Search

SUMMARY Multiple-input and multiple-output detectors may rely on the complex and real signal models, yielding complex detectors for quadrature amplitude modulated signals and real detectors for pulse amplitude modulated signals, respectively. It is well-known that the complex and real maximum likelihood detectors are equivalent. But relying on both the conventional real and pairwise real models, we show in this paper that some of the suboptimal real detectors are equivalent to their counterpart complex detectors, whereas some are not. The equivalence between the complex and pairwise real detectors also leads us to develop fast preprocessing algorithms for the real ordered successive interference cancelation and tree search detectors. Finally, we show that the preprocessing computations required by the equivalent suboptimal complex and pairwise real detectors are of the same complexity. When some practical preprocessing criteria are used, the real detectors may not detect the PAM signals in the pairwise manner. Such non-pairwise real detectors outperform their counterpart complex detectors at the cost of higher preprocessing complexity. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY For practical consideration, efficient and stable implementation of the promising vertical Bell Labs Layered Space-Time system is highly desirable. The original square-root algorithm (SRA), proposed by Hassibi, for the minimum mean square error detection, is composed of three stages, that is, initialization, ordering, and nulling. Unlike the original SRA whose initialization stage is not completely based on unitary transformations, the three stages of our proposed algorithm #1 are all based on unitary transformations. The average number of multiplications required by our proposed algorithm #1 is about (29∕10) M3, where both the numbers of transmit and receive antennas are equal to M. In the meantime, the average number of multiplications required by the original SRA is (17∕3) M3. In addition to the stable initialization, ordering, and nulling considered by the proposed algorithm #1, our proposed algorithm #2 considers stable detection. Our proposed algorithm #2 is completely based on Givens rotations, which is to be implemented by COordinate Rotation DIgital Computer-based hardwares. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]