In this book, novel and improved techniques are proposed for the simulation and performanceevaluation of MIMO wireless communication systems in the presence of imperfect channel state information (CSI). priori knowledge of this parameter is very advantageous to the analysisand system performance in term of a higher quality bit error rate (BER) and improved data rate(bits/sec). Both advantages can be used to increase the channel’s quality of service and throughputsignificantly. First, the performance of the Alamouti Space Time Code (STC) in a time varyingRayleigh fading channel in the presence of imperfect CSI is presented. Next, a model for a mobile tomobile MIMO communication link is proposed. An analytical expression for the achievable rates and optimal frame lengths in channels with pilot assistedestimation for a given quality of estimation is derived. Also, an optimization of the pilot symbol spacing to maximize the spectrum efficiency using an adaptive M-PSK modulation technique is proposed. A number of applications is presented to show how their performance could be evaluated using the proposed model and techniques.
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 new generation of wireless devices support higher data rates. Most of the new standards like HSPA utilize the spatial multiplexing of MIMO channels to achieve higher data rates, and exploit the diversity of MIMO channels to provide better performance. Hence there is an increased interest in the analysis of MIMO communication systems. The eventual objective is to achieve higher data rates in MIMO systems under the constraints of limited bandwidth and power. The radio spectrum is a scarce resource, and very expensive to license. Hence improved and efficient channel utilization techniques are requisite, that exploit the radio spectrum more proficiently. The multipath characteristics of the environment cause the MIMO channels to be frequency selective. For frequency selective deep fading, MIMO system remains ineffective. OFDM, a multicarrier transmission scheme, is well recognized for its potential for attaining high rate transmission over frequency selective channels. It can transform such a frequency selective MIMO channel into a set of parallel frequency-flat channels. Implementing space resources based on OFDM i.e., MIMO-OFDM provides higher data rate.
Recently, MIMO systems have been considered in wireless communication systems to increase the capacity. Linear Dispersion Codes are one group of Space-Time Codes with different design methods which are used in MIMO systems. Among them, PSBLLSTCs can provide various data rate and reliable performance in uncorrelated channels. In this book, the influence of unavoidable correlation in MIMO channels on the performance of PSBLLSTCs is studied. It is shown that by applying the optimal phase shifts among transmitted symbols in one layer or between different layers, performance degradation can be reduced. It has also been shown that the optimal phase shifts achieved for uncorrelated systems would not change in presence of correlation. In studying the performance of PSBLLSTCs, high decoding complexity of Maximum Likelihood detection was noticed. In this book, the method of Polar Sphere Decoding is exploited to simplify the decoding process and to provide the possibility of using Sphere Decoding in non-lattice configuration at the receiver side for PSBLLSTCs. It is presented that this decoding process is more than 6 times faster in comparison with ML decoding process.
The aim of this topic is to reduce SER in MIMO System.To investigate a joint diversity scheme and various modulation schemes in a multiple-input multiple-output (MIMO) system. The exact SER of the joint diversity scheme can be derived from M-ary QAM and M-ary PSK modulations in various fading channels. By comparing various fading channels, SER will be reduced and thus performance of SNR in the MIMO systems will be improved.Whenever User increases SER reduced.
Compact antenna structure, natural orthogonality and better line of sight performance are the main reasons why we should consider polarized multi-antenna systems. This book provides a new model for narrow-band correlated Rician dual-polarized MIMO channels. A number of factors including the incorporation of K-factor matrix, asymmetric power imbalance parameters, and space-polarization correlation characteristics make the model in this book useful for most narrow-band applications.
Since the capabilities of MIMO systems was discovered, much research effort has been invested in this field. To exploit their significant capacity and diversity, space-time (ST) codes are the most promising technique for MIMO systems. However, in most applications, the channel state information (CSI) is assumed to be known to the receiver but unknown to the transmitter. To further improve the system performance, the transmitter will be able to adapt the transmission rate based on the level of CSI fed back from the receiver. Our overall goal in this thesis is to develop adaptive space-time schemes over the MIMO wireless channel.
The purpose of the present work is to investigate the advantages of utilizing multi-antenna systems on the capacity of wireless communication systems. This is explicitly due to their capabilities to overcome the impairments of wireless communication systems such as multipath fading and interference. The optimization tasks are carried out via the proliferating global evolutionary techniques to demonstrate their robustness in solving different antenna problems. Different approaches to demonstrate the ability of a linear array of antennas to reduce and/or reject interferences are adopted. First, null placement and sidelobe level reduction are challenged through excitation finding based on the Schelkunoff method and with the aid of genetic algorithms. Next, Particle swarm optimization is used for sidelobe level reduction in nonuniformly spaced linear arrays. Third, it is attempted to incorporate null placement flexibility to the Dolph-Chebychev arrays via position perturbation using Taguchi optimization method. Finally, MIMO system capacity maximization is sought. The purpose is to exploit the dependence of the MIMO channel characteristics on the inter-element spacing between the anten
Nowadays, the requirements in terms of communication are increasing exponentially and getting more diverse. The transmission data rates must be high while maintaining very good quality of service (QoS) despite the very hostile propagation channels. Generally, transmissions that are carried out on mobile radio channels are selective both in time and frequency. To overcome the channel selectivity and allows high transmission data rates, the Long Term Evolution (LTE) standard makes use of the Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) technique. By implementing this technique in the context of mobile transmission, new approaches for time and frequency synchronization, equalization and channel estimation are needed. This book focuses on the study, modeling and development of efficient channel estimation techniques for broadband mobile radio channels and specifically for LTE systems. This book is interesting for both undergraduate and postgraduate students in the field of wireless communication systems. The professional engineers will find also this book useful in improving and designing new wireless communication systems.
In this study report, we have analyzed a hybrid FDMA-TDMA access technique in a cooperative distributive fashion implementing a protocol introduced in (Nabar et al., 2004). A wireless network consists of two users terminal , two relays and two destination terminals. The relays are operating in amplify-and-forward (AF) mode with a xed gain. Two operating modes: cooperation-gain mode and power-gain mode are exploited from source terminals to relays, as it is working in a best channel selection scheme. Vertical BLAST (Bell Laboratories Layered Space Time) or V-BLAST with minimum mean square error (MMSE) nulling has operated at the relays to perfectly detect the joint signals from multiple source terminals. The performance have been analyzed of the end-to-end output signal to noise ratio (SNR) using binary phase shift keying (BPSK) modulation scheme and investigated over Rayleigh and independent and identical (i.i.d.) Nakagami-m fading environments. Subsequently, simulation results show that the proposed scheme can provide better signal quality of uplink users in a cooperation communication systems using hybrid FDMA-TDMA technique.
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.
High spectral efficiency and high transmission data rate are the challenging requirements of wireless broadband communications. The MIMO technology has rapidly gained in popularity due to its powerful performance-enhancing capabilities. Spatial diversity can be obtained by using multiple antennas and space-time codes. For future wireless broadband systems, OFDM is discussed as access scheme. OFDM provides an essentially flat fading channel for each subcarrier by insertion of a cyclic guard interval at each antenna. Therefore, space-time block codes are well suited to be applied in OFDM. We investigate SFBC for OFDM systems with multiple transmit antennas, where coding is applied in the frequency domain rather than in the time domain. In this thesis, performance of two coding techniques STBC and SFBC is analyzed in OFDM. In order to appreciate the performances offered by coding through space and frequency, different simulation scenarios have been proposed where variation of the modulation order , channel fading, antenna selection technique, receiver diversity and effect of power conditions have been considered.
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.
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.
Since delay-sensitive and bandwidth-intense multimedia applications have emerged in the Internet, the demand for network resources has seen a steady increase during the last decade. Specifically, wireless networks have become pervasive and highly populated. These motivations are behind the problems considered in this book. The topic of this book is about the application of game theory, queueing theory and learning techniques in wireless networks under some QoS constraints, especially in partially observable en- vironments. We consider different layers of the protocol stack. In fact, we study the Opportunistic Spectrum Access (OSA) at the Medium Access Control (MAC) layer through Cognitive Radio (CR) approaches. Thereafter, we focus on the congestion con- trol at the transport layer, and we develop some congestion control mechanisms under the TCP protocol.
The focus of this monograph is the comparison of various diversity-combining techniques including some non-conventional hybrid techniques. Diversity-combining is extremely important for design of robust communication systems. It exploits the variability in communication among various channels to minimize errors in overall communication. The monograph also suggests a couple of new techniques derived from the conventional as well as non-conventional ones.
In this work, for a CDMA communication, the per user carrier-to-interference ratio (CINR) enhancement in the Reverse Link (mobile to base station) is analyzed using different antenna array spatial combining algorithms: Optimal Combining (OC) Versus Maximal Ratio Combining (MRC) in a multi-rate (combined voice and data users) multi-antenna scenario. The ratio of the CINR for OC vs. MRC is directly analyzed, i.e. Z=CINROC/CINRMRC. Exact solutions are derived for the statistics of a per user CINROC/CINRMRC improvement, as a function of the high-level interference power to background noise, the gain ratio CINROC/CINRMRC is evaluated in a flat Rayleigh fading communications system with multiple interferers, when the number of interferences L is no less than the number of antenna elements M (L ? M). The gain ratio is derived providing a simple means to determine when OC will exhibit significant gains over MRC. simulations are done to find out the BER performance of optimum combining diversity in correlated Nakagami-m channels and compare with the BER performance of MRC and the influence of interference for MRC and OC are analyzed and discussed
With the rapid growth of multimedia services, future generations of cellular communications require higher data rates and a more reliable transmission link while keeping satisfactory quality of service. In this respect, multiple input multiple-output (MIMO) antenna systems have been considered as an efficient approach to address these demands by offering significant multiplexing and diversity gains over single antenna systems without increasing requirements on radio resources such as bandwidth and power. Although MIMO systems can unfold their huge benefit in cellular base stations, they may face limitations when it comes to their deployment in mobile handsets. This work is based on cooperative communications in wireless networks. We focus on Bit error rate (BER) performance analysis of cooperative communications with either an amplify-and-forward (AF) or decode-and-forward (DF) cooperation protocol using Matlab. We consider the single and multi relay scenario in our simulations.
Multiple Input and Multiple Output (MIMO) systems have shown a tremendous potential to increase the spectral efficiency and the reliability of wireless communication. These aspects are quantified in terms of the spatial multiplexing gain and the diversity gain respectively. There is a trade-off between diversity and multiplexing gains. Bit Interlevead Coded Modulation with Iterative Decoding (BICM-ID) for MIMO channels has been addressed as an effective mean to achieve high data rates while maintaining high diversity. It has been discussed that when signal constellation, interleaver and error control code are fixed, signal mapping has a crucial influence on the error performance of a BICM-ID system. The role of signal mapping applies to the error performance of MIMO-BICM-ID system. In this book, the design of multi-dimensional constellation mapping for MIMO-BICM-ID system is studied. Based on minimizing pair-wise error probability, a design criterion is proposed to find the optimal constellation mapping for MIMO-BICM-ID. Some 2-D and 3-D constellation mappings are presented. Simulation results show significant improvement of Bit Error Rate at high signal to noise ratio.
This book includes the PhD research entitled "Experimental consideration of channel capacity using Multiple Input Multiple Output (MIMO) technology". This work was carried out and completed in the Electronics, Telecommunications and Applied Physics Laboratory, in Physics Department at University of Ioannina, in Greece. Fundamental principles and performance aspects of MIMO systems and wireless channel propagation environment are included in the first chapter of the book. In the following chapters, MIMO platform design and implementation aspects are presented and discussed. The basic methodology that are used in a course of experimental measurements on SIMO and MIMO wireless channel propagation in indoor environment as well as the resulted observations are included in chapter 5. The concluding section of the book presents crucial considerations on MIMO wireless communication systems and proposes some improvements that will simplify the measurements on channel characterization