Since the prioneering works of Telatar, Foschini and Gans, and Tarokh, Sheshadri and Calderbank, in the mid-90's, space-time communications has been one of the most prolific and promising areas in academic research and technological development in wireless communications. The "holy grail" of early space-time code design was achieving "full diversity‚" at the largest possible coding rate. It took a while before relizing that it is not difficult to design codes that achieve "full diversity" and "full rate" at the same time. Indeed, the problem as stated initially was ill-posed. Zheng and Tse formulated a rigorous "diversity-multiplexing" tradeoff problem, that characterizes the behavior of optimal space-time code families in the high SNR, high spectral efficiency region. Modern space-time coding design has focused on constructing families of codes that attain the optimal diversity-multiplexing tradeoff with low complexity. While the notion of "low complexity" is still somehow vague, several explicit code constructions have been found that provably attain the optimal tradeoff under ML decoding or under lattice decoding.
In this talk I shall review the exciting recent developments of space-time coding design, with particular emphasis on the family of LAST codes, that attains the optimal tradeoff under lattice deocoding. I will stress the generalization of well-known lattice decoding techniques, usually referred to as ``sphere decoders'', with well-known sequential decoding, and point out the advantages of using a slightly modified version of the well-known Fano algorithm to perform lattice decoding. Then, I will focus on the MIMO ARQ channel, and illustrate the optimal diversity-multiplexing-delay tradeoff. It clearly appears that a one-bit feedback couple with a suitable incremental redundancy ARQ scheme is able to dramatically increase diversity for the same multiplexing gain, if some relaxation of the decoding delay requirement is allowed. I shall point out some recent advances in the design of LAST codes and their applications for the space-time hybrid ARQ scheme. Finally, I will illustrate the related problem of transmitting an analog source via a MIMO wireless channel under an end-to-end distortion criterion. I shall present a combination of tradeoff-achieving space-time coding and analog transmission that attains the best possible decay of distortion with SNR for the region of high spectral efficiency. The determination of the optimum decay for the region of low spectral efficiency is an interesting open problem.
Giuseppe Caire was born in Torino, Italy, in 1965. He received the B.Sc. in Electrical Engineering from Politecnico di Torino (Italy), in 1990, the M.Sc. in Electrical Engineering from Princeton University in 1992 and the Ph.D. from Politecnico di Torino in 1994. He was a recipient of the AEI G.Someda Scholarship in 1991, has been with the European Space Agency (ESTEC, Noordwijk, The Netherlands) from May 1994 to February 1995, was a recipient of the COTRAO Scholarship in 1996 and of a CNR Scholarship in 1997.
He has been visiting Princeton University in summer 1997 and Sydney University in summer 2000. He has been Assistant Professor in Telecommunications at the Politecnico di Torino, Associate Professor at the University of Parma, Italy, Professor with the Department of Mobile Communications at the Eurecom Institute, Sophia-Antipolis, France, and he is now professor with the EE Department of the Viterbi School of Engineering, University of Southern California, Los Angeles, CA.
He served as Associate Editor for the IEEE Transactions on Communications in 1998-2001 and as Associate Editor for the IEEE Transactions on Information Theory in 2001-2003. He received the Jack Neubauer Best System Paper Award from the IEEE Vehicular Technology Society in 2003, and the Joint IT/Comsoc Best Paper Award in 2004. Since November 2004 he is member of the Board of Governors of the IEEE Information Theory Society and is Fellow of IEEE.
His current interests are in the field of communications theory, information theory and coding theory with particular focus on wireless applications.
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