Initial synchronisation of wideband and UWB direct sequence systems: single- and multiple-antenna aided solutions

This survey guides the reader through the open literature on the principle of initial synchronisation in single-antenna-assisted single- and multi-carrier Code Division Multiple Access (CDMA) as well as Direct Sequence-Ultra WideBand (DS-UWB) systems, with special emphasis on the DownLink (DL). There is a paucity of up-to-date surveys and review articles on initial synchronization solutions for MIMO-aided and cooperative systems - even though there is a plethora of papers on both MIMOs and on cooperative systems, which assume perfect synchronization. Hence this paper aims to ?ll the related gap in the literature

Wavelet-based multi-carrier code division multiple access systems

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years

Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions

WIMAX 802.16 PHYSICAL LAYER IMPLEMENTATION AND WIMAX COVERAGE AND PLANNING.

Over the last decade, the impact of wireless communication on the way we live and carry out business has been surpassed only by impact of the internet. But wireless communications is still in its infancy and the next stage of its development will be supplementing or replacing network infrastructure that was traditionally wired. The advent and adoption of the computer and the myriad software packages available for it offered the ability to generate a new wave of communication combining art, pictures, music and words into a targeted multimedia presentation. These presentations are large so that is requires higher bandwidth transmission facilities. Coupling this with the need for mobility, the solution would be wireless data delivery putting in consideration the bandwidth request. WiMAX technology is based on the IEEE 802.16 standard, it was only recently when the first IEEE 802.16 based equipment broadband began to enter the market. The additional spectrum, bandwidth and throughout capabilities of 802.16 will remarkably improve wireless data delivery and should allows even more wireless data service areas to be deployed economically. In this Final Year Project, a study about the IEEE 802.16 standard and mainly concentrate on the 802.16 PHY Layer behaviors was performed. A Simulink based model for the 802.16 PHY Layer was built for simulation and performance evaluation of WiMAX. MATLA

A theoretical framework for soft-information-based synchronization in iterative (Turbo) receivers

This contribution considers turbo synchronization, that is to say, the use of soft data information to estimate parameters like carrier phase, frequency, or timing offsets of a modulated signal within an iterative data demodulator. In turbo synchronization, the receiver exploits the soft decisions computed at each turbo decoding iteration to provide a reliable estimate of some signal parameters. The aim of our paper is to show that such “turbo-estimation” approach can be regarded as a special case of the expectation-maximization (EM) algorithm. This leads to a general theoretical framework for turbo synchronization that allows to derive parameter estimation procedures for carrier phase and frequency offset, as well as for timing offset and signal amplitude. The proposed mathematical framework is illustrated by simulation results reported for the particular case of carrier phase and frequency offsets estimation of a turbo-coded 16-QAM signal

MIMO signal processing in offset-QAM based filter bank multicarrier systems

Next-generation communication systems have to comply with very strict requirements for increased flexibility in heterogeneous environments, high spectral efficiency, and agility of carrier aggregation. This fact motivates research in advanced multicarrier modulation (MCM) schemes, such as filter bank-based multicarrier (FBMC) modulation. This paper focuses on the offset quadrature amplitude modulation (OQAM)-based FBMC variant, known as FBMC/OQAM, which presents outstanding spectral efficiency and confinement in a number of channels and applications. Its special nature, however, generates a number of new signal processing challenges that are not present in other MCM schemes, notably, in orthogonal-frequency-division multiplexing (OFDM). In multiple-input multiple-output (MIMO) architectures, which are expected to play a primary role in future communication systems, these challenges are intensified, creating new interesting research problems and calling for new ideas and methods that are adapted to the particularities of the MIMO-FBMC/OQAM system. The goal of this paper is to focus on these signal processing problems and provide a concise yet comprehensive overview of the recent advances in this area. Open problems and associated directions for future research are also discussed.Peer ReviewedPostprint (author's final draft

Channel and frequency offset estimation schemes for multicarrier systems

Doutoramento em Engenharia ElectrotécnicaO presente trabalho aborda o problema da estimação de canal e da estimação de desvio de frequência em sistemas OFDM com múltiplas configurações de antenas no transmissor e no receptor. Nesta tese é apresentado o estudo teórico sobre o impacto da densidade de pilotos no desempenho da estimação de canal em sistemas OFDM e são propostos diversos algoritmos para estimação de canal e estimação de desvio de frequência em sistemas OFDM com antenas únicas no transmissor e receptor, com diversidade de transmissão e MIMO. O estudo teórico culmina com a formulação analítica do erro quadrático médio de um estimador de canal genérico num sistema OFDM que utilize pilotos dedicados, distribuidos no quadro transmitido em padrões bi-dimensionais. A formulação genérica é concretizada para o estimador bi-dimensional LS-DFT, permitindo aferir da exactidão da formulação analítica quando comparada com os valores obtidos por simulação do sistema abordado. Os algoritmos de estimação investigados tiram partido da presença de pilotos dedicados presentes nos quadros transmitidos para estimar com precisão os parâmetros pretendidos. Pela sua baixa complexidade, estes algoritmos revelam-se especialmente adequados para implementação em terminais móveis com capacidade computacional e consumo limitados. O desempenho dos algoritmos propostos foi avaliado por meio de simulação do sistema utilizado, recorrendo a modelos aceites de caracterização do canal móvel multipercurso. A comparação do seu desempenho com algoritmos de referência permitir aferir da sua validade. ABSTRACT: The present work focus on the problem of channel estimation and frequency offset estimation in OFDM systems, with different antenna configurations at both the transmitter and the receiver. This thesis presents the theoretical study of the impact of the pilot density in the performance of the channel estimation in OFDM systems and proposes several channel and frequency offset algorithms for OFDM systems with single antenna at both transmitter and receiver, with transmitter diversity and MIMO. The theoretical study results in the analytical formulation of the mean square error of a generic channel estimator for an OFDM system using dedicated pilots, distributed in the transmitted frame in two-dimensional patterns. The generic formulation is implemented for the two-dimensional LS-DFT estimator to verify the accuracy of the analytical formulation when compared with the values obtained by simulation of the discussed system. The investigated estimation algorithms take advantage of the presence of dedicated pilots present in the transmitted frames to accurately estimate the required parameters. Due to its low complexity, these algorithms are especially suited for implementation in mobile terminals with limited processing power and consumption. The performance of the proposed algorithms was evaluated by simulation of the used system, using accepted multipath mobile channel models. The comparison of its performance with the one of reference algorithms measures its validity

Semi-blind channel estimation for multiuser OFDM-IDMA systems.

M. Sc. Eng. University of KwaZulu-Natal, Durban 2014.Over the last decade, the data rate and spectral efficiency of wireless mobile communications have been significantly enhanced. OFDM technology has been used in the development of advanced systems such as 3GPP LTE and terrestrial digital TV broadcasting. In general, bits of information in mobile communication systems are conveyed through radio links to receivers. The radio channels in mobile radio systems are usually multipath fading channels, which cause inter-symbol interference (ISI) in the received signal. The ability to know the channel impulse response (CIR) and Channel State Information (CSI) helps to remove the ISI from the signal and make coherent detection of the transmitted signal at the receiver end of the system easy and simple. The information about CIR and CSI are primarily provided by channel estimation. This thesis is focused on the development of multiple access communication technique, Multicarrier Interleave Division Multiple Access (MC-IDMA) and the corresponding estimation of the system channel. It compares various efficient channel estimation algorithms. Channel estimation of OFDM-IDMA scheme is important because the emphasis from previous studies assumed the implementation of MC-IDMA in a perfect scenario, where Channel State Information (CSI) is known. MC-IDMA technique incorporates three key features that will be common to the next generation communication systems; multiple access capability, resistance to multipath fading and high bandwidth efficiency. OFDM is almost completely immune to multipath fading effects and IDMA has a recently proposed multiuser capability scheme which employs random interleavers as the only method for user separation. MC-IDMA combines the features of OFDM and IDMA to produce a system that is Inter Symbol Interference (ISI) free and has higher data rate capabilities for multiple users simultaneously. The interleaver property of IDMA is used by MC-IDMA as the only means by which users are separated at the receiver and also its entire bandwidth expansion is devoted to low rate Forward Error Correction (FEC). This provides additional coding gain which is not present in conventional Multicarrier Multiuser systems, (MC-MU) such as Code Division Multiple Access (CDMA), Multicarrier-Code Division Multiple Access (MC-CDMA) systems, and others. The effect of channel fading and both cross-cell and intra-cell Multiple Access Interference (MAI) in MC-IDMA is suppressed efficiently by its low-cost turbo-type Chip-by-Chip (CBC) multiuser detection algorithm. We present the basic principles of OFDM-IDMA transmitter and receiver. Comparative studies between Multiple Access Scheme such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), CDMA and IDMA are carried out. A linear Minimum Mean Square Error (MMSE)-based estimation algorithm is adopted and implemented. This proposed algorithm is a non-data aided method that focuses on obtaining the CSI, remove ISI and reduce the complexity of the MMSE algorithm. However, to obtain a better and improved system performance, an improved MMSE algorithm and simplified MMSE using the structured correlation and reduced auto-covariance matrix are developed in this thesis and proposed for implementation of semi-blind channel estimation in OFDM-IDMA communication systems. The effectiveness of the adopted and proposed algorithms are implemented in a Rayleigh fading multipath channel with varying mobile speeds thus demonstrating the performance of the system in a practical scenario. Also, the implemented algorithms are compared to ascertain which of these algorithms offers a better and more efficient system performance, and with less complexity. The performance of the channel estimation algorithm is presented in terms of the mean square error (MSE) and bit error rate (BER) in both slow fading and fast fading multipath scenarios and the results are documented as well

WIMAX 802.16 PHYSICAL LAYER IMPLEMENTATION AND WIMAX COVERAGE AND PLANNING.

Over the last decade, the impact of wireless communication on the way we live and carry out business has been surpassed only by impact of the internet. But wireless communications is still in its infancy and the next stage of its development will be supplementing or replacing network infrastructure that was traditionally wired. The advent and adoption of the computer and the myriad software packages available for it offered the ability to generate a new wave of communication combining art, pictures, music and words into a targeted multimedia presentation. These presentations are large so that is requires higher bandwidth transmission facilities. Coupling this with the need for mobility, the solution would be wireless data delivery putting in consideration the bandwidth request. WiMAX technology is based on the IEEE 802.16 standard, it was only recently when the first IEEE 802.16 based equipment broadband began to enter the market. The additional spectrum, bandwidth and throughout capabilities of 802.16 will remarkably improve wireless data delivery and should allows even more wireless data service areas to be deployed economically. In this Final Year Project, a study about the IEEE 802.16 standard and mainly concentrate on the 802.16 PHY Layer behaviors was performed. A Simulink based model for the 802.16 PHY Layer was built for simulation and performance evaluation of WiMAX. MATLA