S. Kaiser - Böcker

The benefits and success of multi-carrier (MC) modulation on one side and the flexibility offered by the spread spectrum (SS) technique on the other side has motivated many researchers to investigate the combination of both techniques since 1993. This combination, known as multi-carrier spread-spectrum (MC-SS), benefits from the main advantages of both systems and offers high flexibility, high spectral efficiency, simple detection strategies, narrow-band interference rejection capability and more. The basic principle of this combination is straightforward: the spreading is performed as direct sequence spread-spectrum (DS-SS) but instead of transmitting the chips over a single carrier, several sub-carriers could be employed. The MC modulation and demodulation can easily be realized in the digital domain by performing IFFT and FFT operations. The separation of the users' signals could be performed in the code domain. This means that the MC-SS system performs the spreading in the frequency domain, which allows for simple signal detection strategies. Since 1993, MCSS has been deeply studied and new alternative solutions have been proposed.Meanwhile, deep system analysis and comparison with DS-CDMA have been performed that show the superiority of MC-CDMA. The aim of this volume is to edit the ensemble of contributions and research results in this field presented during three days at the Third International Workshop on Multi-Carrier Spread-Spectrum (MC-SS) and Related Topics, held in Oberpfaffenhofen, Germany.

The benefits and success of multi-carrier (MC) modulation on one hand, and the flexibility offered by spread spectrum (SS) techniques on the other, have, since 1993, motivated many researchers to investigate the combination of both techniques, known as multi-carrier spread-spectrum (MC-SS). This combination benefits from the main advantages of both systems and offers high flexibility, high spectral efficiency, simple detection strategies, narrow-band interference rejection capability, and so on. The basic principle of this combination is straightforward: the spreading is performed as direct sequence SS (DS-SS) but instead of transmitting the chips over a single carrier, several sub-carriers can be employed. The MC modulation and demodulation can easily be done in the digital domain by performing IFFT and FFT operations. The separation of the users' signals can be performed in the code domain. This means that the MC-SS system performs the spreading in the frequency domain, which allows for simple signal detection strategies. Since 1993, MC-SS has been extensively researched and new alternative solutions have been proposed.Meanwhile, deep system analyses and comparisons with DS-CDMA have been performed that show the superiority of MC-CDMA. This text, which consists of seven parts, contains a collection of papers, dealing with all aspects of MC-SS, presented at the Second International Workshop on Multi-Carrier Spread-Spectrum (MC-SS) and Related Topics, held from September 15-17, 1999 in Oberpfaffenhofen, Germany. It should be of value as a reference for researchers and practitioners working in the area of wireless communications and networks.

The key of a successful approach to the complex issue of designing wireless terminals for present and future communication systems (usually addressed to as '3rd Generation and beyond') lies in a single 'magic' word: multidisciplinarity. This was actually the philosophy which inspired and drove a fruitful teamwork performed at the University of Pisa (Italy) under the auspices of the European Space Agency (ESA) with the goal of developing a digital receiver for CDMA mobile communications. The most challenging issue of the project was the implementation into a single ASIC device of an advanced detector for multi-user CDMA signals featuring interference mitigation capability. The whole design process, starting from system specifications down to final hardware testing, required quite a demanding and synergic effort, involving telecom engineers on one side and electronic designers on the other. The development and the achievements of the project gave the authors the cue for writing this book whose contents represents the lesson learnt from such an interdisciplinary research activity. An Experimental Approach to CDMA and Interference Mitigation was written with the admittedly ambitious in

Postmemories of Terror focuses on how young Argentineans remember the traumatic events of the military dictatorship (1976-83). This fascinating work is based on oral histories with sixty-three young people who were too young to be directly victimized or politically active during this period.

Stefan Kaiser Khaled Fazel Radio System Design German Aerospace Center (DLR) Marconi Communications lnstitute of Communications and Navigation D-71522 Backnang, Germany D-82234 Wessling, Germany We are currently observing that frequency spectrum is a limited and valuable resource for wireless mobile communications. A good example can be observed among European network operators for the prices to pay for frequency bands for UMTS/IMT2000. Keeping this in mind, the fIrst goal when designing future wireless communication systems has to be the increase in spectral effIciency by allowing higher flexibility for the system design and deployment. The development in digital communications in the past years has enabled effIcient modulation and coding techniques for robust and spectral effIcient data, speech, audio and video transmission. Here, we should mention two interesting and successful techniques. These are the multi-carrier modulation (e. g. OFDM) and the spread spectrum technique (e. g. DS-CDMA). During the last decade of this millennium the technique of multi-carrier transmission for wireless broadband multimedia applications has received wide interest. Its fIrst great success was in 1990 as it was selected for the European Digital Audio Broadcasting (DAB) standard. Its further prominent success was in 1995 and 1998 as it was selected as modulation scheme for the European Digital Video Broadcasting (DVB-T) standard and in three broadband wireless indoor standards, namely European ETSI-HIPERLAN/2, American IEEE-802. 11a and Japanese MMAC, respectively.

Khaled Fazel Stefan Kaiser Digital Microwave Systems German Aerospace Center (DLR) Bosch Telecom GmbH Institute for Communications Technology D-71522 Backnang, Germany D-82234 Wessling, Germany In this last decade of this millennium the technique of multi-carrier transmission for wireless broadband multimedia applications has been receiving wide interests. Its first great success was in 1990 as it was selected in the European Digital Audio Broadcasting (DAB) standard. Its further prominent successes were in 1995 and 1998 as it was selected as modulation scheme in the European Digital Video Broadcasting (DVB-T) and in three broadband wireless indoor standards, namely ETSI-Hiperlan-II, American IEEE-802. 11 and Japanese MMAC, respectively. The benefits and success of multi-carrier (MC) modulation in one side and the flexibility offered by spread spectrum (SS) technique in other hand motivated many researchers to investigate the combination of both techniques, known as multi-carrier spread-spectrum (MC-SS). This combination benefits from the main advantages of both systems and offers high flexibility, high spectral efficiency, simple detection strategies, narrow­ band interference rejection capability, etc. . The basic principle of this combination is straightforward: The spreading is performed as direct SS (DS-SS) but instead of transmitting the chips over a single sequence carrier, several sub-carriers could be employed. As depicted in Figure 1, after spreading with assigned user specific code of processing gain G the frequency mapping and multi-carrier modulation is applied. In the receiver side after multi-carrier demodulation and frequency de-mapping, the corresponding detection algorithm will be performed.