the concept of Nonlinear MIMO communication channels. The book begins by examining the performance degradations caused by HPA nonlinearities in MIMO channels, using space-time codes and MIMO-beamforming systems as case studies. The book then concludes by highlighting some key HPA nonlinearity compensation techniques suitable for MIMO systems.
The growing miniaturization of electronic devices combined with the recent developments in wearable computer technology have been leading to the creation of a wide range of devices which can be carried in a pocket or attached to a user’s body. These applications have allowed the removal of the need for wired interconnections and have led to the rise of the concept of the wireless body area network (WBAN). These networks have a wide range of applications such as healthcare, smart home, monitoring, mobile entertainment, etc. To ensure the efficient performance of such wireless networks the radio propagation channels and the antenna systems need to be characterized and modeled. This study focuses on the characterization of the channel of WBANs and on the design of a body worn antenna. To face the fading generated by the body movement, a MIMO antenna has been designed exploiting the Theory of the Characteristic Modes. This research covers several topics and should be especially useful to professionals in Communication Technologies or anyone else who wants to increase knowledge in on body wireless networks and MIMO multimode antennas.
Due to its increasing applications in personal communications systems, body-centric wireless communications has become a major field of interest for researchers. Fading and interference are the two concerns that affect the reliability and quality of service of wireless links. Diversity has been used to overcome these two problems. This book looks into the use of receive diversity for on-body channels. Space, pattern, and polarization diversity performance is analyzed and quantified by actual measurements in real environments. The on-body diversity channels have also been characterized by performing the statistical and spectral analyses. Diversity has been found effective in the BAN-BAN interference rejection and significant rejection gain values are achieved. A new algorithm for BAN- BAN interference rejection has been proposed and compared with the conventional adaptive algorithms. The use of multiple antennas at both the transmitter and receiver end, i.e., MIMO has been investigated for on-body applications. It has been noticed that MIMO provides significant capacity increase for these channels despite the line-of-sight.
In this work, Survey and investigation on inter symbol interference (ISI) and inter carrier interference (ICI) due to either carrier frequency offset or timing offset issues and interference mitigation schemes available, compare and analyze their bit error rate performance to various schemes for OFDM and MIMO-OFDM systems. Efforts have been made to develop an efficient interference cancelling receiver for ISI and ICI, algorithms to be implemented on MATLAB environment for OFDM and MIMO-OFDM which are not available in literature.
We have tried to describe two aspects of MIMO channels: channel capacity and channel modeling. We have analyzed the channel capacity of static and fading MIMO channels when the channel side information is available both at the transmitter and receiver, and when it is available only at the receiver. We have then modeled the MIMO channel in physical and angular domains to understand how it provides spatial multiplexing with the help of degrees of freedom. In physical domain modeling, we have modeled the MIMO channel in terms of individual physical paths. In angular domain modeling, we have described the MIMO channel with respect to fixed spatial basis functions defined by fixed angles that are determined by the spatial resolution of the antenna arrays. All the simulations have been performed on MATLAB 22.214.171.1247 (R2007a).
The effects of sub-channel packet routing and adaptive modulation (AM) are discussed in this book for MIMO linking system under differing channel conditions. The challenges is to exploit time-varying imbalances between logical sub-channels by different cross-layer routing and modulation strategies to improve overall goodput. MIMO sub-channels are modelled using OMNeT++ to form a single protocol link and then extended into the final interesting quad- parallel independent link model (Quad-PILM) to explore the effect of channel BER imbalance by implementing frame-by-frame sub-channel re-routing and retry mechanism with the aim of improving overall goodput. As a final model, a BER-directed adaptive modulation switching scheme is evaluated. The explanation in this book demonstrates that even quite simple switching heuristics and packet re-routing mechanisms can provide an overall improvement in a common real-world situation where MIMO sub-channels exhibit slightly unequal error rates for durations of one or more transmission frames.
The basic of multiple hops MIMO relay system is described from ideal channel models to the real channel model, from one-way transmissions to two-ways transmissions. Both amplify-and-forward and decode-and-forward schemes are respectively analyzed based on MAC layer, PHY layer and then MAC-PHY cross layer. The idea and the mathematical derivation are depicted clearly. Additionally, conventional schemes, e.g. CSMA/CA, network coding, cooperative relaying and so on, are introduced and compared to the proposed MAC-PHY cross layer.
This book presents reduced complexity and proportional data rate fairness resource allocation schemes for next generation broadband mobile wireless communication systems. At first we present proportional data rate fairness resource allocation scheme for Multi-Input Multi-Output Orthogonal Frequency Division Multiple Access (MIMO- OFDMA) broadband mobile wireless communication system. In this scheme, users are separated in frequency domain and they cannot transmit their data in same frequency with other users at the same time. Therefore, second resource allocation considers to use the radio frequency spectrum more efficiently by using same frequency to transmit for different user’s data at the same time in the system. Therefore, we can use scarce spectral resources more efficiently in the MIMO-OFDM wireless communication system environments under the consideration of proportional data rate fairness constraint and QoS requirements among users in the system. Reduced complexity antenna selection method for practical MIMO communication system is also presented based on Singular value decomposition (SVD) and polarization effect in the wireless communication system.