Showing papers by "Giorgio M. Vitetta published in 2002"

Further results on Tarokh's space-time differential technique

Abstract: Novel results on the space-time differential detection technique described by V Tarokh and H Jafarkhani (see IEEE J Select Areas Commun, vol18, no7, p1169-74, 2000) are derived First, the optimality of the one-shot detection algorithm proposed by Tarokh and Jafarkhani is proved under some assumptions about the channel model and an accurate bit error rate formula for this detector is derived in a particular case Finally, a per-survivor processing (PSP) receiver, substantially outperforming Tarokh's detector, is derived Numerical results show both the superiority of the PSP receiver over the one-shot detector and the accuracy of the above mentioned error rate formula

Equalization Techniques for mitigating transmission impairments

Abstract: Publisher Summary This chapter discusses equalization technique, which is an electronic means for improving performance using equalizer circuits in the receiving terminal, which in principle, can be added for upgrading an existing system. Equalization is used in lightwave systems to significantly increase the data rate and reduce the effect of transmission impairments and thus, improve performance. The chapter illustrates the challenges encountered in lightwave applications and surveys the mathematical techniques that can be employed for mitigating many of the impairments. The chapter also describes recent experimental implementations of equalizers. It is noted that the linear equalizer (LE) and the decision feedback equalizer (DFE) equalization algorithms are commonly derived assuming a known channel impulse response (CIR). Such equalization algorithms learn the channel state in the training period during which a known data sequence is transmitted. It is also observed that an equalizer can compensate for channel distortion even in the absence of known symbols, by using blind deconvolution algorithms.

BEM-based SISO detection of space-time block coded signals transmitted over frequency-flat fading channels

Abstract: In this paper the expectation-maximization (EM) algorithm for maximum a posteriori (MAP) estimation of a random vector is applied to the problem of detection of space-time block coded (STBC) signals over time-selective Rayleigh fading channels. This results in a soft-in soft-out (SISO) detection algorithm suitable for iterative detection/decoding schemes. Simulation results show that the error performance of the proposed detection algorithm is very close to that of a MAP detector endowed with an ideal knowledge of the channel state if the fading rate is not too fast.

BEM-based multiuser detection for synchronous DS-CDMA systems over frequency flat fading channels

Abstract: A soft-input soft-output (SISO) multiuser detection algorithm for synchronous direct sequence-code division multiple access (DS-CDMA) systems operating over a slow Rayleigh fading channel is illustrated. Its derivation is based on the Bayesian expectation maximization (BEM) technique. The proposed detector estimates the fading channel in an iterative fashion and produces the a posteriori probabilities (APPs) of the transmitted symbols. Its error performance is assessed by computer simulation and is compared with that provided by other multiuser detectors.