University of Southern California WiDeS - Wireless Devices and Systems Group The USC Andrew and Erna Viterbi School of Engineering USC

Dr. Molisch regularly gives tutorials at international conferences on the following topics:


UTRAWIDEBAND SYSTEMS


Ultra-wide bandwidth (UWB) transmission systems have gained increasing interest in the scientific, commercial, and military sectors over the last decade. Wide bandwidth provides fine delay resolution, making UWB a viable candidate for communications and accurate positioning in dense multipath environments. Currently, UWB transmission systems are being developed for communications, localization, and sensor networks because they potentially allow low-cost production and reuse of (already occupied) spectrum. UWB also has applications in military and homeland security operations because it provides low probability of detection as well as anti-jam capabilities.

Interest in UWB systems has intensified recently due to the ruling by the US Federal Communications Commission (FCC) concerning UWB emission masks. This ruling opens the way for coexistence with traditional and protected radio services and allows the potential use of UWB transmission without allocated spectrum. Standardization bodies (like IEEE 802.15) have developed standards for UWB systems and companies are announcing products. In this tutorial, we will give a technical overview that will allow the attendants to distinguish between commercial hype and the true technical possibilities.

The tutorial will start with a description of the principles of UWB and the frequency regulations and spectral masks that determine the operating parameters of UWB in different regions of the world. Next, we outline the various applications, which range from communications in low-power sensor networks to precision geolocation to extremely-high-data-rate communications for consumer electronics.

Next, we describe UWB propagation channels, which have several distinctive characteristics that not only set them apart from regular wireless channels, but also influence system performance. The different transmission schemes used in UWB systems are described next. We concentrate on time-hopping impulse radio, which is not only the method of choice for low-power transmission schemes, but also is the most interesting from a scientific point of view. We will also briefly describe multi-band OFDM schemes, which are used for high-data-rate communications, as well as direct-sequence spread spectrum and frequency hopping.

We then move to a description of UWB-based ranging and geolocation systems. The large bandwidth of UWB systems allows, in principle, very high ranging accuracy. However, multipath propagation, noise, as well as timing jitter lead to particular problems. We discuss these issues as well as solutions.

Last, but not least, we discuss implementation issues like signal acquisition, channel estimation, and antenna design. We round off the tutorial with the two most important standards, WiMedia, and IEEE 802.15.4a.

MULTIPLE ANTENNA SYSTEMS FOR COMMUNICATIONS - Smart antennas, MIMO systems, and the propagation channels they operate in


Smart antennas and MIMO (multiple-input multiple-output) systems utilize multiple antennas at one and at both wireless link ends, respectively. These techniques can be used to increase the capacity of mobile radio systems, both for upgrading second-generation systems and for use in third- and fourth generation systems. Thus, multi-antenna systems have attracted enormous interest and a lot of effort has been spent for its system development and standardization. The tutorial will give a comprehensive overview over all relevant aspects of smart antenna and MIMO systems.

The mobile radio channel, especially its directional nature defined by the directions-of-arrival and directions-of-departure of the waves propagating from transmitter to receiver, determines the performance of multi-antenna systems. Therefore, we start out with an introduction of spatial channel sounding techniques forming the basis for spatial channel measurements and spatial channel characterization. We present measurement results of the directional channel properties as seen from the base station and from the mobile terminal only, as well as measurements of the double-directional propagation characteristics. We then explain how these measurement results can be utilized and included in spatial channel models, which are required for the design and development of adaptive antenna and MIMO systems.

Next, we describe transceiver structures and algorithms for smart antennas at one link end. After an introduction to the basic smart antenna technology, we describe different adaptation techniques for multi-antenna reception in detail. Thereby, we consider temporal reference, spatial reference as well as blind adaptation algorithms and present their performance in different propagation conditions. Moreover, the fundamental differences of reception and transmission using several antennas will be explained and transmission strategies including downlink beamforming and transmission diversity will be derived. The more practical aspects of roll-out and capacity of smart antenna base stations – especially in the context of 3G systems - will complete the considerations of multiple antennas at one link end.

Next, we present the two operation modes of MIMO systems applying multiple antennas for transmission and reception: diversity enhancement, and BLAST-like schemes. In the former case, the multiple antennas at both link ends are used to provide a high degree of diversity, resulting in a high-quality link. We explain what diversity degree and beamforming gain can be achieved in different types of wireless channels. Then, we describe BLAST schemes where independent data streams are sent from the different transmit antennas, and the multiple receive antennas are used to receive and separate those different data streams. We show how the capacity of these systems can increase linearly with the number of transmit and receive antennas. Different BLAST implementations are explained, and their advantages and drawbacks are discussed. Finally, we demonstrate the principles of space-time codes, and show how those can be applied for diversity and capacity increase. A discussion of interference-limited MIMO systems, and of waterfilling schemes, will round off the presentation.


4G SYSTEMS


Wireless communications services are becoming ever more popular, due to improvements in technology and the emergence of new applications. With current 3G and WiFi systems bursting at the seams, new systems with higher peak data rates and improved spectral efficiency are required. As a consequence, several new “next-generation” standards are currently emerging, the most important of which are 3GPP-LTE, Advanced WiMAX, and IEEE 802.11n. They will almost certainly be part of the 4G “IMT-Advanced” family of standards that the ITU (International Telecommunications Union) is currently selecting.  This tutorial will provide up-to-date overview of 4G technologies and standard development.

The IMT-Advanced standards have a number of common features, namely that they are all based on MIMO-OFDM (multiple-input – multiple-output orthogonal frequency division multiplexing) physical layer technology, use advanced coding schemes like turbo code/LDPC, need inter-cell interference coordination, and improve the efficiency of the medium access control (MAC) layer. In our tutorial, we will compare how those technologies are applied in the different standards. Based on our first-hand knowledge gained during our participation of and contribution to all three standards, we will provide a systematic and detailed overview of the keys to the future of broadband wireless communications.


Previous Tutorials


2009

T-27    A. F. Molisch, N. B. Mehta, and J. Tao,  “IMT-Advanced Systems: Enabling Technologies and Standardizations “    
Half-day tutorial at ICC, Dresden, Germany

2008

T-26 A. F. Molisch, “MIMO systems and spatial channels“
Half-day tutorial at MILCOM, San Diego, USA

T-25 A. F. Molisch and M. Z. Win, “Ultra-wide-bandwidth systems”
Half-day tutorial at MILCOM, San Diego, USA

T-24 A. F. Molisch, “MIMO propagation channels“
Half-day tutorial at URSI General Assembly, Chicago, IL, USA

T-23 A. F. Molisch, “MIMO systems and spatial channels“
Full-day tutorial at IEEE Antennas and Propagation Symposium, San Diego, CA, USA

T-22 M. Z. Win and A. F. Molisch, “Ultra-wide-bandwidth systems”
Half-day tutorial at IEEE International Conference on Communications, Beijing, China

2007

T-21 A. F. Molisch, “Multiple-antenna systems “
Full-day tutorial at IEEE Antennas and Propagation Symposium, Honululu, HI, USA

2006

T-20 A. F. Molisch, E. Bonek, and F. Tufvesson, “Measurement and modelling of wireless propagation channels for MIMO and UWB “
Full-day tutorial at joint ACORN-NEWCOM workshop, Vienna, Austria

2005

T-19 A. F. Molisch, „Ultrawideband propagation channels“
Half-day tutorial at IEEE International Conference on Ultrawideband, Zurich, Switzerland

2004

T-18 M. Z. Win and A. F. Molisch, "Ultrawideband systems",
Half-day tutorial at IEEE Globecom ‚04, Dallas, USA

T-17 E. Bonek, K. Hugl, A. F. Molisch, and W. Weichselberger, „Smart antennas and MIMO systems“
Full-day tutorial at IEEE ICC ‚04, Paris, France

T-16 M. Z. Win and A. F. Molisch, "Ultrawideband systems",
Half-day tutorial at IEEE ICC ‚04, Paris, France

2003

T-15 M. Z. Win and A. F. Molisch, "Ultrawideband systems",
Half-day tutorial at IEEE Globecom ‚03, San Francisco, USA

T-14 A. F. Molisch, W. Weichselberger, and E. Bonek, “Spatial channels (including MIMO)“
Half-day tutorial at IEEE WPMC Yokosuka, Japan

T-13 M. Z. Win and A. F. Molisch, "Ultrawideband systems",
Half-day tutorial at IEEE Consumer Electronics Conf. Los Angeles ‚03, USA


T-12 A. F. Molisch, A. Kuchar, J. Laurila, and E. Bonek, “Spatial channels and smart antennas”:
Half-day tutorial at IEEE VTC fall 2003, Orlando, USA

2002

T-11 A. F. Molisch, J. Laurila, K. Hugl, and E. Bonek, “MIMO systems”:
Half-day tutorial at IEEE WPMC ‚02 Hawaii, USA

T-10 A. F. Molisch, A. Kuchar, J. Laurila, and E. Bonek, “Spatial channels and smart antennas”:
Full-day tutorial at IEEE PIMRC 2002, Lisbon, Portugal

T-09 A. F. Molisch and H. Asplund, “The COST259 channel model“
Half-day tutorial, COST 273 workshop, Helsinki, Finland

T-08 A. F. Molisch, A. Kuchar, J. Laurila, and E. Bonek, “Spatial channels and smart antennas”:
Full-day tutorial at IEEE VTC’02, Birmingham, USA

T-07 A. F. Molisch, A. Kuchar, J. Laurila, and E. Bonek, “Spatial channels and smart antennas”:
Half-day tutorial at IEEE ICC’02, New York, USA

2001

T-06 A. F. Molisch, A. Kuchar, J. Laurila, and E. Bonek, “Spatial channels and smart antennas”:
Full-day tutorial at IEEE VTC’01, Atlantic City, USA

T-05 A. F. Molisch, A. Kuchar, J. Laurila, M. Toeltsch, M. Steinbauer, and E. Bonek, “Measurement and simulation of spatial mobile radio channels”,
Online Symposium for Electrical Engineers, www.techonline.com

T-04 A. F. Molisch, A. Kuchar, J. Laurila, and E. Bonek, “Spatial channels and smart antennas”:
Full-day tutorial at EPMCC, Vienna, Austria

2000

T-03 A. F. Molisch, A. Kuchar, J. Laurila, and E. Bonek, ”Smart antennas in mobile communications”,
Online Symposium for Electrical Engineers, fall 2000, www.techonline.com

T-02 A. F. Molisch, A. Kuchar, J. Laurila, and E. Bonek, “Spatial channels and smart antennas”:
Full-day tutorial at IEEE PIMRC 2000, London, UK

1999

T-01 A. F. Molisch, A. Kuchar, J. Laurila, and E. Bonek, “Spatial channels and smart antennas”:
Full-day tutorial at IEEE VTC’99, Amsterdam, Netherlands