S. Marapodi’s research while affiliated with University of Florence and other places

This paper proposes a low complexity joint space-time multiuser detection algorithm for asynchronous DS/CDMA antenna array systems. The proposed multiuser detector is composed of an adaptive antenna array, used as a linear beamformer, and a sliding window decorrelator. A QPSK modulation scheme is used in order to increase bandwidth efficiency. Numerical results are given in terms of Bit Error Rate (BER) under the assumption of a frequency-selective Rayleigh slow fading channel. In particular, the proposed receiver is shown to be near-far resistant, even in worst fading cases, and to exploit completely array introduction while maintaining acceptable computational complexity. The proposed architecture avoids linear filter realization of the decorrelator, which is impractical in the case of a large number of users, and operates with relatively short data frames instead of the complete information sequence. Finally, this receiver is very flexible to changes in timing configuration.

The paper describes a joint azimuthal and elevational directions-of-arrival estimation method by using an uniform circular array at the base station in the up-link of the UMTS system. The performance of conventional direction-finding algorithms (such as MUSIC) decreases in this scenario due to high number of signals impinging on the antenna array certainly higher than the number of array elements. The proposed approach overcomes this constraint and allows to provide unique estimates even with a high number of UMTS active users in fading multipath propagation environment.

The paper describes the application of multiple signal classification (MUSIC) and its derivative algorithms to the estimation of direction of arrival (DOA) of multipath signals received from multiple users on the uplink of a wideband direct sequence code division multiple access (wideband DS-CDMA) system. Due to the multiple-access interference (MAI) and multipath, a high number of signals impinge on the antenna array and this scenario causes conventional direction-finding algorithms (such as MUSIC) to fail. The proposed approach extends the use of MUSIC and allows to provide unique estimates even when the number of DOAs exceeds the number of antenna array elements.

This paper deals with a multiuser detector for DS-CDMA wireless communication systems. The proposed detector's main feature lies in the joint utilization of the space and time processing techniques since adaptive antenna arrays and decorrelating multiuser receiver are supposed to be used together. The complexity growth is lowered by implementing a multiuser detection technique based on the sliding window algorithm. The DS-CDMA communication system considered resorts to QPSK modulated wideband signals so that a sliding window algorithm generalization is necessary. The simulation results shown here confirm that the proposed structure is near-far resistant even in the worst fading cases. As the sensor number increases a remarkable performance improvement takes place. Besides we show that the proposed receiver allows systems to exploit completely the array introduction while maintaining an acceptable computational complexity

This paper deals with a multiuser detector for DS-CDMA wireless communication systems. The proposed detector's main feature lies in the joint utilization of the space and time processing techniques since adaptive antenna arrays and decorrelating multiuser receiver are supposed to be used together. Complexity growth is lowered by implementing a multiuser detection technique based on the sliding window algorithm. The DS-CDMA communication system considered resorts to QPSK modulated wideband signals so that a sliding window algorithm generalization is necessary. The simulation results shown here confirm that the proposed structure is near-far resistant even in the worst fading cases. As the sensor number increases a remarkable performance improvement takes place. Besides we show that the proposed receiver allows systems to exploit completely the array introduction while maintaining an acceptable computational complexity