Download or read book influence of channel estimation errors in mimo ofdm systems written by Xavier Llorens Sole and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Signal Processing Channel Estimation and Link Adaptation in MIMO OFDM Systems written by Jianjun Ran and published by Cuvillier Verlag. This book was released on 2008 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Antenna Selection for MIMO OFDM Systems with Channel Estimation Error written by Adarsh Bangalore Narasimhamurthy and published by . This book was released on 2007 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Channel Estimation and Data Detection for Mobile MIMO OFDM Systems written by Jie Gao and published by . This book was released on 2005 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: Designing spectral efficient, high-speed wireless links that offer high quality- of-service and range capability has been a critical research and engineering challenge. In this thesis, we mainly address the complexity and performance issues of channel estimation and data detection in multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems over time-varying channels. We derive the probability density function (pdf) expressions of the condition number (i.e., the maximum-to-minimum-singular-value ratio, MMSVR) of the channel state information matrix of MIMO OFDM systems. It is shown that this ratio is directly related to the noise enhancement in open-loop systems and provides a significant insight on the system capacity. A decision-directed (DD) maximum a posteriori probability (MAP) channel estimation scheme of MIMO systems is derived. Error performance of a zero- forcing receiver with the DD MAP and perfect channel estimates is provided and compared. This scheme has a low complexity and can be applied to time-varying Rayleigh fading channels with an arbitrary spaced-time correlation function. We propose an iterative channel estimation and data detection scheme for MIMO OFDM systems in the presence of inter-carrier-interference (ICI) due to the nature of time-varying channels. An ICI-based minimum-mean-square error (MMSE) detection scheme is derived. An expectation-maximization (EM) based least square (LS) channel estimator is proposed to minimize the mean-square error (MSE) of the channel estimates and to reduce the complexity of the implementation. With the estimate of the channel and initially detected symbols, ICI is estimated and removed from the received signal. Thus more accurate estimation of the channel and data detection can be obtained in the next iteration. An EM-based MAP channel estimator is derived by exploiting the frequency/time correlation of the pilot and data sub-carriers. Performance comparison is made between the proposed schemes and the ideal case - time-invariant channels and perfect channel estimation. We optimize the data transmission by exploiting the long term correlation characteristics. The transmitted data is successively detected without an error floor in spatially correlated channels. The algorithms proposed in this thesis allow low-complexity implementation of channel estimation and data detection for MIMO OFDM systems over time-varying fading channels, while providing good error performance.

Download or read book EFFECTIVE SPARSE CHANNEL ESTIMATION TECHNIQUE FOR MIMO OFDM SYSTEM written by Dr.Maddala Vijayalakshmi and published by Archers & Elevators Publishing House. This book was released on with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Joint Iterative Channel and Data Estimation in High Mobility MIMO OFDM Systems written by Stephan Sand and published by Logos Verlag Berlin GmbH. This book was released on 2010 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Channel Estimation Errors on Receiver Selection Combining Diversity for Alamouti MIMO Systems written by Wenyu Li and published by . This book was released on 2005 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book PERFORMANCE ANALYSIS OF MIMO OFDM SYSTEM USING CODING AND EQUALIZATION written by G.KRISHNA REDDY and published by Archers & Elevators Publishing House. This book was released on with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Studies on the Performance and Impact of Channel Estimation in MIMO and OFDM Systems written by Michael David Larsen and published by . This book was released on 2010 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second part of this dissertation uses the CRB once again, this time as a tool for evaluating the potential performance of MIMO-OFDM channel estimation and prediction. Bounds are found for several parametric time-varying wideband MIMO-OFDM channel models, and numerical evaluations of these bounds are used to illuminate several interesting features regarding the estimation and prediction of MIMO-OFDM channels.

Download or read book STUDY OF CHANNEL ESTIMATION FO written by Wen Zhou and published by Open Dissertation Press. This book was released on 2017-01-26 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "A Study of Channel Estimation for OFDM Systems and System Capacity for MIMO-OFDM Systems" by Wen, Zhou, 周雯, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. DOI: 10.5353/th_b4555585 Subjects: Orthogonal frequency division multiplexing - Mathematical models MIMO systems - Mathematical models

Download or read book Channel Estimation and Non linear Transceiver Designs for MIMO OFDM Relay Systems written by Andrew Paul Millar and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiple-input multiple output (MIMO) systems deploy multiple antennas at either end of a communication link and can provide significant benefits compared to traditional single antenna systems, such as increased data rates through spatial multiplexing gain, and/or improved link reliability through diversity techniques. Recently, the natural extension of utilising multiple antennas in relay networks, known as MIMO relaying, has attracted significant research attention due to the fact that the benefits of MIMO can be coupled with extended network coverage through the use of relaying devices. This thesis concentrates on the design and analysis of different aspects of MIMO relay systems communicating over frequency selective channels with the use of orthogonal frequency division multiplexing (OFDM). The first focus of this thesis is on the development of training based channel estimation algorithms for two-hop MIMO OFDM relaying. In the first phase of channel estimation the relay-destination channel is estimated using conventional point-to-point MIMO estimation techniques. In the second phase, the source sends known training symbols to the relay, which precodes the received symbols and forwards them to the destination. In order to estimate the source-relay channel at the destination, an iterative algorithm is derived, which involves sequentially solving a number of convex optimisation problems and has guaranteed convergence. Since the proposed iterative algorithm may be too computationally complex for practical systems, a simplified approach is also derived where the channel estimation processors can be calculated in closed form. Under the assumption of perfect channel state information (CSI), we then develop non-linear transceiver designs for MIMO OFDM relay systems, focusing specifically on decision feedback equalisation (DFE) and Tomlinson Harashima precoding (THP). The optimal source and relay precoding matrices are derived that minimise the arithmetic mean square error (MSE) subject to source and relay transmission power constraints, when either a zero forcing (ZF) or minimum mean square error (MMSE) equaliser is used at the destination. Simulation results demonstrate that the proposed non-linear solutions outperform linear transceivers in terms of bit error rate (BER) and MSE. For the case of imperfect CSI at all nodes, robust DFE and THP transceivers are then considered that aim to minimise the expected artithmetic MSE subject to the source and relay transmission power constraints. The channel estimation errors are modelled as being drawn from matrix variate Gaussian distributions with known mean and covariance. The source and relay precoder structures are derived for the case that the optimal MMSE equaliser is used at the destination. The derived precoder structures are shown to be optimal for the special case that the channel estimation errors are uncorrelated. Simulation results demonstrate the robustness of the proposed algorithms to channel estimation errors.

Download or read book Joint Estimation of CFO and CIR in MIMO OFDM Systems written by Thavalapill Smith and published by LAP Lambert Academic Publishing. This book was released on 2015-06-24 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently the integration of the Multiple-Input Multiple-Output (MIMO) architectures and Orthogonal Frequency Division Multiplexing (OFDM) technique has been widely considered as a potential strategy to enhance data rate, capacity and quality of broadband wireless OFDM systems.However, the inherent drawback of OFDM-based systems is their susceptibility to synchronization errors such as the Carrier Frequency Offset (CFO) and the primary challenge in MIMO based systems is the increasing complexity in channel estimation as the number of antennas increases.Various joint CFO and channel estimation for OFDM as well as MIMO-OFDM systems have been proposed till date. In this report, we consider an iterative Expectation-Maximization (EM) algorithm for the joint estimation of CFO and Channel Impulse Response(CIR) for MIMO-OFDM system in frequency selective fading channel.Simulation results show that EM algorithm gives marginally better performance over pilot-assisted Maximum Likelihood (ML)- based algorithm, proposed recently, in terms of MSE of both channel and frequency offset estimator

Download or read book OFDM for Optical and Radio Communications written by Xia Li and published by . This book was released on 2009 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents two original ontributions on orthogonal frequency division multiplexing (OFDM). The first is a thorough investigation of the error performance and channel capacity of asymmetrically clipped optical OFDM (ACO-OFDM). ACO-OFDM is a modulation scheme designed specifically for optical communications. The second concerns the use of multiple-input multiple-output (MIMO) OFDM in radio frequency (RF) systems. A new scheme which uses polynomial cancellation coding (PCC) OFDM with time offsets is proposed. This new scheme is robust to both carrier frequency offset (CFO) and channel estimation errors. OFDM has been used extensively to reduce the effect of dispersion in wired and wireless RF systems. Although dispersion is also a problem in optical wireless systems, OFDM has not until recently been considered for use in these. This is because optical wireless systems use intensity modulation (IM) and so the transmitted signals must be nonnegative and as a result conventional OFDM signals which are bipolar cannot be used directly. ACO-OFDM and DC biased optical OFDM (DCO-OFDM) are two non-negative forms of OFDM developed for optical systems. Both are robust to ISI but ACO-OFDM is in most cases much more power efficient. In this thesis results are presented for the performance of ACO-OFDM, DCO-OFDM and conventional optical modulation schemes such as on-off keying (OOK) and pulse position modulation (PPM) for both dispersive and non-dispersive channels. These show that ACO-OFDM is more tolerant to dispersion and requires less optical power than the other modulation schemes. To investigate the theoretical limits of an ACO-OFDM system, closed form analytical expressions for the channel capacity of ACO-OFDM are derived both for a flat channel and for representative dispersive optical wireless channels. The capacity of ACO-OFDM cannot be compared with the general case of an intensity modulated signal, because no general solution for this has yet been found. Instead the mutual information of an ACO-OFDM signal is calculated and compared with two other signal distributions: an exponential distribution and a clipped-Gaussian distribution.The combination of OFDM and MIMO has been used in several radio standards. However, MIMO OFDM systems like single-input single-output (SISO) OFDM systems are very sensitive to CFO. An improved MIMO PCC OFDM system is proposed in this thesis. In this system, the signals transmitted from different antennae have different time offsets. At the receiver, OFDM symbols are demodulated by using each of these time offsets in a matched detection window. This system shows better performance than a MIMO PCC OFDM system without time offsets in two cases: when there are channel estimation errors and in MIMO systems with more transmit antennae than receive antennae.

Download or read book A New MAP Based Channel Estimation Technique for Multiple input Multiple output MIMO Systems written by Wajih Hoteit and published by . This book was released on 2006 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Proceeding of Fifth International Conference on Microelectronics Computing and Communication Systems written by Vijay Nath and published by Springer Nature. This book was released on 2021-09-09 with total page 855 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents high-quality papers from the Fifth International Conference on Microelectronics, Computing & Communication Systems (MCCS 2020). It discusses the latest technological trends and advances in MEMS and nanoelectronics, wireless communication, optical communication, instrumentation, signal processing, image processing, bioengineering, green energy, hybrid vehicles, environmental science, weather forecasting, cloud computing, renewable energy, RFID, CMOS sensors, actuators, transducers, telemetry systems, embedded systems and sensor network applications. It includes papers based on original theoretical, practical and experimental simulations, development, applications, measurements and testing. The applications and solutions discussed here provide excellent reference material for future product development.

Download or read book The Effects of Channel Estimation Errors on Wideband CDMA Systems with Path Frequency Time and Space Diversity written by Lucy Lok-Kwan Chong and published by . This book was released on 2001 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Signal perturbation free Semi blind Channel Estimation for MIMO OFDM Systems written by Feng Wan and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) has been considered as a strong candidate for the beyond 3G (B3G) wireless communication systems, due to its high data-rate wireless transmission performance. It is well known that the advantages promised by MIMO-OFDM systems rely on the precise knowledge of the channel state information (CSI). In real wireless environments, however, the channel condition is unknown. Therefore, channel estimation is of crucial importance in MIMO-OFDM systems. Semi-blind channel estimation as a combination of the training-based or pilot-assisted method and the pure blind approach is considered to be a feasible solution for practical wireless systems due to its better estimation accuracy as well as spectral efficiency. In this thesis, we address the semi-blind channel estimation issue of MIMO-OFDM systems with an objective to develop very efficient channel estimation approaches. In the first part of the dissertation, several nulling-based semi-blind approaches are presented for the estimation of time-domain MIMO-OFDM channels. By incorporating a blind constraint that is derived from MIMO linear prediction (LP) into a training-based least-square method, a semi-blind solution for the time-domain channel estimation is first obtained. It is revealed through a perturbation analysis that the semi-blind solution is not subject to signal perturbation and therefore is superior to pure blind estimation methods. The LP-based semi-blind method is then extended for the channel estimation of MIMO-OFDM systems with pulse-shaping. By exploiting the pulse-shaping filter in the transmitter and the matched filter in the receiver, a very efficient semi-blind approach is developed for the estimation of sampling duration based multipath channels. A frequency-domain correlation matrix estimation algorithm is also presented to facilitate the computation of time-domain second-order statistics required in the LP-based method. The nulling-based semi-blind estimation issue of sparse MIMO-OFDM channels is also addressed. By disclosing and using a relationship between the positions of the most significant taps (MST) of the sparse channel and the lags of nonzero correlation matrices of the received signal, a novel estimation approach consisting of the MST detection and the sparse channel estimation, both in a semi-blind fashion, is developed. An intensive simulation study of all the proposed nulling-based methods with comparison to some existing techniques is conducted, showing a significant superiority of the new methodologies. The second part of the dissertation is dedicated to the development of two signal-perturbation-free (SPF) semi-blind channel estimation algorithms based on a novel transmit scheme that bears partial information of the second-order statistics of the transmitted signal to receiver. It is proved that the new transmit scheme can completely cancel the signal perturbation error in the noise-free case, thereby improving largely the estimation accuracy of correlation matrix for channel estimation in noisy conditions. It is also shown that the overhead caused by the transmission of the 8PF data is negligible as compared to that of regular pilot signals. By using the proposed transmit scheme, a whitening rotation (WR)-based algorithm is first developed for frequency-domain MIMO-OFDM channel estimation. It is shown through both theoretical analysis and simulation study that the new WR-based algorithm significantly outperforms the conventional WR-based method and the nulling-based semi-blind method. By using MIMO linear prediction, the new WR-based algorithm utilizing the 8PF transmit scheme is then extended for time-domain MIMO-OFDM channel estimation. Computer simulations show that the proposed signal-perturbation-free LP-based semi-blind solution performs much better than the LP semi-blind method without using the proposed transmit scheme, the LS method as well as the nulling-based semi-blind method in terms of the MSE of the channel estimate.