From the Publisher:
Multi-carrier modulation, in particular orthogonal frequency division multiplexing (OFDM), has been successfully applied to a wide variety of digital communications applications for several years. Although OFDM has been chosen as the physical layer standard for a diversity of important systems, the theory, algorithms, and implementation techniques remain subjects of current interest. 

This book is intended to be a concise summary of the present state of the art of the theory and practice of OFDM technology. This book offers a unified presentation of OFDM theory and high speed and wireless applications. In particular, ADSL, wireless LAN, and digital broadcasting technologies are explained. 

It is hoped that this book will prove valuable both to developers of such systems, and to researchers and graduate students involved in analysis of digital communications, and will remain a valuable summary of the technology, providing an understanding of new advances as well as the present core technology.

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Multi-Carrier Digital Communications: Theory and Applications of OFDM

Techniques are described for efficiently estimating and compensating for the effects of a communication channel in a multi-carrier wireless communication system. The techniques exploit the fact that the transmitted symbols are drawn from a finite-alphabet to efficiently estimate the propagation channel for multi-carrier communication systems, such systems using OFDM modulation. A transmitter transmits data through a communication channel according to the modulation format. A receiver includes a demodulator to demodulate the data and an estimator to estimate the channel based on the demodulated data. The channel estimator applies a power-law operation to the demodulated data to identify the channel. The techniques can be used in both blind and semi-blind modes of channel estimation.

Channel estimation for wireless ofdm systems

A new kind of "wireless video" is currently entering consumers' homes-digital television. The term digital video broadcasting (DVB) is used as a synonym for digital television in many countries of the world. Whereas one may tend to think that digital television means just a new, digital, form of signal representation not necessarily affecting the information content of what one has always called TV, the truth is that digital television becomes multiple-channel data broadcasting. This article reviews some of the results of the work in the worldwide DVB Project and explains some of the fundamental concepts behind the work of this group. It then concentrates on the terrestrial transmission system (DVB-T) as one example of the many transmission technologies DVB has developed over the last few years. The COFDM modulation scheme which is a key ingredient of DVB-T is described in some detail. The performance of the system is presented. The use of DVB for data broadcasting and the accompanying return channel technologies are explained.

Digital video broadcasting

Orthogonal frequency division multiplexing (OFDM) has been widely adopted in modern wireless communication systems due to its robustness against the frequency selectivity of wireless channels. For coherent detection, channel estimation is essential for receiver design. Channel estimation is also necessary for diversity combining or interference suppression where there are multiple receive antennas. In this paper, we will present a survey on channel estimation for OFDM. This survey will first review traditional channel estimation approaches based on channel frequency response (CFR). Parametric model (PM)-based channel estimation, which is particularly suitable for sparse channels, will be also investigated in this survey. Following the success of turbo codes and low-density parity check (LDPC) codes, iterative processing has been widely adopted in the design of receivers, and iterative channel estimation has received a lot of attention since that time. Iterative channel estimation will be emphasized in this survey as the emerging iterative receiver improves system performance significantly. The combination of multiple-input multiple-output (MIMO) and OFDM has been widely accepted in modern communication systems, and channel estimation in MIMO-OFDM systems will also be addressed in this survey. Open issues and future work are discussed at the end of this paper.

Channel Estimation for OFDM

In mobile reception, the reliability of orthogonal frequency division multiplexing (OFDM) is limited because of the time-varying nature of the channel. This causes intercarrier interference (ICI) and increases inaccuracies in channel tracking. We model the ICI using derivatives of the channel amplitude. This allows us to design a relatively simple receiver scheme that iteratively cancels the ICI. The design of the canceler aims at maximizing the signal-to-noise-plus-ICI ratio at the detector input. We also propose a new channel estimator, and we show that it achieves reliable mobile reception in practical situations that are relevant to terrestrial Digital Video Broadcasting (DVB-T). Extensive simulations for a receiver with one or two antennas show that a small number of iterations between ICI cancellation and channel estimation allow a reliable reception at vehicle speeds above 100 km/h.

/pdf/iterative-interference-cancellation-and-channel-estimation-2occkailuq.pdf

Iterative interference cancellation and channel estimation for mobile OFDM

The paper describes a novel channel estimation scheme (identified as CD3, coded decision directed demodulation) for coherent demodulation of OFDM (orthogonal frequency division multiplex) signals making use of any constellation format (e.g. QPSK, 16 QAM, 64 QAM). The structure of the CD3-OFDM demodulator is described, based on a new channel estimation loop exploiting the error correction capability of a forward error correction (FEC) decoder and frequency and time domain filtering to mitigate the effects of noise and residual errors. In contrast to the conventional coherent OFDM demodulation schemes, CD3-OFDM does not require the transmission of a comb of pilot tones for channel estimation and equalisation, therefore yielding a significant improvement in spectrum efficiency (typically between 5% and 15%). The performance of the system with QPSK and 64 QAM modulations is analysed by computer simulations, on AWGN and frequency selective channels. The results indicate that CD3-OFDM allows to achieve C/N performance similar to coherent demodulation with pilot tones, when the same channel coding and modulation scheme is adopted. Otherwise, when the additional capacity is exploited to increase the FEC redundancy instead of the useful bit-rate, CD3 can offer significant C/N advantages (typically from 2 to 5 dB depending on the channel characteristics). Therefore CD3-OFDM can be suitable for digital television broadcasting services over selective radio channels.

CD3-OFDM: a new channel estimation method to improve the spectrum efficiency in digital terrestrial television systems

The paper analyses the coverage achievable in single frequency networks (SFN) by the European system for digital video broadcasting on terrestrial channels (DVB-T), using two different receiver structures: the conventional coherent demodulation method using the pilot tones inserted in the OFDM (orthogonal frequency division multiplexing) spectrum and the new scheme proposed by RAI, based on coded decision directed demodulation (CD3-OFDM) combined with a new lock-in algorithm. The first structure is characterised by a rapid performance degradation for echoes outside the guard interval, while the second shows a more gradual degradation, like the DAB (digital audio broadcasting) system. The performance evaluation based on theoretical analysis, software simulations and hardware laboratory tests, shows the significant coverage improvement offered by the gradual degradation CD3-OFDM algorithm, especially in the cases of omni-directional antennas, medium to high bit-rates and transmitter distances exceeding 40 km.

http://ieeexplore.ieee.org/iel3/4959/13639/00626912.pdf

An advanced algorithm for improving DVB-T coverage in SFN

The general concepts of the system for digital television transmission by satellite developed within the European DVB (digital video broadcasting) project and standardised by ETSI (European Telecommunications Standards Institute) are described. The system, named DVB-S, is intended to provide DTH (direct-to-home) multi-programme TV services in the BSS (broadcasting satellite service) and FSS (fixed satellite service) bands and is addressed to consumer IRDs (integrated receiver decoders), as well as collective antenna systems (SMATV, satellite master antenna TV) and cable television head-end stations, with a likelihood of remodulation. The exploitation of the multiplex flexibility allows the use of the transmission capacity for a variety of TV service configurations. The use of flexible and advanced error protection techniques, based on the concatenation of Reed-Solomon and convolutional codes (with Viterbi decoding), allows optimum adaptation to different satellite transponder characteristics, i.e. bandwidth and power, providing high service quality and availability with small receiving antennas. For example, in climatic zone E (in Europe) on a 33 MHz transponder a data-rate of 38.1 Mbit/s can be transmitted, adequate to provide five standard definition TV programmes (SDTV) or, alternatively three to four enhanced definition programmes (EDTV), while ensuring 99.90% service availability (in the average year) with 50-cm receiving antenna within the 51 dBW EIRP (equivalent isotropic radiated power) service area contour. >

The European system for digital multi-programme television by satellite

The latest developments in VLSI (very–large scale integration) technology have significantly contributed to the rapid emergence of digital image/video compression techniques in broadcast and information–oriented applications; optical fibre technology allows broadband end–to–end connectivity at very high bit–rates including digital video capabilities; even the narrow–band terrestrial broadcast channels in the VHF/UHF bands (6–7 MHz and 8 MHz) are under investigation, in the USA [1] and in Europe [2], for the future introduction of digital television services.

https://tech.ebu.ch/docs/techreview/trev_256-cominetti.pdf

M. Visintin

Papers

CD3-OFDM: a new channel estimation method to improve the spectrum efficiency in digital terrestrial television systems

An advanced algorithm for improving DVB-T coverage in SFN

The European system for digital multi-programme television by satellite

Digital multi-programme TV/HDTV by satellite

Systèmes d'émission à large bande de TVHD numérique. Performances des techniques évoluées de modulation et de codage canal