Multicarrier transmission techniques

Abstract

The issue in hand presents a selection of papers of the > which was held at Hamburg University of Technology, Hamburg, Germany, March 20-21, 1996. The workshop was organized by the Telecommunication Research Group and its head Norbert J. Fliege from the same university. About 50 scientists from 8 countries attended the workshop. At the end of the workshop it was clearly stated that in the European scientific community there is a significant interest in multirate digital signal processing with applications like filter banks, subband coding, wavelet techniques and multicarrier data transmission. Thus, the attendees agreed to continue the workshop in the future and T. Saramiiki from Tampere University in Finland agreed to organize the next edition of the workshop. During the two days of the workshop 7 sessions with 24 plenary lectures were provided. The sessions were dedicated to filter banks, wavelet and Gabor theory, image and video coding, asymmetric digital subscriber loops, and multicarrier data transmission. As conclusions of the workshop, two main applications of multirate digital signal processing were observed : subband coding of audio, video, and image signals on the one hand and multicarrier telecommunication techniques on the other hand. Three further papers of the issue in hand are selected from the ~ > which took place at Technical University of Braunschweig, Braunschweig, Germany, September 10-11, 1996. The meeting was organized by H. Rohling and his research group. The special issue in hand is focused on multicarrier transmission techniques which is possibly the most important part of multirate digital signal processing concerning practical applications and economical outcome. One of the most interesting multicarrier transmission methods, namely OFDM (orthogonal frequency division multiplexing) or DMT (discrete multi tone) have proved to be very efficient compared to the single carrier approach in case of critical transmission channels. The new European DAB (digital audio broadcasting) and DVB (digital video broadcasting) are based on OFDM. Furthermore, new systems utilizing OFDM for the data transmission via twisted pairs at a rate of 64 kbit/s and 2 Mbit/s are announced. The special issue on multicarrier transmission techniques provides 10 papers presenting advanced methods and improved performance results. Corresponding to the state of the art, OFDM problems are in the foreground of discussions. There are 3 papers aimed on avoiding the guard intervall of OFDM, but by different methods. V. Ddmoulin and M. Pdcot from Thomson multimedia R&D, France, solve this problem by means of vector equalization. Another approach with blind equalization is presented by M. de Courville, P. Duhamel from Tdldcom-Paris, France, and P. Madec and J. Palicot from CNET-CCETT, Cesson-S6vign6, France. The third approach, namely by fractionally spaced linear equalizers is proposed by L. Vandendorpe from UCL Communications and Remote Sensing Laboratory, Louvain-la-Neuve, Belgium. One of the most interesting tasks in advanced multicarrier transmission techniques is the equalization of the channel response. There are 3 papers considering this problem. Two of them are based on a structure with equalizers in the subbands, the first one is discussed by L. Qin and M. G. Bellanger from CNAM Paris, France, the second one by T. Wiegand and N. J. Fliege from Hamburg University of Technology, Germany. In the third paper presented by G. ROsel from Hochschule fiir Technik und Wirtschaft, Dresden, Germany, and N. J. Fliege, a band-pass equalizer at the input of the data receiver is investigated. The remaining 4 papers deal with important special problems of OFDM systems. Coherent and incoherent detection in coded OFDM systems is compared by H. Rohling and T. May from Technical University of Braunschweig, Germany. The reduction of peak-to-average power ratio is adressed by S. H. Miiller, R. W. Biiuml, R. F. H. Fischer and J. B. Huber from University Erlangen-Niirnberg, Germany. Clock recovery for synchronous DMT data transmission is analyzed by G. Dickmann, S. Trautmann and N.J. Fliege from Hamburg University of Technology, Germany. Finally, the effects of trellis shaping in OFDM systems are considered by M. Bossert and A. Donder from University of Ulm, Germany. I would like to thank all authors for preparing their accurate and instructive papers which, regarded all together, hopefully provide an interesting and useful issue of the Annals of Telecommunications.