The talk will give a short introduction to Centre for Wireless Communications (CWC), University of Oulu, Oulu, Finland research activities related to multiple-input multiple-output (MIMO) receiver algorithms and architectures. Particular emphasis is given on two main topics: lattice reduction (LR) based linear equalizers for coded MIMO transmission, and implementation complexity of two novel list sphere detector (LSD) algorithms.

The use of lattice reduction has been shown to be a very effective method for signal detection in multiple antenna systems. The performance of the sub-optimal soft output maximum a posteriori (MAP) detector with lattice reduction is studied in multiple-input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) system. We propose two polynomial-time methods to generate the desired size candidate list in the reduced lattice. The sub-optimal soft-output MAP detector with these list generation methods provides a near-optimal performance in uncorrelated MIMO-OFDM systems, but with significantly reduced computational complexity.

The complexity and performance of two novel list sphere detector (LSD) algorithms are studied and evaluated in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system. The LSDs are based on the K-best and the Schnorr-Euchner enumeration (SEE) algorithms. The required list sizes for LSD algorithms are determined for a 2£2 system with 4- quadrature amplitude modulation (QAM), 16-QAM, and 64-QAM. The complexity of the algorithms is compared by studying the number of visited nodes per received symbol vector by the algorithm in computer simulations. The SEE based LSD algorithm is found to be a less complex and feasible choice for implementation compared to the K-best based LSD algorithm.

Host: Joseph Cavallaro

Biography of Markku Juntti:
Markku Juntti received his M.Sc. (Tech.) and Dr.Sc. (Tech.) degrees in Electrical Engineering from University of Oulu, Oulu, Finland in 1993 and 1997, respectively.

Dr. Juntti has been with Telecommunication Laboratory and Centre for Wireless Communications, University of Oulu in 1992-98. In academic year 1994-95 he was a Visiting Scholar at Rice University, Houston, Texas. In 1999--2000 he was with Nokia Networks. Dr. Juntti has been a Professor of Telecommunications at University of Oulu since 2000. His research interests include communication and information theory, signal processing for wireless communication systems as well as their application in wireless communication system design. He is an author or co-author in some 150 papers published in international journals and conference records as well as in book WCDMA for UMTS published by Wiley.

Dr. Juntti is an Associate Editor for IEEE Transactions on Vehicular Technology. He was Secretary of IEEE Communication Society Finland Chapter in 1996-97 and the Chairman for years 2000-01. He has been Secretary of the Technical Program Committee (TPC) of the 2001 IEEE International Conference on Communications (ICC'01), and the Co-Chair of the Technical Program Committee of 2004 Nordic Radio Symposium and IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2006).