To broaden the application scenario and reduce energy consumption, we propose an energy-efficient fixed-gain (FG) amplify-and-forward (AF) relay assisted orthog- onal frequency-division multiplexing with index modulation (OFDM-IM) scheme in this thesis. The proposed system needs neither instantaneous channel state informa- tion (CSI) nor performing complicated processing at the relay node. It operates based on a new design of power allocation that minimizes the sum of transmit power at both source and relay node, given an outage probability constraint. Considering the actual situation and combining with the characteristics of normalization research, the pro- posed scheme can be discussed in two scenarios regarding to whether the subcarriers are interfered with by fading and noise independently. Based on the consistency of statistical CSI for each subcarrier, through a series of problem transformation and simplification, this thesis converts the original power allocation problem to a relaxed version and solve the relaxed problem using the convex optimization techniques. To reveal the computing efficiency of the proposed power allocation scheme, we analyze its computational complexity. Numerical simulations substantiate that the proposed optimization scheme has a neglectable loss compared with the brute force search, while the computational complexity could be considerably reduced. As for the sce- nario about the independence of statistical CSI for each subcarrier, an approach of artificial neural network (ANN) based on deep learning is incorporated into the sys- tem, enabling the proposed scheme to achieve a high accuracy comparing perfect optimization scheme. In the processing of power minimization, this study utilizes the adaptive moment estimation (Adam) method to implement back-propagation learn- ing and achieve the power allocation needed.

Recent measurements show that the spectrum is under-utilized by licensed users in wireless communication. Cognitive radio (CR) has been proposed as a suitable solution to manage the inefficient usage of the spectrum and increase coverage area of wireless networks. The concept is based on allowing a group of secondary users (SUs) to share the unused radio spectrum originally owned by the primary user (PUs). The operation of CR should not cause harmful interference to the PUs. In the other hand, relayed transmission increases the coverage and achievable capacity of communication systems and in particular in CR systems. In fact there are many types of cooperative communications, however the two main ones are decode-and-forward (DAF) and amplify-and-forward (AAF). Adaptive relaying scheme is a relaying technique by which the benefits of the amplifying or decode and forward techniques can be achieved by switching the forwarding technique according to the quality of the signal. In this dissertation, we investigate the power allocation for an adaptive relaying protocol (ARP) scheme in cognitive system by maximizing the end-to-end rate and searching the best carriers pairing distribution. The optimization problem is under the interference and power budget constraints. The simulation results confirm the efficiency of the proposed adaptive relaying protocol in comparison to other relaying techniques, and the consequence of the choice of the pairing strategy.

In this dissertation a computationally efficient cognitive multiple-input multiple-output (MIMO) orthogonal frequency division duplexing (OFDM) detector is designed to decode perfect space-time coded signals which are able maximize the diversity and multiplexing properties of a rich fading MIMO channel. The adaptive nature of the cognitive detector allows a MIMO OFDM communication system to better meet to needs of future wireless communication networks which require both high reliability and low run-time complexity depending on the propagation environment. The cognitive detector in conjunction with perfect space-time coding is able to achieve up to a 2 dB bit-error rate (BER) improvement at low signal-to-noise ratio (SNR) while also achieving comparable runtime complexity in high SNR scenarios.

The contents of this thesis is a delineation of the European Standard ETSI EN 300 744 for terrestrial digital video broadcasting (DVB-T) and a description of created OFDM coder and decoder for baseband signal transmission in 2K mode without error correction capabilities. The proper function of both devices is verified by means of Matlab simulations and practically implemented into Texas Instruments’ digital signal processor TMS320C6711 using Starter Kits.

Main goal of this dissertation is read over principal and properties of the OFDM modulation. Onward we become acquainted with basic methods for PAPR dynamics reduction in OFDM such as Clipping or Interleaving. Simulation of reduction methods will be realized in Scilab environment, in which are made basic functions for OFDM modulator and demodulator. Furthermore there are created functions for PAPR reduction methods. All established functions are implemented in the GUI.

This dissertation examines data transfers along the existing lines of cable TV. PLC equipment has been selected as the focus of this examination. The essay examines the question of Multicarrier modulation and focuses more specifically onto the problem of OFDM modulation, which is being used by the selected equipment. It further describes the process of integration of PLC equipment into the cable TV network, modifications of the CATV and the basic topology of the created data networks. The essay also offers a closer look onto a PLC modem and Head End from Corinex that have been used in the implementation of a data network in a selected rural settlement. The author has also raised the issue of the problems connected with cable wires connected with this particular type of data transfers and the solutions of some of the encountered problems. The characteristics of this network have then been measured during normal operation of the created network. Measurements have been carried out in order to determine the transfer speed on a physical and transfer level, the SNR of specific connections and the signal attenuation. The measurements have confirmed the suitability of the used PLC equipment for the purposes of data transfer along the cable TV lines as far as data speed and signal strength was concerned. A map of the particular cable TV lines and the PLC equipment has been included in the attachment.

The thesis deals with analysis of the PLC (Power Line Communication) system for data communications through powerlines. In the introduction describes the technology of data transmission through the energy network and is divided into categories corresponding with the explanation of the various specifications and features. Different types of coding, affecting the transmitted signal interference and modulation techniques used in a PLC are also described. The practical part is made up of telecommunications network model with transmission channel realized as additive white noise. The model can setup different types of modulation and coding in relate with the signal to noise ratio and bit error rates. The individual blocks settings are described in detail. The model was simulated. The results of simulation are displayed and evaluated at the end of work.

The theme of this thesis is simulation of DVB-C2 transmission. The first part of this thesis is focused mainly on theory, where it describes differences between digital and analog television transmission. The project also explains principle of operation DVB-C and DVB-C2 systems with focus on channel coding a modulation. Application for simulation of DVB-C2 transmission, which is developed in the MATLAB environment is described in the second part. The last part of this thesis includes results of simulations of DVB-C2 transmission and their comparison with measured values of DVB-C transmission.

Orthogonal frequency division multiplexing (OFDM) has become a very popular method for high-data-rate communication. However, it is well known that OFDM is plagued by a large peak-to-average power ratio (PAPR) problem. This high PAPR results in overdesigned power amplifiers, which amongst other things leads to inefficient amplifier usage, which is undesirable. Various methods have been recommended to reduce the PAPR of an OFDM transmission; however, all these methods result in a number of drawbacks. In this thesis, a novel method called offset modulation (OM-OFDM) is proposed to control the PAPR of an OFDM signal. The proposed OM-OFDM method does not result in a number of the drawbacks being experienced by current methods in the field. The theoretical bandwidth occupancy and theoretical bit error rate (BER) expression for an OM-OFDM transmission is derived. A newly applied power performance decision metric is also introduced, which can be utilised throughout the PAPR field, in order to compare various methods. The proposed OM-OFDM method appears to be similar to a well-known constant envelope OFDM (CE-OFDM) transmission. The modulation, structural and performance differences between an OM-OFDM and a CE-OFDM method are discussed. By applying the power performance decision metric, the OM-OFDM method is shown to offer significant performance gains when compared to CE-OFDM and traditional OFDM transmissions. In addition, the OM-OFDM method is able to accurately control the PAPR of a transmission for a targeted BER. By applying the power performance decision metric and complementary cumulative distribution function (CCDF), the proposed OM-OFDM method is shown to offer further performance gains when compared to existing PAPR methods, under frequency selective fading conditions. In this thesis, the OM-OFDM method has been combined with an existing active constellation extended (ACE) PAPR reduction method. To introduce a novel method called offset modulation with active constellation extension (OM-ACE), to control the PAPR of an OFDM signal. The theoretical BER expression for an OM-ACE transmission is presented and validated. Thereafter, by applying the decision metric and CCDF, the OM-ACE method is shown to offer performance improvements when compared to various PAPR methods. The use of OM-OFDM for cognitive radio applications is also investigated. Cognitive radio applications require transmissions that are easily detectable. The detection characteristics of an OM-OFDM and OFDM transmission are studied by using receiver operating characteristic curves. A derivation of a simplified theoretical closed-form expression, which relates the probability of a missed detection to the probability of a false alarm, for an unknown deterministic signal, at various signal-to-noise ratio (SNR) values is derived and validated. Previous expressions have been derived, which relate the probability of a missed detection to the probability of a false alarm. However, they have not been presented in such a generic closed-form expression that can be used for any unknown deterministic signal (for instance OFDM and OM-OFDM). Thereafter, an examination of the spectrum characteristics of an OM-OFDM transmission indicates its attractive detection characteristics. The proposed OM-OFDM method is further shown to operate at a significantly lower SNR value than an OFDM transmission, while still offering better detection characteristics than that of an OFDM transmission under Rician, Rayleigh and frequency selective fading channel conditions. In addition to its attractive PAPR properties, OM-OFDM also offers good detection characteristics for cognitive radio applications. These aspects make OM-OFDM a promising candidate for future deployment. / Thesis (PhD)--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted

UWB is a promising technology for short-range high-rate wireless applicationa.It is able to providemaximal 480Mbps data-rate at a distance of 2 meters in realisticindoormulti-path environments. UWB technology is widely applied to the next generation WPAN as well as the wireless accessof consumer electronics at home. Recently, Multi-Band OFDM based UWB technology proposed by WiMedia has been selected as the international standard by ISO. In China, a new transmission architecture based on Dual-Carrier OFDM technology is adopted as UWB standard draft. Comparing to MB-OFDM based UWB system, DC-OFDM based UWB system has multiple advantages, like more spectrum resource,lower requirements on devices, etc. Besides, it is compatiblewith existing MB-OFDM based UWB technology. Therefore, DC-OFDM based UWB is more flexible. Synchronizationis the first step atthe receiver digital baseband, which is of tremendous importance in any wireless communication systems. The performance of synchronization directly determines whether the receiver can pick up radio signals correctly or not, whether the baseband modules can fulfill the digital signal processing effectively or not. The synchronization process in OFDM system can be briefly divided into two parts: symbol timing and frequency synchronization. Symbol timing serves to judge the starting position of OFDM symbolsafter considering the impact of multi-path fading channel.While the frequency synchronization estimates the multiple imperfections in analog front-end signal processing and make proper compensation. This thesis puts the emphasis on synchronization issues in DC-OFDM based UWB systems. We are the first to analyze the synchronization algorithm as well as the hardware implementation method tailored for DC-OFDM based UWB system. We also present the VLSI implementation result for synchronization module. The thesis consists of symbol timing and frequency synchronization. Regarding on the symbol timing, we analyze the impact of several synchronization errors inOFDM system. After that, we divide the synchronization process into four modulesby functionality: packet detection, coarse timing, TFC detection and fine timing. The internal parameters in each moduleare determined by system simulations. In the aspect of algorithm development, we adopt the joint auto-correlation and cross-correlation method to meet the requirements of UWB system in different indoor multi-path environments, and therefore achieve the robustness. In the aspect of hardware implementation, we put the attention on the structure of some key modules in symbol timing and their VLSI implementation result, such as auto-correlator, cross-correlator, real-number divider, etc. Regarding on the frequency synchronization, we first investigate the multiple analog front-end imperfections in OFDM system, like CFO, SFO and I/Q imbalance, and present their mathematics models respectively in DC-OFDM based UWB system.After that, we analyze the performance degradation in OFDM system due to these non-ideal effects by the metric of EVM. RF designer can build the connection between mismatching parameters and performance degradation by referring to the analysis. Hence, theRF designer is able to traceout the outline of system design. In the aspect of algorithm development, we explore the intrinsic character of I/Q imbalancewhich causes the image interference. Then, we design a set of new training sequences based on phase rotation and give the corresponding estimation algorithm.The simulation result shows that the new training sequence is able to obtain the diversity message introduced by I/Q imbalance and therefore achieve the diversity gain during demodulation process. In order to deal with the challenging situation where multiple analog front-end imperfections co-exist, we propose a joint estimation and compensation scheme. In the aspect of hardware implementation, we present the hardware structure of CFO estimation and compensation module catered for DC-OFDM based UWB system, with the emphasis on CORDIC unit that is responsible for triangle calculations. The VLSI implementation result shows that the proposed CFO estimation and compensation module satisfies the timing and resource requirements in DC-OFDM based UWB system. In the last, we present the prospective research area in 60-GHz applications. It includes multiplenon-ideal impairments, like phase noise, non-linear power amplification, DC offset, ADCs mismatch, etc. It is even more challenging to develop joint estimation and compensation scheme for these non-ideal effects.