Multi-Carrier Techniques for Broadband Wireless Communications - A Signal Processing Perspective

Abstract

PrefaceThe demand for multimedia wireless communications is growing today at an explosive pace. One common feature of many current wireless standards for high-rate multimedia transmission is the adoption of a multicarrier air interface based on either orthogonal frequency-division multiplexing (OFDM) or orthogonal frequency-division multiple-access (OFDMA). The latest examples of this trend are represented by the IEEE 802.11 and IEEE 802.16 families of standards for wireless local area networks (WLANs) and wireless metropolitan area networks (WMANs). Although the basic principle of OFDM/OFDMA is well established among researchers and communication engineers, its practical implementation is far from being trivial as it requires rather sophisticated signal processing techniques in order to fully achieve the attainable system performance. This book is intended to provide an accessible introduction to OFDMbased systems from a signal processing perspective. The first part provides a concise treatment of some fundamental concepts related to wireless communications and multicarrier systems, whereas the second part offers a comprehensive survey of recent developments on a variety of critical design issues including synchronization techniques, channel estimation methods, adaptive resource allocation and practical schemes for reducing the peakto-average power ratio of the transmitted waveform. The selection and treatment of topics makes this book quite different from other texts in digital communication engineering. In most books devoted to multicarrier transmissions the issue of resource assignment is not discussed at all while synchronization and channel estimation are only superficially addressed. This may give the reader the erroneous impression that these tasks are rather trivial and the system can always operate close to the limiting case of ideal synchronization and channel estimation. However, as discussed Multi-Carrier Techniques for Broadband Wireless Communicationsin this book, special design attentions are required for successfully accomplishing these tasks. In many cases, the trade-off between performance and system complexity has to be carefully taken into consideration in the practical implementation of multicarrier systems. Most of the presented material originates from several projects and research activities conducted by the authors in the field of multicarrier transmissions. In order to keep the book concise, we do not cover advanced topics in multiple-input multiple-output (MIMO) OFDM systems as well as latest results in the field of resource assignment based on game theory. Also, we do not include a description of current wireless standards employing OFDM or OFDMA which are available in many other texts and journal papers.The book is written for graduate students, design engineers in telecommunications industry as well as researchers in academia. Readers are assumed to be familiar with the basic concepts of digital communication theory and to have a working knowledge of Fourier transforms, stochasti...

Enhanced OFDM for fragmented spectrum use in 5G systems

“…The orthogonality is maintained efficiently using inverse fast Fourier transform (IFFT) block. The modulated OFDM signal is represented as follows : where N is the IFFT length, x k , n ∈{ x 0, n , x 1, n ,..., x N − 1, n } is zero mean i.i.d. subcarrier sample sequence which forms the n th OFDM symbol and T u is the time duration of useful samples in OFDM symbols.…”

Effects of Filters on the Performance of DVB-T Receiver

“…OFDM has numerous advantages over other digital modulation schemes. The main advantage of OFDM is that it can minimize the Inter Symbol Interference (ISI), which is originated from the multipath signal propagation [14] as mentioned earlier. Hence, it can support a very high data rate.…”

Comparison of distributed space frequency block coding schemes in broadband multi-node cooperative relay networks with PAPR reduction

“…The peak power can theoretically be up to N times larger than the average power level. As a result of this problem, the system needs more bits to cover a potentially broad dynamic range and the transmitted signal may suffer significant spectral spreading and in-band distortion as a con sequence of intermodulation effects induced by a nonlinear power amplifier [2]. In MIMO-OFDM systems PAPR be comes even more important since there are multiple transmit antennas each of which would require its own radio frequency 978-1-4577-0274-7/11/$26.00 ©2011 IEEE (RF) power amplifier and digital-to-analog converter (DAC).…”

“…A number of solutions to the PAPR problem of OFDM have been proposed. These approaches can be essentially divided into two classes [2]. The first one is characterized by the fact that, although the PAPR of the transmit signal is reduced, the signal remains undistorted.…”

“…However, in general amplitude clipping gives rise to in-band distortion as well as out-of-band leakage. To overcome the out-of-band problem, oversampling before clipping and then filtering can be used [2]. To mitigate the harmful effects of clipping, we utilise the IAR technique proposed in [3] [4].…”