abstract: Practical communication systems are subject to errors due to imperfect time alignment among the communicating nodes. Timing errors can occur in different forms depending on the underlying communication scenario. This doctoral study considers two different classes of asynchronous systems; point-to-point (P2P) communication systems with synchronization errors, and asynchronous cooperative systems. In particular, the focus is on an information theoretic analysis for P2P systems with synchronization errors and developing new signaling solutions for several asynchronous cooperative communication systems. The first part of the dissertation presents several bounds on the capacity of the P2P systems with synchronization errors. First, binary insertion and deletion channels are considered where lower bounds on the mutual information between the input and output sequences are computed for independent uniformly distributed (i.u.d.) inputs. Then, a channel suffering from both synchronization errors and additive noise is considered as a serial concatenation of a synchronization error-only channel and an additive noise channel. It is proved that the capacity of the original channel is lower bounded in terms of the synchronization error-only channel capacity and the parameters of both channels. On a different front, to better characterize the deletion channel capacity, the capacity of three independent deletion channels with different deletion probabilities are related through an inequality resulting in the tightest upper bound on the deletion channel capacity for deletion probabilities larger than 0.65. Furthermore, the first non-trivial upper bound on the 2K-ary input deletion channel capacity is provided by relating the 2K-ary input deletion channel capacity with the binary deletion channel capacity through an inequality. The second part of the dissertation develops two new relaying schemes to alleviate asynchronism issues in cooperative communications. The first one is a single carrier (SC)-based scheme providing a spectrally efficient Alamouti code structure at the receiver under flat fading channel conditions by reducing the overhead needed to overcome the asynchronism and obtain spatial diversity. The second one is an orthogonal frequency division multiplexing (OFDM)-based approach useful for asynchronous cooperative systems experiencing excessive relative delays among the relays under frequency-selective channel conditions to achieve a delay diversity structure at the receiver and extract spatial diversity. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

Abstract The present dissertation deals with the evaluation of multiple-input multiple-output (MIMO) radio channel characteristics from time-division multiplexing (TDM)-switched MIMO channel sounding. The research can be divided into three main areas. First, the impacts of phase noise in TDM-switched MIMO channel sounding on channel capacity are studied. Second, we focus on those impacts on channel parameter estimation using the SAGE algorithm. And in the last part, spatial correlation, channel eigenvalue distribution, and ergodic capacity in realistic environments are analyzed. The rationale behind the first two areas is that most advanced MIMO radio channel sounders employ the TDM technique, which has significant problems from phase noise of the TX and RX phase locked loop (PLL) oscillators causing measurement errors in terms of estimated channel capacity and parameters. We propose statistical models that reproduce the capacity estimates. The effects of the sounding mode (SM), the length of pseudo-random noise (PN) sequence L of the sounding signal, and the system size are disclosed. The distinctive basis is to consider the impact of the actual phase noise in TDM switched MIMO channel sounding, instead of assuming white Gaussian-type phase noise. In a reality, the short-term phase noise component affecting one measurement cycle of a MIMO system plays an important role in the traditional estimators of the radio channel parameters and capacity. We show that the performance impairment is less than that been under the hypothesis of uncorrelated white Gaussian phase-noises samples. The difference is due to the non-vanishing correlation of phase-noise within the measurement cycle. Two approaches to mitigating the impact of phase noise are proposed. The former is the simple and efficient sliding averaging method, where the signal-to-noise ratio (SNR) of the channel impulse response can be increased. The latter is the choice of SM and L, which is more thorough. In the second part, two approaches to mitigating its impact on channel parameter estimation using the SAGE algorithm are also discussed. Besides the sliding averaging, which in general can increase the SNR, the new SAGE algorithm based channel parameter estimation based on the improved signal model accounting for the phase noise in the measurement device is proposed. Finally, the channel eigenvalue distribution and ergodic capacity based on complex hypergeometric functions and their asymptotic characteristics are analyzed. It is shown that the derived theoretical expressions closely approximate the simulated results of the measured finite-dimensional MIMO channels. The spatial correlation and the eigenvalue statistics in frequency selective channels for single and dual polarized antennas are investigated. This knowledge is useful when different MIMO and beamforming techniques are applied.

This thesis deals with analysis and modelling of power line communications. The main aim is to examine the effects influencing transsmision of communication signals on powerline networks and theoretical capacity of the PLC channel using PLC framework created in NS-3. The introduction summarizes the theoretical knowledge in the area of data transmission over power line distribution network. Different types of noise and possibilities of calculation of theoretical transmission capacity are described as well. Several simple simulations are realized in practical part of this paper. These simulations explore the influence of the distance between the transmitter and receiver, length, impedance and number of branches between these nodes, affect of the type of modulation and noise on the transfer function as well as the capacity of the channel. There are also some simulations for large topology based on real position of electrometer. The main focus is to find positions of repeaters to ensure that some nodes of the topology can communicate.

The diploma thesis deals with analysis and modeling of power line communication using NS-3. The introduction part summarizes basic information about PLC technology, distribution grids, and broadband standards. This is followed by the analysis of the transmission line and modulation method. Furthermore, the simulation tool and possibilities of its extension are described. The influence of different cross-section and type of line on channel capacity is examined in the practical part of this paper. The influence of repeaters on bitrate is examined as well. The medium-voltage line was implemented and further scenarios dealing with bitrate or optimal level of noise. The focus of the last part is to find the repeaters on the path and to determine the capacity and bitrate on the path of the large topology.

In calling for the deployment of high-capacity telecommunications infrastructures, the Clinton Administration is relying on market forces to drive demand toward self-sustaining development. There is little doubt that many firms will embrace the new telecommunications services for a variety of reasons including market differentiation, vertical market integration, and other organization-specific factors. However, there is little evidence at the firm level that adopting the use of increased-capacity telecommunications technologies is associated with improvements in firm profitability. This study seeks to identify the presence of impacts on firm income that can be associated with the adoption of T1 telecommunications services.

In recent years, multiple-input multiple-output (MIMO)systems appear to be very promising since they can provide highdata rates in environments with sucient scattering byexploiting the spatial domain. To design a real MIMO wirelesssystem and predict its performance under certain circumstances,it is necessary to have accurate MIMO wireless channel modelsfor dierent scenarios. This thesis presents dierent models forindoor MIMO radio propagation channels based on 5.2 GHz indoorMIMO channel measurements.The recent research on MIMO radio channel modeling isbriey reviewed in this thesis. The models are categorized intonon-physical and physical models. The non-physical modelsprimarily rely on the statistical characteristics of MIMOchannels obtained from the measured data while the physicalmodels describe the MIMO channel (or its distribution) via somephysical parameters. The relationships between dierent modelsare also discussed.For the narrowband case, a non line-of-sight (NLOS)indoor MIMO channel model is presented. The model is based on aKronecker structure of the channel covariance matrix and thefact that the channel is complex Gaussian. It is extended tothe line-of-sight (LOS) scenario by estimating and modeling thedominant component separately.As for the wideband case, two NLOS MIMO channel modelsare proposed. The rst model uses the power delay prole and theKronecker structure of the second order moments of each channeltap to model the wideband MIMO channel while the second modelcombines a simple single-input single-output (SISO) model withthe same Kronecker structure of the second order moments.Monte-Carlo simulations are used to generate indoor MIMOchannel realizations according to the above models. The resultsare compared with the measured data and good agreement has beenobserved. / <p>NR 20140805</p>

This thesis explores and develops a simulation model for Line of Sight(LoS) Multiple-Input Multiple-Output (MIMO) systems in complex environments. The focus will be on implementing a 2 × 2-MIMO system in order to study phase differences of the received signals. The propagation of the electromagnetic waves is based on an existing wave propagation model that uses the parabolic equation approach. This work aims to deepen our understanding of a 2 × 2-MIMO systems’ behavior under various conditions, including free space propagation but also standard atmospheric and ducting environments. The results demonstrate that the parabolic equation method aligns well with theoretical expectations, validating its use for modeling MIMO systems.The findings have significant implications for optimizing the design and operation of wireless communication systems. The thesis also outlines potential future work, including empirical model verification, development of alternative models, and extension to more complex MIMO systems.

Multiple-input-multiple-output (MIMO) wireless systems use multiple antenna elements at the transmitter and receiver to offer improved spectral efficiency over traditional single antenna systems. In these systems, properties of the transmit and receive antenna arrays play a key role in determining the overall performance of the system. This thesis derives an upper bound on ergodic (average) channel capacity which formally links good antenna diversity performance with good ergodic capacity. As a result of this derivation, antenna arrays with good ergodic capacity performance are designed in this thesis by designing antenna arrays with near-optimal diversity gain. Several approaches are developed to design antenna array elements which achieve near-optimal diversity. These design methods only require an array geometry and the power azimuth spectrum of the propagation environment. Examples and analysis are included that illustrate advantages and disadvantages of each design technique. Three different array geometries are also investigated. Diversity performance results for each design technique and array geometry, averaged over an ensemble of typical power azimuth spectrums, are presented and compared. This analysis shows that the diversity gain achieved by the best design approach is, on average, less than 1.5 dB below the optimal diversity gain.

This thesis discuss on new technique called space time block coding (especially Alamouti's code) which is used to increase capacity and reliability of data transmission over time varying multi-path fading channel. The over all work of the thesis included in the following four chapters. In chapter-1 we are going to cover some theoretical part which is useful to understand thesis work and in chapter-2 we will discuss the comparison between simple space time block code (Alamouti's code) and MRRC (Maximum Ratio Receiver Combining) which is receiver diversity and then in chapter-3 we will see the channel capacity &amp; probability error performance for 2x2 Alamouti code over Rayleigh and Rice fading channel .Finally the conclusion and further work included in chapter-4.

The transmission rate and reliability are the most crucial elements of a communication system on sea platforms. In this thesis, the performance of a high speed and reliable communication system that can be used on ship to ship sea platforms will be evaluated. The two ray channel model is used in order to characterize the channel considering the refraction and reflection. Using the channel model, the path loss and the Shannon channel capacities are obtained for different systems. In order to increase the system performance, frequency diversity technique is used and a detailed comparison of diversity combining techniques is provided. As an alternative to Shannon channel capacity, cut off rate analysis is considered to get more realistic results about the rate of the communication system in that it takes modulation into account and the results are compared with the channel capacity. Block fading model and jamming effects on the achievable rate of the system is considered for different linear modulation techniques. Finally, an OFDM system design is given as an example using the tools obtained in this work.