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An algorithm for blind source separation is introduced, that is free of undesired stationary points in arbitrary number of user signals, is proposed.

Recently, a novel MIMO transmitter architecture has been introduced that requires only a single radio-frequency (RF) chain and is built on parasitic antenna arrays. MIMO transmission in this case is achieved by shaping directly the radiation pattern with the aid of analog tunable loads attached to the parasitics. As it has been shown, such a single RF MIMO system can support all PSK modulation formats with purely imaginary loading values. This paper extends its capabilities and proposes a novel architecture for parasitic antennas that is able to provide complex loading values, even with a negative real part. Definitely, this will extend the flexibility of parasitic antennas to multiplex successfully over the air more complex signaling formats, for example, QAM signals. The bit error rate evaluation shows that the proposed architecture could be very promising in emerging devices and also illustrates its robustness under possible loading perturbations that might have been raised due to nonidealities in the design. [ABSTRACT FROM AUTHOR]

The problem of linear equalization of polyphase channels and its blind implementation were examined. The channels may result from oversampling the single output of a transmission circuit and/or by receiving multiple outputs of an antenna array. Optimal settings of different well-known types of linear equalization structures were derived blindly using only the output's second-order statistics via multichannel linear prediction or related methods.

In this paper we introduce a new perspective the implementation of wireless MIMO transmission systems with increased bandwidth efficiency. Unlike traditional spatial multiplexing techniques in MIMO systems, where additional information can be sent through the wireless channel by feeding uncorrelated antenna elements with diverse bitstreams, we use the idea of mapping diverse bitstreams onto orthogonal bases defined in the beamspace domain of the transmitting array far-field region. Using this approach we show that we can increase the capacity of wireless communication systems using compact parasitic antenna architectures and a single RF front end at transmitter, thus paving the way for integrating MIMO systems in cost and size sensitive wireless devices such as mobile terminals and mobile personal digital assistants. [ABSTRACT FROM AUTHOR]

The problem of pilot and data channel mismatch in a steered space-time spreading (SSTS) system is addressed by means of advanced signal processing at the mobile receiver. The main idea is to apply the SSTS antenna array architecture and transmission algorithm and involve both the pilot and traffic signals in channel estimation at the receiver. Two semiblind algorithms are compared with the conventional pilot-based receiver in a CDMA2000-1X RC3 environment by means of simulations with variable speed and spatial angular spread, taking into account main imperfections such as estimation error for the correlation coefficient at the reverse link, calibration error, and different pilot powers for diversity antennas. It is demonstrated that the semiblind algorithms outperform the conventional receiver in the low, and medium-speed area. [ABSTRACT FROM AUTHOR]

It is shown that single symbol maximum-likelihood (ML) decoding for chosen rate 6/8 linear complex space-time codes for up to eight transmit antennas is possible in the presence of a phase feedback. The performance of the code is the same as that of an ideal code, for which the sufficient statistic of the channel is its Frobenius norm. For rate 1 codes for up to eight antennas, a two-phase feedback enables a symbol to see the interference from only one symbol instead of three, thereby reducing the complexity of ML decoding. Quantization of the feedback is also considered. [ABSTRACT FROM AUTHOR]

In this paper, we address the problem of unsupervised (blind) space-time equalization of frequency-selective multiple-input multiple-output (MIMO) channels. The motivation behind this work is that in order to provide the high transmission rates that data-demanding applications require, wireless multiple antenna (MIMO) systems will have to operate in wide bandwidths. In such scenarios, frequency selectivity may induce important intersymbol interference (ISI), in addition to the interuser interference (IUI) that each antenna's transmitted stream of data suffers from the other antennas. Under these conditions, channel estimation of the frequency-selective MIMO channel may become a daunting task that ultimately reduces the effective transmission rate. We present a family of globally convergent blind space-time equalization techniques, developed from multiuser kurtosis output-based criteria, which allow the recovery of the MIMO channel inputs without the training overhead that channel estimation typically requires, thus improving the MIMO channel's spectral efficiency. [ABSTRACT FROM AUTHOR]

The design of space-time codes that are capable of approaching the capacity of multiple-input-single-output (MISO) antenna systems is a challenging problem, yet one of high practical importance. While a remarkably simple scheme of Alamouti is capable of attaining the channel capacity in the case of two-transmitter and one-receiver antennas (2, 1), no such schemes are known for the case of more than two transmitter antennas. In this correspondence, we propose a family of space-time codes that are especially designed for the case of four-transmitter antennas and that are shown to allow the attainment of a significant fraction of the open-loop Shannon capacity of the (4, 1) channel. [ABSTRACT FROM AUTHOR]

In this letter, we show that the performance of recently proposed quasi-orthogonal space-time codes can be improved by phase-shifting the constellations of the symbols constituting the code. The optimal rotation of the symbols increases the minimum distance of the corresponding space-time codewords, leading to substantially improved performance. [ABSTRACT FROM AUTHOR]

Presents a study which examined the use of multiple antenna receivers that combine space-time (ST) processing with multi-user detection as an alternative for the detection of synchronous code division multiple access signals in multipath channels. Description of the received signal model; Adaptive implementations of the ST-minimum mean-squared error detector; Numerical results.