Date: February 24, 2009 (Tuesday)
Time: 2:00pm
Place: 202 ECEC, NJIT

About the Presenter:

Amir Laufer is a Ph. D student in Electrical Engineering at the Center of Wireless Communication and Signal Processing Research (CWCSPR) at New Jersey Institute of Technology (NJIT) with the guidance of Prof. Bar-Ness. His research interests are Space Time Coding (STC), Hybrid Network and Modulation Classification. He received his B.S.  (05) and M.S  (06) both in Electrical Engineering from Tel Aviv University, Israel. His Master Thesis topic was “Game theoretic aspects of distributed spectrum cooperation for DSL networks” and dealt with a form of the “Prisoner’s Dilemma” that can be formed when a common resource of a system is handled without any regulations.   

About the Talk:

Space time codes (STC) have been shown to be used well with the Multiple Input Multiple Output (MIMO) channel. The Orthogonal STC (OSTC) family of codes is known to achieve full diversity as well as very simple implementation of the Maximum Likelihood (ML) decoder. However, it was proven that with a complex symbol constellation one cannot achieve a full rate code when the number of transmitting antennas is larger than 2. In order to tackle this inherent rate loss of the OSTC we suggest what we term the "row elimination" method. With this transmission method only part of the code word is transmitted. By eliminating one or more rows (which corresponds to the time in the space-time code structure) the rate is increasing. Obviously, the remaining code word is not orthogonal anymore hence requires complex ML decoder realization. Therefore, another sub-optimal decoding scheme is adopted such as the Zero Forcing (ZF) decoder. Since the ZF decoder involves the inversion of the channel matrix the computational complexity is still relatively high. To that end we propose a new decoding scheme which contains two steps - at the first step the non-transmitted part is estimated at the receiver while at the second step the transmitted symbols are retrieved based on the received and the estimated data. It can be shown that this scheme is equal to the ZF decoder but with less computational overhead. Moreover, we found a method to generate new OSTC for which, applying the suggested transmission and decoding schemes, results in a full rate and linear complexity for the ZF decoder for any number of transmit antennas. It can be shown that when the transmitter knows the strongest channel (through minimal feedback) the performance of the suggested schemes is better than the performance achieved by the use of OSTC or even Quasi-OSTC (QSTC) codes with the same rate and power budget.

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Note: All ECE MS thesis defense and Ph.D. dissertation (proposal) defense are counted towards ECE791.