Detection And Space-time Coding In The MIMO System With Asynchronous Transmission Mode

The Vertical Bell Laboratories architecture of layered space-time (V-BLAST) system with asynchronous transmission mode is first proposed in IEEE Transaction on Vehicle Technology of 2007, and it has a very impressive property: it can achieve full diversity using a simple Zero Forcing (ZF) detection, by which the conventional V-BLAST system with synchronous transmission mode cannot be characterized. Therefore it is a very potential space-time code.The strategy of the asynchronous multiple antenna transmission make samples at receiver interrelated, and different method of sampling results in different relationship among all samples, therefore any kind of sampling method cannot be pre-selected as a priori information during deriving the optimal detection algorithm under different criteria. Besides, how to apply the non-linear detection algorithms in the V-BLAST system with asynchronous transmission mode is also an important problems to solve. Finally, considering that the V-BLAST system with asynchronous transmission mode can achieve full diversity using a simple ZF detection, whether it is feasible to find a good and simple architecture of space-time code in the multiple input multiple output (MIMO) system with asynchronous transmission.This thesis focuses on the problem mentioned above and consists of the following aspects: the optimal linear detection and non-linear detection in the V-BLAST system with asynchronous transmission mode and the key characteristic and space-time coding of the MIMO system with asynchronous transmission mode.First, considering the sampling method as a part of the optimal detection, the optimal ZF and Minimum Mean Square Error (MMSE) detection algorithms are derived directly from the original continuous, unsampled signals at receive antennas by the methods of functional analysis. The diversity analyses demonstrate both of them can achieve full diversity in the V-BLAST system.Second, a successive interference cancellation (SIC) architecture is presented that intuitively derived form mathematical expression of the sampled output vector of a bank of matched filters at each receive antenna. However, it can not employ the optimal detection order to minimize the propagation of errors from one step of detection to the next and actually consumes extra energy of the previously detected signals to recover a signal. Therefore an improved SIC architecture is subsequently proposed to overcome the two shortcomings mentioned above and an ordered successive interference cancellation (OSIC) based on this improved SIC architecture is also proposed.Finally, this paper gives an analysis of the characteristic of the channel in the MIMO system with asynchronous transmission mode in detail. We first get the sufficient statistics and the corresponding mathematical expression of the asynchronous MIMO system by deriving the maximum likelihood(ML) detection directly from the original continuous, unsampled signals at receive antennas. Then, we analyse the capacity and the optimal diversity-multiplexing tradeoff in the MIMO system with asynchronous transmission mode based on the mathematical expression. Finally, a simple architecture of space-time code is proposed which can achieve the optimal diversity-multiplexing tradeoff of this synchronous MIMO system.The research in this thesis extends the existing researches on detection in the V-BLAST system with asynchronous transmission mode, and explores the fundamental of the key characteristic of the channel and space-time coding in the MIMO system with asynchronous transmission mode. The results have some theoretical and practical values.